/*
 *  Overview:
 *   This is the generic MTD driver for NAND flash devices. It should be
 *   capable of working with almost all NAND chips currently available.
 *
 *	Additional technical information is available on
 *	http://www.linux-mtd.infradead.org/doc/nand.html
 *
 *  Copyright (C) 2000 Steven J. Hill (sjhill@realitydiluted.com)
 *		  2002-2006 Thomas Gleixner (tglx@linutronix.de)
 *
 *  Credits:
 *	David Woodhouse for adding multichip support
 *
 *	Aleph One Ltd. and Toby Churchill Ltd. for supporting the
 *	rework for 2K page size chips
 *
 *  TODO:
 *	Enable cached programming for 2k page size chips
 *	Check, if mtd->ecctype should be set to MTD_ECC_HW
 *	if we have HW ECC support.
 *	BBT table is not serialized, has to be fixed
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/nmi.h>
#include <linux/types.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/rawnand.h>
#include <linux/mtd/nand_ecc.h>
#include <linux/mtd/nand_bch.h>
#include <linux/interrupt.h>
#include <linux/bitops.h>
#include <linux/io.h>
#include <linux/mtd/partitions.h>
#include <linux/of.h>

static int nand_get_device(struct mtd_info *mtd, int new_state);

static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
			     struct mtd_oob_ops *ops);

/* Define default oob placement schemes for large and small page devices */
static int nand_ooblayout_ecc_sp(struct mtd_info *mtd, int section,
				 struct mtd_oob_region *oobregion)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct nand_ecc_ctrl *ecc = &chip->ecc;

	if (section > 1)
		return -ERANGE;

	if (!section) {
		oobregion->offset = 0;
		if (mtd->oobsize == 16)
			oobregion->length = 4;
		else
			oobregion->length = 3;
	} else {
		if (mtd->oobsize == 8)
			return -ERANGE;

		oobregion->offset = 6;
		oobregion->length = ecc->total - 4;
	}

	return 0;
}

static int nand_ooblayout_free_sp(struct mtd_info *mtd, int section,
				  struct mtd_oob_region *oobregion)
{
	if (section > 1)
		return -ERANGE;

	if (mtd->oobsize == 16) {
		if (section)
			return -ERANGE;

		oobregion->length = 8;
		oobregion->offset = 8;
	} else {
		oobregion->length = 2;
		if (!section)
			oobregion->offset = 3;
		else
			oobregion->offset = 6;
	}

	return 0;
}

const struct mtd_ooblayout_ops nand_ooblayout_sp_ops = {
	.ecc = nand_ooblayout_ecc_sp,
	.free = nand_ooblayout_free_sp,
};
EXPORT_SYMBOL_GPL(nand_ooblayout_sp_ops);

static int nand_ooblayout_ecc_lp(struct mtd_info *mtd, int section,
				 struct mtd_oob_region *oobregion)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct nand_ecc_ctrl *ecc = &chip->ecc;

	if (section || !ecc->total)
		return -ERANGE;

	oobregion->length = ecc->total;
	oobregion->offset = mtd->oobsize - oobregion->length;

	return 0;
}

static int nand_ooblayout_free_lp(struct mtd_info *mtd, int section,
				  struct mtd_oob_region *oobregion)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct nand_ecc_ctrl *ecc = &chip->ecc;

	if (section)
		return -ERANGE;

	oobregion->length = mtd->oobsize - ecc->total - 2;
	oobregion->offset = 2;

	return 0;
}

const struct mtd_ooblayout_ops nand_ooblayout_lp_ops = {
	.ecc = nand_ooblayout_ecc_lp,
	.free = nand_ooblayout_free_lp,
};
EXPORT_SYMBOL_GPL(nand_ooblayout_lp_ops);

/*
 * Support the old "large page" layout used for 1-bit Hamming ECC where ECC
 * are placed at a fixed offset.
 */
static int nand_ooblayout_ecc_lp_hamming(struct mtd_info *mtd, int section,
					 struct mtd_oob_region *oobregion)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct nand_ecc_ctrl *ecc = &chip->ecc;

	if (section)
		return -ERANGE;

	switch (mtd->oobsize) {
	case 64:
		oobregion->offset = 40;
		break;
	case 128:
		oobregion->offset = 80;
		break;
	default:
		return -EINVAL;
	}

	oobregion->length = ecc->total;
	if (oobregion->offset + oobregion->length > mtd->oobsize)
		return -ERANGE;

	return 0;
}

static int nand_ooblayout_free_lp_hamming(struct mtd_info *mtd, int section,
					  struct mtd_oob_region *oobregion)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int ecc_offset = 0;

	if (section < 0 || section > 1)
		return -ERANGE;

	switch (mtd->oobsize) {
	case 64:
		ecc_offset = 40;
		break;
	case 128:
		ecc_offset = 80;
		break;
	default:
		return -EINVAL;
	}

	if (section == 0) {
		oobregion->offset = 2;
		oobregion->length = ecc_offset - 2;
	} else {
		oobregion->offset = ecc_offset + ecc->total;
		oobregion->length = mtd->oobsize - oobregion->offset;
	}

	return 0;
}

static const struct mtd_ooblayout_ops nand_ooblayout_lp_hamming_ops = {
	.ecc = nand_ooblayout_ecc_lp_hamming,
	.free = nand_ooblayout_free_lp_hamming,
};

static int check_offs_len(struct mtd_info *mtd,
					loff_t ofs, uint64_t len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	int ret = 0;

	/* Start address must align on block boundary */
	if (ofs & ((1ULL << chip->phys_erase_shift) - 1)) {
		pr_debug("%s: unaligned address\n", __func__);
		ret = -EINVAL;
	}

	/* Length must align on block boundary */
	if (len & ((1ULL << chip->phys_erase_shift) - 1)) {
		pr_debug("%s: length not block aligned\n", __func__);
		ret = -EINVAL;
	}

	return ret;
}

/**
 * nand_release_device - [GENERIC] release chip
 * @mtd: MTD device structure
 *
 * Release chip lock and wake up anyone waiting on the device.
 */
static void nand_release_device(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	/* Release the controller and the chip */
	spin_lock(&chip->controller->lock);
	chip->controller->active = NULL;
	chip->state = FL_READY;
	wake_up(&chip->controller->wq);
	spin_unlock(&chip->controller->lock);
}

/**
 * nand_read_byte - [DEFAULT] read one byte from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 8bit buswidth
 */
static uint8_t nand_read_byte(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	return readb(chip->IO_ADDR_R);
}

/**
 * nand_read_byte16 - [DEFAULT] read one byte endianness aware from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 16bit buswidth with endianness conversion.
 *
 */
static uint8_t nand_read_byte16(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	return (uint8_t) cpu_to_le16(readw(chip->IO_ADDR_R));
}

/**
 * nand_read_word - [DEFAULT] read one word from the chip
 * @mtd: MTD device structure
 *
 * Default read function for 16bit buswidth without endianness conversion.
 */
static u16 nand_read_word(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	return readw(chip->IO_ADDR_R);
}

/**
 * nand_select_chip - [DEFAULT] control CE line
 * @mtd: MTD device structure
 * @chipnr: chipnumber to select, -1 for deselect
 *
 * Default select function for 1 chip devices.
 */
static void nand_select_chip(struct mtd_info *mtd, int chipnr)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	switch (chipnr) {
	case -1:
		chip->cmd_ctrl(mtd, NAND_CMD_NONE, 0 | NAND_CTRL_CHANGE);
		break;
	case 0:
		break;

	default:
		BUG();
	}
}

/**
 * nand_write_byte - [DEFAULT] write single byte to chip
 * @mtd: MTD device structure
 * @byte: value to write
 *
 * Default function to write a byte to I/O[7:0]
 */
static void nand_write_byte(struct mtd_info *mtd, uint8_t byte)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	chip->write_buf(mtd, &byte, 1);
}

/**
 * nand_write_byte16 - [DEFAULT] write single byte to a chip with width 16
 * @mtd: MTD device structure
 * @byte: value to write
 *
 * Default function to write a byte to I/O[7:0] on a 16-bit wide chip.
 */
static void nand_write_byte16(struct mtd_info *mtd, uint8_t byte)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	uint16_t word = byte;

	/*
	 * It's not entirely clear what should happen to I/O[15:8] when writing
	 * a byte. The ONFi spec (Revision 3.1; 2012-09-19, Section 2.16) reads:
	 *
	 *    When the host supports a 16-bit bus width, only data is
	 *    transferred at the 16-bit width. All address and command line
	 *    transfers shall use only the lower 8-bits of the data bus. During
	 *    command transfers, the host may place any value on the upper
	 *    8-bits of the data bus. During address transfers, the host shall
	 *    set the upper 8-bits of the data bus to 00h.
	 *
	 * One user of the write_byte callback is nand_set_features. The
	 * four parameters are specified to be written to I/O[7:0], but this is
	 * neither an address nor a command transfer. Let's assume a 0 on the
	 * upper I/O lines is OK.
	 */
	chip->write_buf(mtd, (uint8_t *)&word, 2);
}

/**
 * nand_write_buf - [DEFAULT] write buffer to chip
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 *
 * Default write function for 8bit buswidth.
 */
static void nand_write_buf(struct mtd_info *mtd, const uint8_t *buf, int len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	iowrite8_rep(chip->IO_ADDR_W, buf, len);
}

/**
 * nand_read_buf - [DEFAULT] read chip data into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 *
 * Default read function for 8bit buswidth.
 */
static void nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	ioread8_rep(chip->IO_ADDR_R, buf, len);
}

/**
 * nand_write_buf16 - [DEFAULT] write buffer to chip
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 *
 * Default write function for 16bit buswidth.
 */
static void nand_write_buf16(struct mtd_info *mtd, const uint8_t *buf, int len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	u16 *p = (u16 *) buf;

	iowrite16_rep(chip->IO_ADDR_W, p, len >> 1);
}

/**
 * nand_read_buf16 - [DEFAULT] read chip data into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 *
 * Default read function for 16bit buswidth.
 */
static void nand_read_buf16(struct mtd_info *mtd, uint8_t *buf, int len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	u16 *p = (u16 *) buf;

	ioread16_rep(chip->IO_ADDR_R, p, len >> 1);
}

/**
 * nand_block_bad - [DEFAULT] Read bad block marker from the chip
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * Check, if the block is bad.
 */
static int nand_block_bad(struct mtd_info *mtd, loff_t ofs)
{
	int page, page_end, res;
	struct nand_chip *chip = mtd_to_nand(mtd);
	u8 bad;

	if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
		ofs += mtd->erasesize - mtd->writesize;

	page = (int)(ofs >> chip->page_shift) & chip->pagemask;
	page_end = page + (chip->bbt_options & NAND_BBT_SCAN2NDPAGE ? 2 : 1);

	for (; page < page_end; page++) {
		res = chip->ecc.read_oob(mtd, chip, page);
		if (res < 0)
			return res;

		bad = chip->oob_poi[chip->badblockpos];

		if (likely(chip->badblockbits == 8))
			res = bad != 0xFF;
		else
			res = hweight8(bad) < chip->badblockbits;
		if (res)
			return res;
	}

	return 0;
}

/**
 * nand_default_block_markbad - [DEFAULT] mark a block bad via bad block marker
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * This is the default implementation, which can be overridden by a hardware
 * specific driver. It provides the details for writing a bad block marker to a
 * block.
 */
static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct mtd_oob_ops ops;
	uint8_t buf[2] = { 0, 0 };
	int ret = 0, res, i = 0;

	memset(&ops, 0, sizeof(ops));
	ops.oobbuf = buf;
	ops.ooboffs = chip->badblockpos;
	if (chip->options & NAND_BUSWIDTH_16) {
		ops.ooboffs &= ~0x01;
		ops.len = ops.ooblen = 2;
	} else {
		ops.len = ops.ooblen = 1;
	}
	ops.mode = MTD_OPS_PLACE_OOB;

	/* Write to first/last page(s) if necessary */
	if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
		ofs += mtd->erasesize - mtd->writesize;
	do {
		res = nand_do_write_oob(mtd, ofs, &ops);
		if (!ret)
			ret = res;

		i++;
		ofs += mtd->writesize;
	} while ((chip->bbt_options & NAND_BBT_SCAN2NDPAGE) && i < 2);

	return ret;
}

/**
 * nand_block_markbad_lowlevel - mark a block bad
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * This function performs the generic NAND bad block marking steps (i.e., bad
 * block table(s) and/or marker(s)). We only allow the hardware driver to
 * specify how to write bad block markers to OOB (chip->block_markbad).
 *
 * We try operations in the following order:
 *
 *  (1) erase the affected block, to allow OOB marker to be written cleanly
 *  (2) write bad block marker to OOB area of affected block (unless flag
 *      NAND_BBT_NO_OOB_BBM is present)
 *  (3) update the BBT
 *
 * Note that we retain the first error encountered in (2) or (3), finish the
 * procedures, and dump the error in the end.
*/
static int nand_block_markbad_lowlevel(struct mtd_info *mtd, loff_t ofs)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	int res, ret = 0;

	if (!(chip->bbt_options & NAND_BBT_NO_OOB_BBM)) {
		struct erase_info einfo;

		/* Attempt erase before marking OOB */
		memset(&einfo, 0, sizeof(einfo));
		einfo.addr = ofs;
		einfo.len = 1ULL << chip->phys_erase_shift;
		nand_erase_nand(mtd, &einfo, 0);

		/* Write bad block marker to OOB */
		nand_get_device(mtd, FL_WRITING);
		ret = chip->block_markbad(mtd, ofs);
		nand_release_device(mtd);
	}

	/* Mark block bad in BBT */
	if (chip->bbt) {
		res = nand_markbad_bbt(mtd, ofs);
		if (!ret)
			ret = res;
	}

	if (!ret)
		mtd->ecc_stats.badblocks++;

	return ret;
}

/**
 * nand_check_wp - [GENERIC] check if the chip is write protected
 * @mtd: MTD device structure
 *
 * Check, if the device is write protected. The function expects, that the
 * device is already selected.
 */
static int nand_check_wp(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	u8 status;
	int ret;

	/* Broken xD cards report WP despite being writable */
	if (chip->options & NAND_BROKEN_XD)
		return 0;

	/* Check the WP bit */
	ret = nand_status_op(chip, &status);
	if (ret)
		return ret;

	return status & NAND_STATUS_WP ? 0 : 1;
}

/**
 * nand_block_isreserved - [GENERIC] Check if a block is marked reserved.
 * @mtd: MTD device structure
 * @ofs: offset from device start
 *
 * Check if the block is marked as reserved.
 */
static int nand_block_isreserved(struct mtd_info *mtd, loff_t ofs)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	if (!chip->bbt)
		return 0;
	/* Return info from the table */
	return nand_isreserved_bbt(mtd, ofs);
}

/**
 * nand_block_checkbad - [GENERIC] Check if a block is marked bad
 * @mtd: MTD device structure
 * @ofs: offset from device start
 * @allowbbt: 1, if its allowed to access the bbt area
 *
 * Check, if the block is bad. Either by reading the bad block table or
 * calling of the scan function.
 */
static int nand_block_checkbad(struct mtd_info *mtd, loff_t ofs, int allowbbt)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	if (!chip->bbt)
		return chip->block_bad(mtd, ofs);

	/* Return info from the table */
	return nand_isbad_bbt(mtd, ofs, allowbbt);
}

/**
 * panic_nand_wait_ready - [GENERIC] Wait for the ready pin after commands.
 * @mtd: MTD device structure
 * @timeo: Timeout
 *
 * Helper function for nand_wait_ready used when needing to wait in interrupt
 * context.
 */
static void panic_nand_wait_ready(struct mtd_info *mtd, unsigned long timeo)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	int i;

	/* Wait for the device to get ready */
	for (i = 0; i < timeo; i++) {
		if (chip->dev_ready(mtd))
			break;
		touch_softlockup_watchdog();
		mdelay(1);
	}
}

/**
 * nand_wait_ready - [GENERIC] Wait for the ready pin after commands.
 * @mtd: MTD device structure
 *
 * Wait for the ready pin after a command, and warn if a timeout occurs.
 */
void nand_wait_ready(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	unsigned long timeo = 400;

	if (in_interrupt() || oops_in_progress)
		return panic_nand_wait_ready(mtd, timeo);

	/* Wait until command is processed or timeout occurs */
	timeo = jiffies + msecs_to_jiffies(timeo);
	do {
		if (chip->dev_ready(mtd))
			return;
		cond_resched();
	} while (time_before(jiffies, timeo));

	if (!chip->dev_ready(mtd))
		pr_warn_ratelimited("timeout while waiting for chip to become ready\n");
}
EXPORT_SYMBOL_GPL(nand_wait_ready);

/**
 * nand_wait_status_ready - [GENERIC] Wait for the ready status after commands.
 * @mtd: MTD device structure
 * @timeo: Timeout in ms
 *
 * Wait for status ready (i.e. command done) or timeout.
 */
static void nand_wait_status_ready(struct mtd_info *mtd, unsigned long timeo)
{
	register struct nand_chip *chip = mtd_to_nand(mtd);
	int ret;

	timeo = jiffies + msecs_to_jiffies(timeo);
	do {
		u8 status;

		ret = nand_read_data_op(chip, &status, sizeof(status), true);
		if (ret)
			return;

		if (status & NAND_STATUS_READY)
			break;
		touch_softlockup_watchdog();
	} while (time_before(jiffies, timeo));
};

/**
 * nand_soft_waitrdy - Poll STATUS reg until RDY bit is set to 1
 * @chip: NAND chip structure
 * @timeout_ms: Timeout in ms
 *
 * Poll the STATUS register using ->exec_op() until the RDY bit becomes 1.
 * If that does not happen whitin the specified timeout, -ETIMEDOUT is
 * returned.
 *
 * This helper is intended to be used when the controller does not have access
 * to the NAND R/B pin.
 *
 * Be aware that calling this helper from an ->exec_op() implementation means
 * ->exec_op() must be re-entrant.
 *
 * Return 0 if the NAND chip is ready, a negative error otherwise.
 */
int nand_soft_waitrdy(struct nand_chip *chip, unsigned long timeout_ms)
{
	const struct nand_sdr_timings *timings;
	u8 status = 0;
	int ret;

	if (!chip->exec_op)
		return -ENOTSUPP;

	/* Wait tWB before polling the STATUS reg. */
	timings = nand_get_sdr_timings(&chip->data_interface);
	ndelay(PSEC_TO_NSEC(timings->tWB_max));

	ret = nand_status_op(chip, NULL);
	if (ret)
		return ret;

	timeout_ms = jiffies + msecs_to_jiffies(timeout_ms);
	do {
		ret = nand_read_data_op(chip, &status, sizeof(status), true);
		if (ret)
			break;

		if (status & NAND_STATUS_READY)
			break;

		/*
		 * Typical lowest execution time for a tR on most NANDs is 10us,
		 * use this as polling delay before doing something smarter (ie.
		 * deriving a delay from the timeout value, timeout_ms/ratio).
		 */
		udelay(10);
	} while	(time_before(jiffies, timeout_ms));

	/*
	 * We have to exit READ_STATUS mode in order to read real data on the
	 * bus in case the WAITRDY instruction is preceding a DATA_IN
	 * instruction.
	 */
	nand_exit_status_op(chip);

	if (ret)
		return ret;

	return status & NAND_STATUS_READY ? 0 : -ETIMEDOUT;
};
EXPORT_SYMBOL_GPL(nand_soft_waitrdy);

/**
 * nand_command - [DEFAULT] Send command to NAND device
 * @mtd: MTD device structure
 * @command: the command to be sent
 * @column: the column address for this command, -1 if none
 * @page_addr: the page address for this command, -1 if none
 *
 * Send command to NAND device. This function is used for small page devices
 * (512 Bytes per page).
 */
static void nand_command(struct mtd_info *mtd, unsigned int command,
			 int column, int page_addr)
{
	register struct nand_chip *chip = mtd_to_nand(mtd);
	int ctrl = NAND_CTRL_CLE | NAND_CTRL_CHANGE;

	/* Write out the command to the device */
	if (command == NAND_CMD_SEQIN) {
		int readcmd;

		if (column >= mtd->writesize) {
			/* OOB area */
			column -= mtd->writesize;
			readcmd = NAND_CMD_READOOB;
		} else if (column < 256) {
			/* First 256 bytes --> READ0 */
			readcmd = NAND_CMD_READ0;
		} else {
			column -= 256;
			readcmd = NAND_CMD_READ1;
		}
		chip->cmd_ctrl(mtd, readcmd, ctrl);
		ctrl &= ~NAND_CTRL_CHANGE;
	}
	if (command != NAND_CMD_NONE)
		chip->cmd_ctrl(mtd, command, ctrl);

	/* Address cycle, when necessary */
	ctrl = NAND_CTRL_ALE | NAND_CTRL_CHANGE;
	/* Serially input address */
	if (column != -1) {
		/* Adjust columns for 16 bit buswidth */
		if (chip->options & NAND_BUSWIDTH_16 &&
				!nand_opcode_8bits(command))
			column >>= 1;
		chip->cmd_ctrl(mtd, column, ctrl);
		ctrl &= ~NAND_CTRL_CHANGE;
	}
	if (page_addr != -1) {
		chip->cmd_ctrl(mtd, page_addr, ctrl);
		ctrl &= ~NAND_CTRL_CHANGE;
		chip->cmd_ctrl(mtd, page_addr >> 8, ctrl);
		if (chip->options & NAND_ROW_ADDR_3)
			chip->cmd_ctrl(mtd, page_addr >> 16, ctrl);
	}
	chip->cmd_ctrl(mtd, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);

	/*
	 * Program and erase have their own busy handlers status and sequential
	 * in needs no delay
	 */
	switch (command) {

	case NAND_CMD_NONE:
	case NAND_CMD_PAGEPROG:
	case NAND_CMD_ERASE1:
	case NAND_CMD_ERASE2:
	case NAND_CMD_SEQIN:
	case NAND_CMD_STATUS:
	case NAND_CMD_READID:
	case NAND_CMD_SET_FEATURES:
		return;

	case NAND_CMD_RESET:
		if (chip->dev_ready)
			break;
		udelay(chip->chip_delay);
		chip->cmd_ctrl(mtd, NAND_CMD_STATUS,
			       NAND_CTRL_CLE | NAND_CTRL_CHANGE);
		chip->cmd_ctrl(mtd,
			       NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);
		/* EZ-NAND can take upto 250ms as per ONFi v4.0 */
		nand_wait_status_ready(mtd, 250);
		return;

		/* This applies to read commands */
	case NAND_CMD_READ0:
		/*
		 * READ0 is sometimes used to exit GET STATUS mode. When this
		 * is the case no address cycles are requested, and we can use
		 * this information to detect that we should not wait for the
		 * device to be ready.
		 */
		if (column == -1 && page_addr == -1)
			return;

	default:
		/*
		 * If we don't have access to the busy pin, we apply the given
		 * command delay
		 */
		if (!chip->dev_ready) {
			udelay(chip->chip_delay);
			return;
		}
	}
	/*
	 * Apply this short delay always to ensure that we do wait tWB in
	 * any case on any machine.
	 */
	ndelay(100);

	nand_wait_ready(mtd);
}

static void nand_ccs_delay(struct nand_chip *chip)
{
	/*
	 * The controller already takes care of waiting for tCCS when the RNDIN
	 * or RNDOUT command is sent, return directly.
	 */
	if (!(chip->options & NAND_WAIT_TCCS))
		return;

	/*
	 * Wait tCCS_min if it is correctly defined, otherwise wait 500ns
	 * (which should be safe for all NANDs).
	 */
	if (chip->setup_data_interface)
		ndelay(chip->data_interface.timings.sdr.tCCS_min / 1000);
	else
		ndelay(500);
}

/**
 * nand_command_lp - [DEFAULT] Send command to NAND large page device
 * @mtd: MTD device structure
 * @command: the command to be sent
 * @column: the column address for this command, -1 if none
 * @page_addr: the page address for this command, -1 if none
 *
 * Send command to NAND device. This is the version for the new large page
 * devices. We don't have the separate regions as we have in the small page
 * devices. We must emulate NAND_CMD_READOOB to keep the code compatible.
 */
static void nand_command_lp(struct mtd_info *mtd, unsigned int command,
			    int column, int page_addr)
{
	register struct nand_chip *chip = mtd_to_nand(mtd);

	/* Emulate NAND_CMD_READOOB */
	if (command == NAND_CMD_READOOB) {
		column += mtd->writesize;
		command = NAND_CMD_READ0;
	}

	/* Command latch cycle */
	if (command != NAND_CMD_NONE)
		chip->cmd_ctrl(mtd, command,
			       NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);

	if (column != -1 || page_addr != -1) {
		int ctrl = NAND_CTRL_CHANGE | NAND_NCE | NAND_ALE;

		/* Serially input address */
		if (column != -1) {
			/* Adjust columns for 16 bit buswidth */
			if (chip->options & NAND_BUSWIDTH_16 &&
					!nand_opcode_8bits(command))
				column >>= 1;
			chip->cmd_ctrl(mtd, column, ctrl);
			ctrl &= ~NAND_CTRL_CHANGE;

			/* Only output a single addr cycle for 8bits opcodes. */
			if (!nand_opcode_8bits(command))
				chip->cmd_ctrl(mtd, column >> 8, ctrl);
		}
		if (page_addr != -1) {
			chip->cmd_ctrl(mtd, page_addr, ctrl);
			chip->cmd_ctrl(mtd, page_addr >> 8,
				       NAND_NCE | NAND_ALE);
			if (chip->options & NAND_ROW_ADDR_3)
				chip->cmd_ctrl(mtd, page_addr >> 16,
					       NAND_NCE | NAND_ALE);
		}
	}
	chip->cmd_ctrl(mtd, NAND_CMD_NONE, NAND_NCE | NAND_CTRL_CHANGE);

	/*
	 * Program and erase have their own busy handlers status, sequential
	 * in and status need no delay.
	 */
	switch (command) {

	case NAND_CMD_NONE:
	case NAND_CMD_CACHEDPROG:
	case NAND_CMD_PAGEPROG:
	case NAND_CMD_ERASE1:
	case NAND_CMD_ERASE2:
	case NAND_CMD_SEQIN:
	case NAND_CMD_STATUS:
	case NAND_CMD_READID:
	case NAND_CMD_SET_FEATURES:
		return;

	case NAND_CMD_RNDIN:
		nand_ccs_delay(chip);
		return;

	case NAND_CMD_RESET:
		if (chip->dev_ready)
			break;
		udelay(chip->chip_delay);
		chip->cmd_ctrl(mtd, NAND_CMD_STATUS,
			       NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
		chip->cmd_ctrl(mtd, NAND_CMD_NONE,
			       NAND_NCE | NAND_CTRL_CHANGE);
		/* EZ-NAND can take upto 250ms as per ONFi v4.0 */
		nand_wait_status_ready(mtd, 250);
		return;

	case NAND_CMD_RNDOUT:
		/* No ready / busy check necessary */
		chip->cmd_ctrl(mtd, NAND_CMD_RNDOUTSTART,
			       NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
		chip->cmd_ctrl(mtd, NAND_CMD_NONE,
			       NAND_NCE | NAND_CTRL_CHANGE);

		nand_ccs_delay(chip);
		return;

	case NAND_CMD_READ0:
		/*
		 * READ0 is sometimes used to exit GET STATUS mode. When this
		 * is the case no address cycles are requested, and we can use
		 * this information to detect that READSTART should not be
		 * issued.
		 */
		if (column == -1 && page_addr == -1)
			return;

		chip->cmd_ctrl(mtd, NAND_CMD_READSTART,
			       NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
		chip->cmd_ctrl(mtd, NAND_CMD_NONE,
			       NAND_NCE | NAND_CTRL_CHANGE);

		/* This applies to read commands */
	default:
		/*
		 * If we don't have access to the busy pin, we apply the given
		 * command delay.
		 */
		if (!chip->dev_ready) {
			udelay(chip->chip_delay);
			return;
		}
	}

	/*
	 * Apply this short delay always to ensure that we do wait tWB in
	 * any case on any machine.
	 */
	ndelay(100);

	nand_wait_ready(mtd);
}

/**
 * panic_nand_get_device - [GENERIC] Get chip for selected access
 * @chip: the nand chip descriptor
 * @mtd: MTD device structure
 * @new_state: the state which is requested
 *
 * Used when in panic, no locks are taken.
 */
static void panic_nand_get_device(struct nand_chip *chip,
		      struct mtd_info *mtd, int new_state)
{
	/* Hardware controller shared among independent devices */
	chip->controller->active = chip;
	chip->state = new_state;
}

/**
 * nand_get_device - [GENERIC] Get chip for selected access
 * @mtd: MTD device structure
 * @new_state: the state which is requested
 *
 * Get the device and lock it for exclusive access
 */
static int
nand_get_device(struct mtd_info *mtd, int new_state)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	spinlock_t *lock = &chip->controller->lock;
	wait_queue_head_t *wq = &chip->controller->wq;
	DECLARE_WAITQUEUE(wait, current);
retry:
	spin_lock(lock);

	/* Hardware controller shared among independent devices */
	if (!chip->controller->active)
		chip->controller->active = chip;

	if (chip->controller->active == chip && chip->state == FL_READY) {
		chip->state = new_state;
		spin_unlock(lock);
		return 0;
	}
	if (new_state == FL_PM_SUSPENDED) {
		if (chip->controller->active->state == FL_PM_SUSPENDED) {
			chip->state = FL_PM_SUSPENDED;
			spin_unlock(lock);
			return 0;
		}
	}
	set_current_state(TASK_UNINTERRUPTIBLE);
	add_wait_queue(wq, &wait);
	spin_unlock(lock);
	schedule();
	remove_wait_queue(wq, &wait);
	goto retry;
}

/**
 * panic_nand_wait - [GENERIC] wait until the command is done
 * @mtd: MTD device structure
 * @chip: NAND chip structure
 * @timeo: timeout
 *
 * Wait for command done. This is a helper function for nand_wait used when
 * we are in interrupt context. May happen when in panic and trying to write
 * an oops through mtdoops.
 */
static void panic_nand_wait(struct mtd_info *mtd, struct nand_chip *chip,
			    unsigned long timeo)
{
	int i;
	for (i = 0; i < timeo; i++) {
		if (chip->dev_ready) {
			if (chip->dev_ready(mtd))
				break;
		} else {
			int ret;
			u8 status;

			ret = nand_read_data_op(chip, &status, sizeof(status),
						true);
			if (ret)
				return;

			if (status & NAND_STATUS_READY)
				break;
		}
		mdelay(1);
	}
}

/**
 * nand_wait - [DEFAULT] wait until the command is done
 * @mtd: MTD device structure
 * @chip: NAND chip structure
 *
 * Wait for command done. This applies to erase and program only.
 */
static int nand_wait(struct mtd_info *mtd, struct nand_chip *chip)
{

	unsigned long timeo = 400;
	u8 status;
	int ret;

	/*
	 * Apply this short delay always to ensure that we do wait tWB in any
	 * case on any machine.
	 */
	ndelay(100);

	ret = nand_status_op(chip, NULL);
	if (ret)
		return ret;

	if (in_interrupt() || oops_in_progress)
		panic_nand_wait(mtd, chip, timeo);
	else {
		timeo = jiffies + msecs_to_jiffies(timeo);
		do {
			if (chip->dev_ready) {
				if (chip->dev_ready(mtd))
					break;
			} else {
				ret = nand_read_data_op(chip, &status,
							sizeof(status), true);
				if (ret)
					return ret;

				if (status & NAND_STATUS_READY)
					break;
			}
			cond_resched();
		} while (time_before(jiffies, timeo));
	}

	ret = nand_read_data_op(chip, &status, sizeof(status), true);
	if (ret)
		return ret;

	/* This can happen if in case of timeout or buggy dev_ready */
	WARN_ON(!(status & NAND_STATUS_READY));
	return status;
}

static bool nand_supports_get_features(struct nand_chip *chip, int addr)
{
	return (chip->parameters.supports_set_get_features &&
		test_bit(addr, chip->parameters.get_feature_list));
}

static bool nand_supports_set_features(struct nand_chip *chip, int addr)
{
	return (chip->parameters.supports_set_get_features &&
		test_bit(addr, chip->parameters.set_feature_list));
}

/**
 * nand_get_features - wrapper to perform a GET_FEATURE
 * @chip: NAND chip info structure
 * @addr: feature address
 * @subfeature_param: the subfeature parameters, a four bytes array
 *
 * Returns 0 for success, a negative error otherwise. Returns -ENOTSUPP if the
 * operation cannot be handled.
 */
int nand_get_features(struct nand_chip *chip, int addr,
		      u8 *subfeature_param)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (!nand_supports_get_features(chip, addr))
		return -ENOTSUPP;

	return chip->get_features(mtd, chip, addr, subfeature_param);
}
EXPORT_SYMBOL_GPL(nand_get_features);

/**
 * nand_set_features - wrapper to perform a SET_FEATURE
 * @chip: NAND chip info structure
 * @addr: feature address
 * @subfeature_param: the subfeature parameters, a four bytes array
 *
 * Returns 0 for success, a negative error otherwise. Returns -ENOTSUPP if the
 * operation cannot be handled.
 */
int nand_set_features(struct nand_chip *chip, int addr,
		      u8 *subfeature_param)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (!nand_supports_set_features(chip, addr))
		return -ENOTSUPP;

	return chip->set_features(mtd, chip, addr, subfeature_param);
}
EXPORT_SYMBOL_GPL(nand_set_features);

/**
 * nand_reset_data_interface - Reset data interface and timings
 * @chip: The NAND chip
 * @chipnr: Internal die id
 *
 * Reset the Data interface and timings to ONFI mode 0.
 *
 * Returns 0 for success or negative error code otherwise.
 */
static int nand_reset_data_interface(struct nand_chip *chip, int chipnr)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	int ret;

	if (!chip->setup_data_interface)
		return 0;

	/*
	 * The ONFI specification says:
	 * "
	 * To transition from NV-DDR or NV-DDR2 to the SDR data
	 * interface, the host shall use the Reset (FFh) command
	 * using SDR timing mode 0. A device in any timing mode is
	 * required to recognize Reset (FFh) command issued in SDR
	 * timing mode 0.
	 * "
	 *
	 * Configure the data interface in SDR mode and set the
	 * timings to timing mode 0.
	 */

	onfi_fill_data_interface(chip, NAND_SDR_IFACE, 0);
	ret = chip->setup_data_interface(mtd, chipnr, &chip->data_interface);
	if (ret)
		pr_err("Failed to configure data interface to SDR timing mode 0\n");

	return ret;
}

/**
 * nand_setup_data_interface - Setup the best data interface and timings
 * @chip: The NAND chip
 * @chipnr: Internal die id
 *
 * Find and configure the best data interface and NAND timings supported by
 * the chip and the driver.
 * First tries to retrieve supported timing modes from ONFI information,
 * and if the NAND chip does not support ONFI, relies on the
 * ->onfi_timing_mode_default specified in the nand_ids table.
 *
 * Returns 0 for success or negative error code otherwise.
 */
static int nand_setup_data_interface(struct nand_chip *chip, int chipnr)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	u8 tmode_param[ONFI_SUBFEATURE_PARAM_LEN] = {
		chip->onfi_timing_mode_default,
	};
	int ret;

	if (!chip->setup_data_interface)
		return 0;

	/* Change the mode on the chip side (if supported by the NAND chip) */
	if (nand_supports_set_features(chip, ONFI_FEATURE_ADDR_TIMING_MODE)) {
		chip->select_chip(mtd, chipnr);
		ret = nand_set_features(chip, ONFI_FEATURE_ADDR_TIMING_MODE,
					tmode_param);
		chip->select_chip(mtd, -1);
		if (ret)
			return ret;
	}

	/* Change the mode on the controller side */
	ret = chip->setup_data_interface(mtd, chipnr, &chip->data_interface);
	if (ret)
		return ret;

	/* Check the mode has been accepted by the chip, if supported */
	if (!nand_supports_get_features(chip, ONFI_FEATURE_ADDR_TIMING_MODE))
		return 0;

	memset(tmode_param, 0, ONFI_SUBFEATURE_PARAM_LEN);
	chip->select_chip(mtd, chipnr);
	ret = nand_get_features(chip, ONFI_FEATURE_ADDR_TIMING_MODE,
				tmode_param);
	chip->select_chip(mtd, -1);
	if (ret)
		goto err_reset_chip;

	if (tmode_param[0] != chip->onfi_timing_mode_default) {
		pr_warn("timing mode %d not acknowledged by the NAND chip\n",
			chip->onfi_timing_mode_default);
		goto err_reset_chip;
	}

	return 0;

err_reset_chip:
	/*
	 * Fallback to mode 0 if the chip explicitly did not ack the chosen
	 * timing mode.
	 */
	nand_reset_data_interface(chip, chipnr);
	chip->select_chip(mtd, chipnr);
	nand_reset_op(chip);
	chip->select_chip(mtd, -1);

	return ret;
}

/**
 * nand_init_data_interface - find the best data interface and timings
 * @chip: The NAND chip
 *
 * Find the best data interface and NAND timings supported by the chip
 * and the driver.
 * First tries to retrieve supported timing modes from ONFI information,
 * and if the NAND chip does not support ONFI, relies on the
 * ->onfi_timing_mode_default specified in the nand_ids table. After this
 * function nand_chip->data_interface is initialized with the best timing mode
 * available.
 *
 * Returns 0 for success or negative error code otherwise.
 */
static int nand_init_data_interface(struct nand_chip *chip)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	int modes, mode, ret;

	if (!chip->setup_data_interface)
		return 0;

	/*
	 * First try to identify the best timings from ONFI parameters and
	 * if the NAND does not support ONFI, fallback to the default ONFI
	 * timing mode.
	 */
	modes = onfi_get_async_timing_mode(chip);
	if (modes == ONFI_TIMING_MODE_UNKNOWN) {
		if (!chip->onfi_timing_mode_default)
			return 0;

		modes = GENMASK(chip->onfi_timing_mode_default, 0);
	}


	for (mode = fls(modes) - 1; mode >= 0; mode--) {
		ret = onfi_fill_data_interface(chip, NAND_SDR_IFACE, mode);
		if (ret)
			continue;

		/*
		 * Pass NAND_DATA_IFACE_CHECK_ONLY to only check if the
		 * controller supports the requested timings.
		 */
		ret = chip->setup_data_interface(mtd,
						 NAND_DATA_IFACE_CHECK_ONLY,
						 &chip->data_interface);
		if (!ret) {
			chip->onfi_timing_mode_default = mode;
			break;
		}
	}

	return 0;
}

/**
 * nand_fill_column_cycles - fill the column cycles of an address
 * @chip: The NAND chip
 * @addrs: Array of address cycles to fill
 * @offset_in_page: The offset in the page
 *
 * Fills the first or the first two bytes of the @addrs field depending
 * on the NAND bus width and the page size.
 *
 * Returns the number of cycles needed to encode the column, or a negative
 * error code in case one of the arguments is invalid.
 */
static int nand_fill_column_cycles(struct nand_chip *chip, u8 *addrs,
				   unsigned int offset_in_page)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	/* Make sure the offset is less than the actual page size. */
	if (offset_in_page > mtd->writesize + mtd->oobsize)
		return -EINVAL;

	/*
	 * On small page NANDs, there's a dedicated command to access the OOB
	 * area, and the column address is relative to the start of the OOB
	 * area, not the start of the page. Asjust the address accordingly.
	 */
	if (mtd->writesize <= 512 && offset_in_page >= mtd->writesize)
		offset_in_page -= mtd->writesize;

	/*
	 * The offset in page is expressed in bytes, if the NAND bus is 16-bit
	 * wide, then it must be divided by 2.
	 */
	if (chip->options & NAND_BUSWIDTH_16) {
		if (WARN_ON(offset_in_page % 2))
			return -EINVAL;

		offset_in_page /= 2;
	}

	addrs[0] = offset_in_page;

	/*
	 * Small page NANDs use 1 cycle for the columns, while large page NANDs
	 * need 2
	 */
	if (mtd->writesize <= 512)
		return 1;

	addrs[1] = offset_in_page >> 8;

	return 2;
}

static int nand_sp_exec_read_page_op(struct nand_chip *chip, unsigned int page,
				     unsigned int offset_in_page, void *buf,
				     unsigned int len)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	const struct nand_sdr_timings *sdr =
		nand_get_sdr_timings(&chip->data_interface);
	u8 addrs[4];
	struct nand_op_instr instrs[] = {
		NAND_OP_CMD(NAND_CMD_READ0, 0),
		NAND_OP_ADDR(3, addrs, PSEC_TO_NSEC(sdr->tWB_max)),
		NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tR_max),
				 PSEC_TO_NSEC(sdr->tRR_min)),
		NAND_OP_DATA_IN(len, buf, 0),
	};
	struct nand_operation op = NAND_OPERATION(instrs);
	int ret;

	/* Drop the DATA_IN instruction if len is set to 0. */
	if (!len)
		op.ninstrs--;

	if (offset_in_page >= mtd->writesize)
		instrs[0].ctx.cmd.opcode = NAND_CMD_READOOB;
	else if (offset_in_page >= 256 &&
		 !(chip->options & NAND_BUSWIDTH_16))
		instrs[0].ctx.cmd.opcode = NAND_CMD_READ1;

	ret = nand_fill_column_cycles(chip, addrs, offset_in_page);
	if (ret < 0)
		return ret;

	addrs[1] = page;
	addrs[2] = page >> 8;

	if (chip->options & NAND_ROW_ADDR_3) {
		addrs[3] = page >> 16;
		instrs[1].ctx.addr.naddrs++;
	}

	return nand_exec_op(chip, &op);
}

static int nand_lp_exec_read_page_op(struct nand_chip *chip, unsigned int page,
				     unsigned int offset_in_page, void *buf,
				     unsigned int len)
{
	const struct nand_sdr_timings *sdr =
		nand_get_sdr_timings(&chip->data_interface);
	u8 addrs[5];
	struct nand_op_instr instrs[] = {
		NAND_OP_CMD(NAND_CMD_READ0, 0),
		NAND_OP_ADDR(4, addrs, 0),
		NAND_OP_CMD(NAND_CMD_READSTART, PSEC_TO_NSEC(sdr->tWB_max)),
		NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tR_max),
				 PSEC_TO_NSEC(sdr->tRR_min)),
		NAND_OP_DATA_IN(len, buf, 0),
	};
	struct nand_operation op = NAND_OPERATION(instrs);
	int ret;

	/* Drop the DATA_IN instruction if len is set to 0. */
	if (!len)
		op.ninstrs--;

	ret = nand_fill_column_cycles(chip, addrs, offset_in_page);
	if (ret < 0)
		return ret;

	addrs[2] = page;
	addrs[3] = page >> 8;

	if (chip->options & NAND_ROW_ADDR_3) {
		addrs[4] = page >> 16;
		instrs[1].ctx.addr.naddrs++;
	}

	return nand_exec_op(chip, &op);
}

/**
 * nand_read_page_op - Do a READ PAGE operation
 * @chip: The NAND chip
 * @page: page to read
 * @offset_in_page: offset within the page
 * @buf: buffer used to store the data
 * @len: length of the buffer
 *
 * This function issues a READ PAGE operation.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_read_page_op(struct nand_chip *chip, unsigned int page,
		      unsigned int offset_in_page, void *buf, unsigned int len)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (len && !buf)
		return -EINVAL;

	if (offset_in_page + len > mtd->writesize + mtd->oobsize)
		return -EINVAL;

	if (chip->exec_op) {
		if (mtd->writesize > 512)
			return nand_lp_exec_read_page_op(chip, page,
							 offset_in_page, buf,
							 len);

		return nand_sp_exec_read_page_op(chip, page, offset_in_page,
						 buf, len);
	}

	chip->cmdfunc(mtd, NAND_CMD_READ0, offset_in_page, page);
	if (len)
		chip->read_buf(mtd, buf, len);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_read_page_op);

/**
 * nand_read_param_page_op - Do a READ PARAMETER PAGE operation
 * @chip: The NAND chip
 * @page: parameter page to read
 * @buf: buffer used to store the data
 * @len: length of the buffer
 *
 * This function issues a READ PARAMETER PAGE operation.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
static int nand_read_param_page_op(struct nand_chip *chip, u8 page, void *buf,
				   unsigned int len)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	unsigned int i;
	u8 *p = buf;

	if (len && !buf)
		return -EINVAL;

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_PARAM, 0),
			NAND_OP_ADDR(1, &page, PSEC_TO_NSEC(sdr->tWB_max)),
			NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tR_max),
					 PSEC_TO_NSEC(sdr->tRR_min)),
			NAND_OP_8BIT_DATA_IN(len, buf, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		/* Drop the DATA_IN instruction if len is set to 0. */
		if (!len)
			op.ninstrs--;

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_PARAM, page, -1);
	for (i = 0; i < len; i++)
		p[i] = chip->read_byte(mtd);

	return 0;
}

/**
 * nand_change_read_column_op - Do a CHANGE READ COLUMN operation
 * @chip: The NAND chip
 * @offset_in_page: offset within the page
 * @buf: buffer used to store the data
 * @len: length of the buffer
 * @force_8bit: force 8-bit bus access
 *
 * This function issues a CHANGE READ COLUMN operation.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_change_read_column_op(struct nand_chip *chip,
			       unsigned int offset_in_page, void *buf,
			       unsigned int len, bool force_8bit)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (len && !buf)
		return -EINVAL;

	if (offset_in_page + len > mtd->writesize + mtd->oobsize)
		return -EINVAL;

	/* Small page NANDs do not support column change. */
	if (mtd->writesize <= 512)
		return -ENOTSUPP;

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		u8 addrs[2] = {};
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_RNDOUT, 0),
			NAND_OP_ADDR(2, addrs, 0),
			NAND_OP_CMD(NAND_CMD_RNDOUTSTART,
				    PSEC_TO_NSEC(sdr->tCCS_min)),
			NAND_OP_DATA_IN(len, buf, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);
		int ret;

		ret = nand_fill_column_cycles(chip, addrs, offset_in_page);
		if (ret < 0)
			return ret;

		/* Drop the DATA_IN instruction if len is set to 0. */
		if (!len)
			op.ninstrs--;

		instrs[3].ctx.data.force_8bit = force_8bit;

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_RNDOUT, offset_in_page, -1);
	if (len)
		chip->read_buf(mtd, buf, len);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_change_read_column_op);

/**
 * nand_read_oob_op - Do a READ OOB operation
 * @chip: The NAND chip
 * @page: page to read
 * @offset_in_oob: offset within the OOB area
 * @buf: buffer used to store the data
 * @len: length of the buffer
 *
 * This function issues a READ OOB operation.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_read_oob_op(struct nand_chip *chip, unsigned int page,
		     unsigned int offset_in_oob, void *buf, unsigned int len)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (len && !buf)
		return -EINVAL;

	if (offset_in_oob + len > mtd->oobsize)
		return -EINVAL;

	if (chip->exec_op)
		return nand_read_page_op(chip, page,
					 mtd->writesize + offset_in_oob,
					 buf, len);

	chip->cmdfunc(mtd, NAND_CMD_READOOB, offset_in_oob, page);
	if (len)
		chip->read_buf(mtd, buf, len);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_read_oob_op);

static int nand_exec_prog_page_op(struct nand_chip *chip, unsigned int page,
				  unsigned int offset_in_page, const void *buf,
				  unsigned int len, bool prog)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	const struct nand_sdr_timings *sdr =
		nand_get_sdr_timings(&chip->data_interface);
	u8 addrs[5] = {};
	struct nand_op_instr instrs[] = {
		/*
		 * The first instruction will be dropped if we're dealing
		 * with a large page NAND and adjusted if we're dealing
		 * with a small page NAND and the page offset is > 255.
		 */
		NAND_OP_CMD(NAND_CMD_READ0, 0),
		NAND_OP_CMD(NAND_CMD_SEQIN, 0),
		NAND_OP_ADDR(0, addrs, PSEC_TO_NSEC(sdr->tADL_min)),
		NAND_OP_DATA_OUT(len, buf, 0),
		NAND_OP_CMD(NAND_CMD_PAGEPROG, PSEC_TO_NSEC(sdr->tWB_max)),
		NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tPROG_max), 0),
	};
	struct nand_operation op = NAND_OPERATION(instrs);
	int naddrs = nand_fill_column_cycles(chip, addrs, offset_in_page);
	int ret;
	u8 status;

	if (naddrs < 0)
		return naddrs;

	addrs[naddrs++] = page;
	addrs[naddrs++] = page >> 8;
	if (chip->options & NAND_ROW_ADDR_3)
		addrs[naddrs++] = page >> 16;

	instrs[2].ctx.addr.naddrs = naddrs;

	/* Drop the last two instructions if we're not programming the page. */
	if (!prog) {
		op.ninstrs -= 2;
		/* Also drop the DATA_OUT instruction if empty. */
		if (!len)
			op.ninstrs--;
	}

	if (mtd->writesize <= 512) {
		/*
		 * Small pages need some more tweaking: we have to adjust the
		 * first instruction depending on the page offset we're trying
		 * to access.
		 */
		if (offset_in_page >= mtd->writesize)
			instrs[0].ctx.cmd.opcode = NAND_CMD_READOOB;
		else if (offset_in_page >= 256 &&
			 !(chip->options & NAND_BUSWIDTH_16))
			instrs[0].ctx.cmd.opcode = NAND_CMD_READ1;
	} else {
		/*
		 * Drop the first command if we're dealing with a large page
		 * NAND.
		 */
		op.instrs++;
		op.ninstrs--;
	}

	ret = nand_exec_op(chip, &op);
	if (!prog || ret)
		return ret;

	ret = nand_status_op(chip, &status);
	if (ret)
		return ret;

	return status;
}

/**
 * nand_prog_page_begin_op - starts a PROG PAGE operation
 * @chip: The NAND chip
 * @page: page to write
 * @offset_in_page: offset within the page
 * @buf: buffer containing the data to write to the page
 * @len: length of the buffer
 *
 * This function issues the first half of a PROG PAGE operation.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_prog_page_begin_op(struct nand_chip *chip, unsigned int page,
			    unsigned int offset_in_page, const void *buf,
			    unsigned int len)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (len && !buf)
		return -EINVAL;

	if (offset_in_page + len > mtd->writesize + mtd->oobsize)
		return -EINVAL;

	if (chip->exec_op)
		return nand_exec_prog_page_op(chip, page, offset_in_page, buf,
					      len, false);

	chip->cmdfunc(mtd, NAND_CMD_SEQIN, offset_in_page, page);

	if (buf)
		chip->write_buf(mtd, buf, len);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_prog_page_begin_op);

/**
 * nand_prog_page_end_op - ends a PROG PAGE operation
 * @chip: The NAND chip
 *
 * This function issues the second half of a PROG PAGE operation.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_prog_page_end_op(struct nand_chip *chip)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	int ret;
	u8 status;

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_PAGEPROG,
				    PSEC_TO_NSEC(sdr->tWB_max)),
			NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tPROG_max), 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		ret = nand_exec_op(chip, &op);
		if (ret)
			return ret;

		ret = nand_status_op(chip, &status);
		if (ret)
			return ret;
	} else {
		chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
		ret = chip->waitfunc(mtd, chip);
		if (ret < 0)
			return ret;

		status = ret;
	}

	if (status & NAND_STATUS_FAIL)
		return -EIO;

	return 0;
}
EXPORT_SYMBOL_GPL(nand_prog_page_end_op);

/**
 * nand_prog_page_op - Do a full PROG PAGE operation
 * @chip: The NAND chip
 * @page: page to write
 * @offset_in_page: offset within the page
 * @buf: buffer containing the data to write to the page
 * @len: length of the buffer
 *
 * This function issues a full PROG PAGE operation.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_prog_page_op(struct nand_chip *chip, unsigned int page,
		      unsigned int offset_in_page, const void *buf,
		      unsigned int len)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	int status;

	if (!len || !buf)
		return -EINVAL;

	if (offset_in_page + len > mtd->writesize + mtd->oobsize)
		return -EINVAL;

	if (chip->exec_op) {
		status = nand_exec_prog_page_op(chip, page, offset_in_page, buf,
						len, true);
	} else {
		chip->cmdfunc(mtd, NAND_CMD_SEQIN, offset_in_page, page);
		chip->write_buf(mtd, buf, len);
		chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);
		status = chip->waitfunc(mtd, chip);
	}

	if (status & NAND_STATUS_FAIL)
		return -EIO;

	return 0;
}
EXPORT_SYMBOL_GPL(nand_prog_page_op);

/**
 * nand_change_write_column_op - Do a CHANGE WRITE COLUMN operation
 * @chip: The NAND chip
 * @offset_in_page: offset within the page
 * @buf: buffer containing the data to send to the NAND
 * @len: length of the buffer
 * @force_8bit: force 8-bit bus access
 *
 * This function issues a CHANGE WRITE COLUMN operation.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_change_write_column_op(struct nand_chip *chip,
				unsigned int offset_in_page,
				const void *buf, unsigned int len,
				bool force_8bit)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (len && !buf)
		return -EINVAL;

	if (offset_in_page + len > mtd->writesize + mtd->oobsize)
		return -EINVAL;

	/* Small page NANDs do not support column change. */
	if (mtd->writesize <= 512)
		return -ENOTSUPP;

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		u8 addrs[2];
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_RNDIN, 0),
			NAND_OP_ADDR(2, addrs, PSEC_TO_NSEC(sdr->tCCS_min)),
			NAND_OP_DATA_OUT(len, buf, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);
		int ret;

		ret = nand_fill_column_cycles(chip, addrs, offset_in_page);
		if (ret < 0)
			return ret;

		instrs[2].ctx.data.force_8bit = force_8bit;

		/* Drop the DATA_OUT instruction if len is set to 0. */
		if (!len)
			op.ninstrs--;

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_RNDIN, offset_in_page, -1);
	if (len)
		chip->write_buf(mtd, buf, len);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_change_write_column_op);

/**
 * nand_readid_op - Do a READID operation
 * @chip: The NAND chip
 * @addr: address cycle to pass after the READID command
 * @buf: buffer used to store the ID
 * @len: length of the buffer
 *
 * This function sends a READID command and reads back the ID returned by the
 * NAND.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_readid_op(struct nand_chip *chip, u8 addr, void *buf,
		   unsigned int len)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	unsigned int i;
	u8 *id = buf;

	if (len && !buf)
		return -EINVAL;

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_READID, 0),
			NAND_OP_ADDR(1, &addr, PSEC_TO_NSEC(sdr->tADL_min)),
			NAND_OP_8BIT_DATA_IN(len, buf, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		/* Drop the DATA_IN instruction if len is set to 0. */
		if (!len)
			op.ninstrs--;

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_READID, addr, -1);

	for (i = 0; i < len; i++)
		id[i] = chip->read_byte(mtd);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_readid_op);

/**
 * nand_status_op - Do a STATUS operation
 * @chip: The NAND chip
 * @status: out variable to store the NAND status
 *
 * This function sends a STATUS command and reads back the status returned by
 * the NAND.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_status_op(struct nand_chip *chip, u8 *status)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_STATUS,
				    PSEC_TO_NSEC(sdr->tADL_min)),
			NAND_OP_8BIT_DATA_IN(1, status, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		if (!status)
			op.ninstrs--;

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);
	if (status)
		*status = chip->read_byte(mtd);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_status_op);

/**
 * nand_exit_status_op - Exit a STATUS operation
 * @chip: The NAND chip
 *
 * This function sends a READ0 command to cancel the effect of the STATUS
 * command to avoid reading only the status until a new read command is sent.
 *
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_exit_status_op(struct nand_chip *chip)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (chip->exec_op) {
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_READ0, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_READ0, -1, -1);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_exit_status_op);

/**
 * nand_erase_op - Do an erase operation
 * @chip: The NAND chip
 * @eraseblock: block to erase
 *
 * This function sends an ERASE command and waits for the NAND to be ready
 * before returning.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_erase_op(struct nand_chip *chip, unsigned int eraseblock)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	unsigned int page = eraseblock <<
			    (chip->phys_erase_shift - chip->page_shift);
	int ret;
	u8 status;

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		u8 addrs[3] = {	page, page >> 8, page >> 16 };
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_ERASE1, 0),
			NAND_OP_ADDR(2, addrs, 0),
			NAND_OP_CMD(NAND_CMD_ERASE2,
				    PSEC_TO_MSEC(sdr->tWB_max)),
			NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tBERS_max), 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		if (chip->options & NAND_ROW_ADDR_3)
			instrs[1].ctx.addr.naddrs++;

		ret = nand_exec_op(chip, &op);
		if (ret)
			return ret;

		ret = nand_status_op(chip, &status);
		if (ret)
			return ret;
	} else {
		chip->cmdfunc(mtd, NAND_CMD_ERASE1, -1, page);
		chip->cmdfunc(mtd, NAND_CMD_ERASE2, -1, -1);

		ret = chip->waitfunc(mtd, chip);
		if (ret < 0)
			return ret;

		status = ret;
	}

	if (status & NAND_STATUS_FAIL)
		return -EIO;

	return 0;
}
EXPORT_SYMBOL_GPL(nand_erase_op);

/**
 * nand_set_features_op - Do a SET FEATURES operation
 * @chip: The NAND chip
 * @feature: feature id
 * @data: 4 bytes of data
 *
 * This function sends a SET FEATURES command and waits for the NAND to be
 * ready before returning.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
static int nand_set_features_op(struct nand_chip *chip, u8 feature,
				const void *data)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	const u8 *params = data;
	int i, ret;

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_SET_FEATURES, 0),
			NAND_OP_ADDR(1, &feature, PSEC_TO_NSEC(sdr->tADL_min)),
			NAND_OP_8BIT_DATA_OUT(ONFI_SUBFEATURE_PARAM_LEN, data,
					      PSEC_TO_NSEC(sdr->tWB_max)),
			NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tFEAT_max), 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_SET_FEATURES, feature, -1);
	for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
		chip->write_byte(mtd, params[i]);

	ret = chip->waitfunc(mtd, chip);
	if (ret < 0)
		return ret;

	if (ret & NAND_STATUS_FAIL)
		return -EIO;

	return 0;
}

/**
 * nand_get_features_op - Do a GET FEATURES operation
 * @chip: The NAND chip
 * @feature: feature id
 * @data: 4 bytes of data
 *
 * This function sends a GET FEATURES command and waits for the NAND to be
 * ready before returning.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
static int nand_get_features_op(struct nand_chip *chip, u8 feature,
				void *data)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	u8 *params = data;
	int i;

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_GET_FEATURES, 0),
			NAND_OP_ADDR(1, &feature, PSEC_TO_NSEC(sdr->tWB_max)),
			NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tFEAT_max),
					 PSEC_TO_NSEC(sdr->tRR_min)),
			NAND_OP_8BIT_DATA_IN(ONFI_SUBFEATURE_PARAM_LEN,
					     data, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_GET_FEATURES, feature, -1);
	for (i = 0; i < ONFI_SUBFEATURE_PARAM_LEN; ++i)
		params[i] = chip->read_byte(mtd);

	return 0;
}

/**
 * nand_reset_op - Do a reset operation
 * @chip: The NAND chip
 *
 * This function sends a RESET command and waits for the NAND to be ready
 * before returning.
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_reset_op(struct nand_chip *chip)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (chip->exec_op) {
		const struct nand_sdr_timings *sdr =
			nand_get_sdr_timings(&chip->data_interface);
		struct nand_op_instr instrs[] = {
			NAND_OP_CMD(NAND_CMD_RESET, PSEC_TO_NSEC(sdr->tWB_max)),
			NAND_OP_WAIT_RDY(PSEC_TO_MSEC(sdr->tRST_max), 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		return nand_exec_op(chip, &op);
	}

	chip->cmdfunc(mtd, NAND_CMD_RESET, -1, -1);

	return 0;
}
EXPORT_SYMBOL_GPL(nand_reset_op);

/**
 * nand_read_data_op - Read data from the NAND
 * @chip: The NAND chip
 * @buf: buffer used to store the data
 * @len: length of the buffer
 * @force_8bit: force 8-bit bus access
 *
 * This function does a raw data read on the bus. Usually used after launching
 * another NAND operation like nand_read_page_op().
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_read_data_op(struct nand_chip *chip, void *buf, unsigned int len,
		      bool force_8bit)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (!len || !buf)
		return -EINVAL;

	if (chip->exec_op) {
		struct nand_op_instr instrs[] = {
			NAND_OP_DATA_IN(len, buf, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		instrs[0].ctx.data.force_8bit = force_8bit;

		return nand_exec_op(chip, &op);
	}

	if (force_8bit) {
		u8 *p = buf;
		unsigned int i;

		for (i = 0; i < len; i++)
			p[i] = chip->read_byte(mtd);
	} else {
		chip->read_buf(mtd, buf, len);
	}

	return 0;
}
EXPORT_SYMBOL_GPL(nand_read_data_op);

/**
 * nand_write_data_op - Write data from the NAND
 * @chip: The NAND chip
 * @buf: buffer containing the data to send on the bus
 * @len: length of the buffer
 * @force_8bit: force 8-bit bus access
 *
 * This function does a raw data write on the bus. Usually used after launching
 * another NAND operation like nand_write_page_begin_op().
 * This function does not select/unselect the CS line.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_write_data_op(struct nand_chip *chip, const void *buf,
		       unsigned int len, bool force_8bit)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (!len || !buf)
		return -EINVAL;

	if (chip->exec_op) {
		struct nand_op_instr instrs[] = {
			NAND_OP_DATA_OUT(len, buf, 0),
		};
		struct nand_operation op = NAND_OPERATION(instrs);

		instrs[0].ctx.data.force_8bit = force_8bit;

		return nand_exec_op(chip, &op);
	}

	if (force_8bit) {
		const u8 *p = buf;
		unsigned int i;

		for (i = 0; i < len; i++)
			chip->write_byte(mtd, p[i]);
	} else {
		chip->write_buf(mtd, buf, len);
	}

	return 0;
}
EXPORT_SYMBOL_GPL(nand_write_data_op);

/**
 * struct nand_op_parser_ctx - Context used by the parser
 * @instrs: array of all the instructions that must be addressed
 * @ninstrs: length of the @instrs array
 * @subop: Sub-operation to be passed to the NAND controller
 *
 * This structure is used by the core to split NAND operations into
 * sub-operations that can be handled by the NAND controller.
 */
struct nand_op_parser_ctx {
	const struct nand_op_instr *instrs;
	unsigned int ninstrs;
	struct nand_subop subop;
};

/**
 * nand_op_parser_must_split_instr - Checks if an instruction must be split
 * @pat: the parser pattern element that matches @instr
 * @instr: pointer to the instruction to check
 * @start_offset: this is an in/out parameter. If @instr has already been
 *		  split, then @start_offset is the offset from which to start
 *		  (either an address cycle or an offset in the data buffer).
 *		  Conversely, if the function returns true (ie. instr must be
 *		  split), this parameter is updated to point to the first
 *		  data/address cycle that has not been taken care of.
 *
 * Some NAND controllers are limited and cannot send X address cycles with a
 * unique operation, or cannot read/write more than Y bytes at the same time.
 * In this case, split the instruction that does not fit in a single
 * controller-operation into two or more chunks.
 *
 * Returns true if the instruction must be split, false otherwise.
 * The @start_offset parameter is also updated to the offset at which the next
 * bundle of instruction must start (if an address or a data instruction).
 */
static bool
nand_op_parser_must_split_instr(const struct nand_op_parser_pattern_elem *pat,
				const struct nand_op_instr *instr,
				unsigned int *start_offset)
{
	switch (pat->type) {
	case NAND_OP_ADDR_INSTR:
		if (!pat->ctx.addr.maxcycles)
			break;

		if (instr->ctx.addr.naddrs - *start_offset >
		    pat->ctx.addr.maxcycles) {
			*start_offset += pat->ctx.addr.maxcycles;
			return true;
		}
		break;

	case NAND_OP_DATA_IN_INSTR:
	case NAND_OP_DATA_OUT_INSTR:
		if (!pat->ctx.data.maxlen)
			break;

		if (instr->ctx.data.len - *start_offset >
		    pat->ctx.data.maxlen) {
			*start_offset += pat->ctx.data.maxlen;
			return true;
		}
		break;

	default:
		break;
	}

	return false;
}

/**
 * nand_op_parser_match_pat - Checks if a pattern matches the instructions
 *			      remaining in the parser context
 * @pat: the pattern to test
 * @ctx: the parser context structure to match with the pattern @pat
 *
 * Check if @pat matches the set or a sub-set of instructions remaining in @ctx.
 * Returns true if this is the case, false ortherwise. When true is returned,
 * @ctx->subop is updated with the set of instructions to be passed to the
 * controller driver.
 */
static bool
nand_op_parser_match_pat(const struct nand_op_parser_pattern *pat,
			 struct nand_op_parser_ctx *ctx)
{
	unsigned int instr_offset = ctx->subop.first_instr_start_off;
	const struct nand_op_instr *end = ctx->instrs + ctx->ninstrs;
	const struct nand_op_instr *instr = ctx->subop.instrs;
	unsigned int i, ninstrs;

	for (i = 0, ninstrs = 0; i < pat->nelems && instr < end; i++) {
		/*
		 * The pattern instruction does not match the operation
		 * instruction. If the instruction is marked optional in the
		 * pattern definition, we skip the pattern element and continue
		 * to the next one. If the element is mandatory, there's no
		 * match and we can return false directly.
		 */
		if (instr->type != pat->elems[i].type) {
			if (!pat->elems[i].optional)
				return false;

			continue;
		}

		/*
		 * Now check the pattern element constraints. If the pattern is
		 * not able to handle the whole instruction in a single step,
		 * we have to split it.
		 * The last_instr_end_off value comes back updated to point to
		 * the position where we have to split the instruction (the
		 * start of the next subop chunk).
		 */
		if (nand_op_parser_must_split_instr(&pat->elems[i], instr,
						    &instr_offset)) {
			ninstrs++;
			i++;
			break;
		}

		instr++;
		ninstrs++;
		instr_offset = 0;
	}

	/*
	 * This can happen if all instructions of a pattern are optional.
	 * Still, if there's not at least one instruction handled by this
	 * pattern, this is not a match, and we should try the next one (if
	 * any).
	 */
	if (!ninstrs)
		return false;

	/*
	 * We had a match on the pattern head, but the pattern may be longer
	 * than the instructions we're asked to execute. We need to make sure
	 * there's no mandatory elements in the pattern tail.
	 */
	for (; i < pat->nelems; i++) {
		if (!pat->elems[i].optional)
			return false;
	}

	/*
	 * We have a match: update the subop structure accordingly and return
	 * true.
	 */
	ctx->subop.ninstrs = ninstrs;
	ctx->subop.last_instr_end_off = instr_offset;

	return true;
}

#if IS_ENABLED(CONFIG_DYNAMIC_DEBUG) || defined(DEBUG)
static void nand_op_parser_trace(const struct nand_op_parser_ctx *ctx)
{
	const struct nand_op_instr *instr;
	char *prefix = "      ";
	unsigned int i;

	pr_debug("executing subop:\n");

	for (i = 0; i < ctx->ninstrs; i++) {
		instr = &ctx->instrs[i];

		if (instr == &ctx->subop.instrs[0])
			prefix = "    ->";

		switch (instr->type) {
		case NAND_OP_CMD_INSTR:
			pr_debug("%sCMD      [0x%02x]\n", prefix,
				 instr->ctx.cmd.opcode);
			break;
		case NAND_OP_ADDR_INSTR:
			pr_debug("%sADDR     [%d cyc: %*ph]\n", prefix,
				 instr->ctx.addr.naddrs,
				 instr->ctx.addr.naddrs < 64 ?
				 instr->ctx.addr.naddrs : 64,
				 instr->ctx.addr.addrs);
			break;
		case NAND_OP_DATA_IN_INSTR:
			pr_debug("%sDATA_IN  [%d B%s]\n", prefix,
				 instr->ctx.data.len,
				 instr->ctx.data.force_8bit ?
				 ", force 8-bit" : "");
			break;
		case NAND_OP_DATA_OUT_INSTR:
			pr_debug("%sDATA_OUT [%d B%s]\n", prefix,
				 instr->ctx.data.len,
				 instr->ctx.data.force_8bit ?
				 ", force 8-bit" : "");
			break;
		case NAND_OP_WAITRDY_INSTR:
			pr_debug("%sWAITRDY  [max %d ms]\n", prefix,
				 instr->ctx.waitrdy.timeout_ms);
			break;
		}

		if (instr == &ctx->subop.instrs[ctx->subop.ninstrs - 1])
			prefix = "      ";
	}
}
#else
static void nand_op_parser_trace(const struct nand_op_parser_ctx *ctx)
{
	/* NOP */
}
#endif

/**
 * nand_op_parser_exec_op - exec_op parser
 * @chip: the NAND chip
 * @parser: patterns description provided by the controller driver
 * @op: the NAND operation to address
 * @check_only: when true, the function only checks if @op can be handled but
 *		does not execute the operation
 *
 * Helper function designed to ease integration of NAND controller drivers that
 * only support a limited set of instruction sequences. The supported sequences
 * are described in @parser, and the framework takes care of splitting @op into
 * multiple sub-operations (if required) and pass them back to the ->exec()
 * callback of the matching pattern if @check_only is set to false.
 *
 * NAND controller drivers should call this function from their own ->exec_op()
 * implementation.
 *
 * Returns 0 on success, a negative error code otherwise. A failure can be
 * caused by an unsupported operation (none of the supported patterns is able
 * to handle the requested operation), or an error returned by one of the
 * matching pattern->exec() hook.
 */
int nand_op_parser_exec_op(struct nand_chip *chip,
			   const struct nand_op_parser *parser,
			   const struct nand_operation *op, bool check_only)
{
	struct nand_op_parser_ctx ctx = {
		.subop.instrs = op->instrs,
		.instrs = op->instrs,
		.ninstrs = op->ninstrs,
	};
	unsigned int i;

	while (ctx.subop.instrs < op->instrs + op->ninstrs) {
		int ret;

		for (i = 0; i < parser->npatterns; i++) {
			const struct nand_op_parser_pattern *pattern;

			pattern = &parser->patterns[i];
			if (!nand_op_parser_match_pat(pattern, &ctx))
				continue;

			nand_op_parser_trace(&ctx);

			if (check_only)
				break;

			ret = pattern->exec(chip, &ctx.subop);
			if (ret)
				return ret;

			break;
		}

		if (i == parser->npatterns) {
			pr_debug("->exec_op() parser: pattern not found!\n");
			return -ENOTSUPP;
		}

		/*
		 * Update the context structure by pointing to the start of the
		 * next subop.
		 */
		ctx.subop.instrs = ctx.subop.instrs + ctx.subop.ninstrs;
		if (ctx.subop.last_instr_end_off)
			ctx.subop.instrs -= 1;

		ctx.subop.first_instr_start_off = ctx.subop.last_instr_end_off;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(nand_op_parser_exec_op);

static bool nand_instr_is_data(const struct nand_op_instr *instr)
{
	return instr && (instr->type == NAND_OP_DATA_IN_INSTR ||
			 instr->type == NAND_OP_DATA_OUT_INSTR);
}

static bool nand_subop_instr_is_valid(const struct nand_subop *subop,
				      unsigned int instr_idx)
{
	return subop && instr_idx < subop->ninstrs;
}

static unsigned int nand_subop_get_start_off(const struct nand_subop *subop,
					     unsigned int instr_idx)
{
	if (instr_idx)
		return 0;

	return subop->first_instr_start_off;
}

/**
 * nand_subop_get_addr_start_off - Get the start offset in an address array
 * @subop: The entire sub-operation
 * @instr_idx: Index of the instruction inside the sub-operation
 *
 * During driver development, one could be tempted to directly use the
 * ->addr.addrs field of address instructions. This is wrong as address
 * instructions might be split.
 *
 * Given an address instruction, returns the offset of the first cycle to issue.
 */
unsigned int nand_subop_get_addr_start_off(const struct nand_subop *subop,
					   unsigned int instr_idx)
{
	if (WARN_ON(!nand_subop_instr_is_valid(subop, instr_idx) ||
		    subop->instrs[instr_idx].type != NAND_OP_ADDR_INSTR))
		return 0;

	return nand_subop_get_start_off(subop, instr_idx);
}
EXPORT_SYMBOL_GPL(nand_subop_get_addr_start_off);

/**
 * nand_subop_get_num_addr_cyc - Get the remaining address cycles to assert
 * @subop: The entire sub-operation
 * @instr_idx: Index of the instruction inside the sub-operation
 *
 * During driver development, one could be tempted to directly use the
 * ->addr->naddrs field of a data instruction. This is wrong as instructions
 * might be split.
 *
 * Given an address instruction, returns the number of address cycle to issue.
 */
unsigned int nand_subop_get_num_addr_cyc(const struct nand_subop *subop,
					 unsigned int instr_idx)
{
	int start_off, end_off;

	if (WARN_ON(!nand_subop_instr_is_valid(subop, instr_idx) ||
		    subop->instrs[instr_idx].type != NAND_OP_ADDR_INSTR))
		return 0;

	start_off = nand_subop_get_addr_start_off(subop, instr_idx);

	if (instr_idx == subop->ninstrs - 1 &&
	    subop->last_instr_end_off)
		end_off = subop->last_instr_end_off;
	else
		end_off = subop->instrs[instr_idx].ctx.addr.naddrs;

	return end_off - start_off;
}
EXPORT_SYMBOL_GPL(nand_subop_get_num_addr_cyc);

/**
 * nand_subop_get_data_start_off - Get the start offset in a data array
 * @subop: The entire sub-operation
 * @instr_idx: Index of the instruction inside the sub-operation
 *
 * During driver development, one could be tempted to directly use the
 * ->data->buf.{in,out} field of data instructions. This is wrong as data
 * instructions might be split.
 *
 * Given a data instruction, returns the offset to start from.
 */
unsigned int nand_subop_get_data_start_off(const struct nand_subop *subop,
					   unsigned int instr_idx)
{
	if (WARN_ON(!nand_subop_instr_is_valid(subop, instr_idx) ||
		    !nand_instr_is_data(&subop->instrs[instr_idx])))
		return 0;

	return nand_subop_get_start_off(subop, instr_idx);
}
EXPORT_SYMBOL_GPL(nand_subop_get_data_start_off);

/**
 * nand_subop_get_data_len - Get the number of bytes to retrieve
 * @subop: The entire sub-operation
 * @instr_idx: Index of the instruction inside the sub-operation
 *
 * During driver development, one could be tempted to directly use the
 * ->data->len field of a data instruction. This is wrong as data instructions
 * might be split.
 *
 * Returns the length of the chunk of data to send/receive.
 */
unsigned int nand_subop_get_data_len(const struct nand_subop *subop,
				     unsigned int instr_idx)
{
	int start_off = 0, end_off;

	if (WARN_ON(!nand_subop_instr_is_valid(subop, instr_idx) ||
		    !nand_instr_is_data(&subop->instrs[instr_idx])))
		return 0;

	start_off = nand_subop_get_data_start_off(subop, instr_idx);

	if (instr_idx == subop->ninstrs - 1 &&
	    subop->last_instr_end_off)
		end_off = subop->last_instr_end_off;
	else
		end_off = subop->instrs[instr_idx].ctx.data.len;

	return end_off - start_off;
}
EXPORT_SYMBOL_GPL(nand_subop_get_data_len);

/**
 * nand_reset - Reset and initialize a NAND device
 * @chip: The NAND chip
 * @chipnr: Internal die id
 *
 * Save the timings data structure, then apply SDR timings mode 0 (see
 * nand_reset_data_interface for details), do the reset operation, and
 * apply back the previous timings.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int nand_reset(struct nand_chip *chip, int chipnr)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	struct nand_data_interface saved_data_intf = chip->data_interface;
	int ret;

	ret = nand_reset_data_interface(chip, chipnr);
	if (ret)
		return ret;

	/*
	 * The CS line has to be released before we can apply the new NAND
	 * interface settings, hence this weird ->select_chip() dance.
	 */
	chip->select_chip(mtd, chipnr);
	ret = nand_reset_op(chip);
	chip->select_chip(mtd, -1);
	if (ret)
		return ret;

	/*
	 * A nand_reset_data_interface() put both the NAND chip and the NAND
	 * controller in timings mode 0. If the default mode for this chip is
	 * also 0, no need to proceed to the change again. Plus, at probe time,
	 * nand_setup_data_interface() uses ->set/get_features() which would
	 * fail anyway as the parameter page is not available yet.
	 */
	if (!chip->onfi_timing_mode_default)
		return 0;

	chip->data_interface = saved_data_intf;
	ret = nand_setup_data_interface(chip, chipnr);
	if (ret)
		return ret;

	return 0;
}
EXPORT_SYMBOL_GPL(nand_reset);

/**
 * nand_check_erased_buf - check if a buffer contains (almost) only 0xff data
 * @buf: buffer to test
 * @len: buffer length
 * @bitflips_threshold: maximum number of bitflips
 *
 * Check if a buffer contains only 0xff, which means the underlying region
 * has been erased and is ready to be programmed.
 * The bitflips_threshold specify the maximum number of bitflips before
 * considering the region is not erased.
 * Note: The logic of this function has been extracted from the memweight
 * implementation, except that nand_check_erased_buf function exit before
 * testing the whole buffer if the number of bitflips exceed the
 * bitflips_threshold value.
 *
 * Returns a positive number of bitflips less than or equal to
 * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the
 * threshold.
 */
static int nand_check_erased_buf(void *buf, int len, int bitflips_threshold)
{
	const unsigned char *bitmap = buf;
	int bitflips = 0;
	int weight;

	for (; len && ((uintptr_t)bitmap) % sizeof(long);
	     len--, bitmap++) {
		weight = hweight8(*bitmap);
		bitflips += BITS_PER_BYTE - weight;
		if (unlikely(bitflips > bitflips_threshold))
			return -EBADMSG;
	}

	for (; len >= sizeof(long);
	     len -= sizeof(long), bitmap += sizeof(long)) {
		unsigned long d = *((unsigned long *)bitmap);
		if (d == ~0UL)
			continue;
		weight = hweight_long(d);
		bitflips += BITS_PER_LONG - weight;
		if (unlikely(bitflips > bitflips_threshold))
			return -EBADMSG;
	}

	for (; len > 0; len--, bitmap++) {
		weight = hweight8(*bitmap);
		bitflips += BITS_PER_BYTE - weight;
		if (unlikely(bitflips > bitflips_threshold))
			return -EBADMSG;
	}

	return bitflips;
}

/**
 * nand_check_erased_ecc_chunk - check if an ECC chunk contains (almost) only
 *				 0xff data
 * @data: data buffer to test
 * @datalen: data length
 * @ecc: ECC buffer
 * @ecclen: ECC length
 * @extraoob: extra OOB buffer
 * @extraooblen: extra OOB length
 * @bitflips_threshold: maximum number of bitflips
 *
 * Check if a data buffer and its associated ECC and OOB data contains only
 * 0xff pattern, which means the underlying region has been erased and is
 * ready to be programmed.
 * The bitflips_threshold specify the maximum number of bitflips before
 * considering the region as not erased.
 *
 * Note:
 * 1/ ECC algorithms are working on pre-defined block sizes which are usually
 *    different from the NAND page size. When fixing bitflips, ECC engines will
 *    report the number of errors per chunk, and the NAND core infrastructure
 *    expect you to return the maximum number of bitflips for the whole page.
 *    This is why you should always use this function on a single chunk and
 *    not on the whole page. After checking each chunk you should update your
 *    max_bitflips value accordingly.
 * 2/ When checking for bitflips in erased pages you should not only check
 *    the payload data but also their associated ECC data, because a user might
 *    have programmed almost all bits to 1 but a few. In this case, we
 *    shouldn't consider the chunk as erased, and checking ECC bytes prevent
 *    this case.
 * 3/ The extraoob argument is optional, and should be used if some of your OOB
 *    data are protected by the ECC engine.
 *    It could also be used if you support subpages and want to attach some
 *    extra OOB data to an ECC chunk.
 *
 * Returns a positive number of bitflips less than or equal to
 * bitflips_threshold, or -ERROR_CODE for bitflips in excess of the
 * threshold. In case of success, the passed buffers are filled with 0xff.
 */
int nand_check_erased_ecc_chunk(void *data, int datalen,
				void *ecc, int ecclen,
				void *extraoob, int extraooblen,
				int bitflips_threshold)
{
	int data_bitflips = 0, ecc_bitflips = 0, extraoob_bitflips = 0;

	data_bitflips = nand_check_erased_buf(data, datalen,
					      bitflips_threshold);
	if (data_bitflips < 0)
		return data_bitflips;

	bitflips_threshold -= data_bitflips;

	ecc_bitflips = nand_check_erased_buf(ecc, ecclen, bitflips_threshold);
	if (ecc_bitflips < 0)
		return ecc_bitflips;

	bitflips_threshold -= ecc_bitflips;

	extraoob_bitflips = nand_check_erased_buf(extraoob, extraooblen,
						  bitflips_threshold);
	if (extraoob_bitflips < 0)
		return extraoob_bitflips;

	if (data_bitflips)
		memset(data, 0xff, datalen);

	if (ecc_bitflips)
		memset(ecc, 0xff, ecclen);

	if (extraoob_bitflips)
		memset(extraoob, 0xff, extraooblen);

	return data_bitflips + ecc_bitflips + extraoob_bitflips;
}
EXPORT_SYMBOL(nand_check_erased_ecc_chunk);

/**
 * nand_read_page_raw_notsupp - dummy read raw page function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Returns -ENOTSUPP unconditionally.
 */
int nand_read_page_raw_notsupp(struct mtd_info *mtd, struct nand_chip *chip,
			       u8 *buf, int oob_required, int page)
{
	return -ENOTSUPP;
}
EXPORT_SYMBOL(nand_read_page_raw_notsupp);

/**
 * nand_read_page_raw - [INTERN] read raw page data without ecc
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Not for syndrome calculating ECC controllers, which use a special oob layout.
 */
int nand_read_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
		       uint8_t *buf, int oob_required, int page)
{
	int ret;

	ret = nand_read_page_op(chip, page, 0, buf, mtd->writesize);
	if (ret)
		return ret;

	if (oob_required) {
		ret = nand_read_data_op(chip, chip->oob_poi, mtd->oobsize,
					false);
		if (ret)
			return ret;
	}

	return 0;
}
EXPORT_SYMBOL(nand_read_page_raw);

/**
 * nand_read_page_raw_syndrome - [INTERN] read raw page data without ecc
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * We need a special oob layout and handling even when OOB isn't used.
 */
static int nand_read_page_raw_syndrome(struct mtd_info *mtd,
				       struct nand_chip *chip, uint8_t *buf,
				       int oob_required, int page)
{
	int eccsize = chip->ecc.size;
	int eccbytes = chip->ecc.bytes;
	uint8_t *oob = chip->oob_poi;
	int steps, size, ret;

	ret = nand_read_page_op(chip, page, 0, NULL, 0);
	if (ret)
		return ret;

	for (steps = chip->ecc.steps; steps > 0; steps--) {
		ret = nand_read_data_op(chip, buf, eccsize, false);
		if (ret)
			return ret;

		buf += eccsize;

		if (chip->ecc.prepad) {
			ret = nand_read_data_op(chip, oob, chip->ecc.prepad,
						false);
			if (ret)
				return ret;

			oob += chip->ecc.prepad;
		}

		ret = nand_read_data_op(chip, oob, eccbytes, false);
		if (ret)
			return ret;

		oob += eccbytes;

		if (chip->ecc.postpad) {
			ret = nand_read_data_op(chip, oob, chip->ecc.postpad,
						false);
			if (ret)
				return ret;

			oob += chip->ecc.postpad;
		}
	}

	size = mtd->oobsize - (oob - chip->oob_poi);
	if (size) {
		ret = nand_read_data_op(chip, oob, size, false);
		if (ret)
			return ret;
	}

	return 0;
}

/**
 * nand_read_page_swecc - [REPLACEABLE] software ECC based page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 */
static int nand_read_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
				uint8_t *buf, int oob_required, int page)
{
	int i, eccsize = chip->ecc.size, ret;
	int eccbytes = chip->ecc.bytes;
	int eccsteps = chip->ecc.steps;
	uint8_t *p = buf;
	uint8_t *ecc_calc = chip->ecc.calc_buf;
	uint8_t *ecc_code = chip->ecc.code_buf;
	unsigned int max_bitflips = 0;

	chip->ecc.read_page_raw(mtd, chip, buf, 1, page);

	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize)
		chip->ecc.calculate(mtd, p, &ecc_calc[i]);

	ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code, chip->oob_poi, 0,
					 chip->ecc.total);
	if (ret)
		return ret;

	eccsteps = chip->ecc.steps;
	p = buf;

	for (i = 0 ; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
		int stat;

		stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
		if (stat < 0) {
			mtd->ecc_stats.failed++;
		} else {
			mtd->ecc_stats.corrected += stat;
			max_bitflips = max_t(unsigned int, max_bitflips, stat);
		}
	}
	return max_bitflips;
}

/**
 * nand_read_subpage - [REPLACEABLE] ECC based sub-page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @data_offs: offset of requested data within the page
 * @readlen: data length
 * @bufpoi: buffer to store read data
 * @page: page number to read
 */
static int nand_read_subpage(struct mtd_info *mtd, struct nand_chip *chip,
			uint32_t data_offs, uint32_t readlen, uint8_t *bufpoi,
			int page)
{
	int start_step, end_step, num_steps, ret;
	uint8_t *p;
	int data_col_addr, i, gaps = 0;
	int datafrag_len, eccfrag_len, aligned_len, aligned_pos;
	int busw = (chip->options & NAND_BUSWIDTH_16) ? 2 : 1;
	int index, section = 0;
	unsigned int max_bitflips = 0;
	struct mtd_oob_region oobregion = { };

	/* Column address within the page aligned to ECC size (256bytes) */
	start_step = data_offs / chip->ecc.size;
	end_step = (data_offs + readlen - 1) / chip->ecc.size;
	num_steps = end_step - start_step + 1;
	index = start_step * chip->ecc.bytes;

	/* Data size aligned to ECC ecc.size */
	datafrag_len = num_steps * chip->ecc.size;
	eccfrag_len = num_steps * chip->ecc.bytes;

	data_col_addr = start_step * chip->ecc.size;
	/* If we read not a page aligned data */
	p = bufpoi + data_col_addr;
	ret = nand_read_page_op(chip, page, data_col_addr, p, datafrag_len);
	if (ret)
		return ret;

	/* Calculate ECC */
	for (i = 0; i < eccfrag_len ; i += chip->ecc.bytes, p += chip->ecc.size)
		chip->ecc.calculate(mtd, p, &chip->ecc.calc_buf[i]);

	/*
	 * The performance is faster if we position offsets according to
	 * ecc.pos. Let's make sure that there are no gaps in ECC positions.
	 */
	ret = mtd_ooblayout_find_eccregion(mtd, index, &section, &oobregion);
	if (ret)
		return ret;

	if (oobregion.length < eccfrag_len)
		gaps = 1;

	if (gaps) {
		ret = nand_change_read_column_op(chip, mtd->writesize,
						 chip->oob_poi, mtd->oobsize,
						 false);
		if (ret)
			return ret;
	} else {
		/*
		 * Send the command to read the particular ECC bytes take care
		 * about buswidth alignment in read_buf.
		 */
		aligned_pos = oobregion.offset & ~(busw - 1);
		aligned_len = eccfrag_len;
		if (oobregion.offset & (busw - 1))
			aligned_len++;
		if ((oobregion.offset + (num_steps * chip->ecc.bytes)) &
		    (busw - 1))
			aligned_len++;

		ret = nand_change_read_column_op(chip,
						 mtd->writesize + aligned_pos,
						 &chip->oob_poi[aligned_pos],
						 aligned_len, false);
		if (ret)
			return ret;
	}

	ret = mtd_ooblayout_get_eccbytes(mtd, chip->ecc.code_buf,
					 chip->oob_poi, index, eccfrag_len);
	if (ret)
		return ret;

	p = bufpoi + data_col_addr;
	for (i = 0; i < eccfrag_len ; i += chip->ecc.bytes, p += chip->ecc.size) {
		int stat;

		stat = chip->ecc.correct(mtd, p, &chip->ecc.code_buf[i],
					 &chip->ecc.calc_buf[i]);
		if (stat == -EBADMSG &&
		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
			/* check for empty pages with bitflips */
			stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
						&chip->ecc.code_buf[i],
						chip->ecc.bytes,
						NULL, 0,
						chip->ecc.strength);
		}

		if (stat < 0) {
			mtd->ecc_stats.failed++;
		} else {
			mtd->ecc_stats.corrected += stat;
			max_bitflips = max_t(unsigned int, max_bitflips, stat);
		}
	}
	return max_bitflips;
}

/**
 * nand_read_page_hwecc - [REPLACEABLE] hardware ECC based page read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Not for syndrome calculating ECC controllers which need a special oob layout.
 */
static int nand_read_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
				uint8_t *buf, int oob_required, int page)
{
	int i, eccsize = chip->ecc.size, ret;
	int eccbytes = chip->ecc.bytes;
	int eccsteps = chip->ecc.steps;
	uint8_t *p = buf;
	uint8_t *ecc_calc = chip->ecc.calc_buf;
	uint8_t *ecc_code = chip->ecc.code_buf;
	unsigned int max_bitflips = 0;

	ret = nand_read_page_op(chip, page, 0, NULL, 0);
	if (ret)
		return ret;

	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
		chip->ecc.hwctl(mtd, NAND_ECC_READ);

		ret = nand_read_data_op(chip, p, eccsize, false);
		if (ret)
			return ret;

		chip->ecc.calculate(mtd, p, &ecc_calc[i]);
	}

	ret = nand_read_data_op(chip, chip->oob_poi, mtd->oobsize, false);
	if (ret)
		return ret;

	ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code, chip->oob_poi, 0,
					 chip->ecc.total);
	if (ret)
		return ret;

	eccsteps = chip->ecc.steps;
	p = buf;

	for (i = 0 ; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
		int stat;

		stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
		if (stat == -EBADMSG &&
		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
			/* check for empty pages with bitflips */
			stat = nand_check_erased_ecc_chunk(p, eccsize,
						&ecc_code[i], eccbytes,
						NULL, 0,
						chip->ecc.strength);
		}

		if (stat < 0) {
			mtd->ecc_stats.failed++;
		} else {
			mtd->ecc_stats.corrected += stat;
			max_bitflips = max_t(unsigned int, max_bitflips, stat);
		}
	}
	return max_bitflips;
}

/**
 * nand_read_page_hwecc_oob_first - [REPLACEABLE] hw ecc, read oob first
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * Hardware ECC for large page chips, require OOB to be read first. For this
 * ECC mode, the write_page method is re-used from ECC_HW. These methods
 * read/write ECC from the OOB area, unlike the ECC_HW_SYNDROME support with
 * multiple ECC steps, follows the "infix ECC" scheme and reads/writes ECC from
 * the data area, by overwriting the NAND manufacturer bad block markings.
 */
static int nand_read_page_hwecc_oob_first(struct mtd_info *mtd,
	struct nand_chip *chip, uint8_t *buf, int oob_required, int page)
{
	int i, eccsize = chip->ecc.size, ret;
	int eccbytes = chip->ecc.bytes;
	int eccsteps = chip->ecc.steps;
	uint8_t *p = buf;
	uint8_t *ecc_code = chip->ecc.code_buf;
	uint8_t *ecc_calc = chip->ecc.calc_buf;
	unsigned int max_bitflips = 0;

	/* Read the OOB area first */
	ret = nand_read_oob_op(chip, page, 0, chip->oob_poi, mtd->oobsize);
	if (ret)
		return ret;

	ret = nand_read_page_op(chip, page, 0, NULL, 0);
	if (ret)
		return ret;

	ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code, chip->oob_poi, 0,
					 chip->ecc.total);
	if (ret)
		return ret;

	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
		int stat;

		chip->ecc.hwctl(mtd, NAND_ECC_READ);

		ret = nand_read_data_op(chip, p, eccsize, false);
		if (ret)
			return ret;

		chip->ecc.calculate(mtd, p, &ecc_calc[i]);

		stat = chip->ecc.correct(mtd, p, &ecc_code[i], NULL);
		if (stat == -EBADMSG &&
		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
			/* check for empty pages with bitflips */
			stat = nand_check_erased_ecc_chunk(p, eccsize,
						&ecc_code[i], eccbytes,
						NULL, 0,
						chip->ecc.strength);
		}

		if (stat < 0) {
			mtd->ecc_stats.failed++;
		} else {
			mtd->ecc_stats.corrected += stat;
			max_bitflips = max_t(unsigned int, max_bitflips, stat);
		}
	}
	return max_bitflips;
}

/**
 * nand_read_page_syndrome - [REPLACEABLE] hardware ECC syndrome based page read
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: buffer to store read data
 * @oob_required: caller requires OOB data read to chip->oob_poi
 * @page: page number to read
 *
 * The hw generator calculates the error syndrome automatically. Therefore we
 * need a special oob layout and handling.
 */
static int nand_read_page_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
				   uint8_t *buf, int oob_required, int page)
{
	int ret, i, eccsize = chip->ecc.size;
	int eccbytes = chip->ecc.bytes;
	int eccsteps = chip->ecc.steps;
	int eccpadbytes = eccbytes + chip->ecc.prepad + chip->ecc.postpad;
	uint8_t *p = buf;
	uint8_t *oob = chip->oob_poi;
	unsigned int max_bitflips = 0;

	ret = nand_read_page_op(chip, page, 0, NULL, 0);
	if (ret)
		return ret;

	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
		int stat;

		chip->ecc.hwctl(mtd, NAND_ECC_READ);

		ret = nand_read_data_op(chip, p, eccsize, false);
		if (ret)
			return ret;

		if (chip->ecc.prepad) {
			ret = nand_read_data_op(chip, oob, chip->ecc.prepad,
						false);
			if (ret)
				return ret;

			oob += chip->ecc.prepad;
		}

		chip->ecc.hwctl(mtd, NAND_ECC_READSYN);

		ret = nand_read_data_op(chip, oob, eccbytes, false);
		if (ret)
			return ret;

		stat = chip->ecc.correct(mtd, p, oob, NULL);

		oob += eccbytes;

		if (chip->ecc.postpad) {
			ret = nand_read_data_op(chip, oob, chip->ecc.postpad,
						false);
			if (ret)
				return ret;

			oob += chip->ecc.postpad;
		}

		if (stat == -EBADMSG &&
		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
			/* check for empty pages with bitflips */
			stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
							   oob - eccpadbytes,
							   eccpadbytes,
							   NULL, 0,
							   chip->ecc.strength);
		}

		if (stat < 0) {
			mtd->ecc_stats.failed++;
		} else {
			mtd->ecc_stats.corrected += stat;
			max_bitflips = max_t(unsigned int, max_bitflips, stat);
		}
	}

	/* Calculate remaining oob bytes */
	i = mtd->oobsize - (oob - chip->oob_poi);
	if (i) {
		ret = nand_read_data_op(chip, oob, i, false);
		if (ret)
			return ret;
	}

	return max_bitflips;
}

/**
 * nand_transfer_oob - [INTERN] Transfer oob to client buffer
 * @mtd: mtd info structure
 * @oob: oob destination address
 * @ops: oob ops structure
 * @len: size of oob to transfer
 */
static uint8_t *nand_transfer_oob(struct mtd_info *mtd, uint8_t *oob,
				  struct mtd_oob_ops *ops, size_t len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	int ret;

	switch (ops->mode) {

	case MTD_OPS_PLACE_OOB:
	case MTD_OPS_RAW:
		memcpy(oob, chip->oob_poi + ops->ooboffs, len);
		return oob + len;

	case MTD_OPS_AUTO_OOB:
		ret = mtd_ooblayout_get_databytes(mtd, oob, chip->oob_poi,
						  ops->ooboffs, len);
		BUG_ON(ret);
		return oob + len;

	default:
		BUG();
	}
	return NULL;
}

/**
 * nand_setup_read_retry - [INTERN] Set the READ RETRY mode
 * @mtd: MTD device structure
 * @retry_mode: the retry mode to use
 *
 * Some vendors supply a special command to shift the Vt threshold, to be used
 * when there are too many bitflips in a page (i.e., ECC error). After setting
 * a new threshold, the host should retry reading the page.
 */
static int nand_setup_read_retry(struct mtd_info *mtd, int retry_mode)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	pr_debug("setting READ RETRY mode %d\n", retry_mode);

	if (retry_mode >= chip->read_retries)
		return -EINVAL;

	if (!chip->setup_read_retry)
		return -EOPNOTSUPP;

	return chip->setup_read_retry(mtd, retry_mode);
}

/**
 * nand_do_read_ops - [INTERN] Read data with ECC
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob ops structure
 *
 * Internal function. Called with chip held.
 */
static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
			    struct mtd_oob_ops *ops)
{
	int chipnr, page, realpage, col, bytes, aligned, oob_required;
	struct nand_chip *chip = mtd_to_nand(mtd);
	int ret = 0;
	uint32_t readlen = ops->len;
	uint32_t oobreadlen = ops->ooblen;
	uint32_t max_oobsize = mtd_oobavail(mtd, ops);

	uint8_t *bufpoi, *oob, *buf;
	int use_bufpoi;
	unsigned int max_bitflips = 0;
	int retry_mode = 0;
	bool ecc_fail = false;

	chipnr = (int)(from >> chip->chip_shift);
	chip->select_chip(mtd, chipnr);

	realpage = (int)(from >> chip->page_shift);
	page = realpage & chip->pagemask;

	col = (int)(from & (mtd->writesize - 1));

	buf = ops->datbuf;
	oob = ops->oobbuf;
	oob_required = oob ? 1 : 0;

	while (1) {
		unsigned int ecc_failures = mtd->ecc_stats.failed;

		bytes = min(mtd->writesize - col, readlen);
		aligned = (bytes == mtd->writesize);

		if (!aligned)
			use_bufpoi = 1;
		else if (chip->options & NAND_USE_BOUNCE_BUFFER)
			use_bufpoi = !virt_addr_valid(buf) ||
				     !IS_ALIGNED((unsigned long)buf,
						 chip->buf_align);
		else
			use_bufpoi = 0;

		/* Is the current page in the buffer? */
		if (realpage != chip->pagebuf || oob) {
			bufpoi = use_bufpoi ? chip->data_buf : buf;

			if (use_bufpoi && aligned)
				pr_debug("%s: using read bounce buffer for buf@%p\n",
						 __func__, buf);

read_retry:
			/*
			 * Now read the page into the buffer.  Absent an error,
			 * the read methods return max bitflips per ecc step.
			 */
			if (unlikely(ops->mode == MTD_OPS_RAW))
				ret = chip->ecc.read_page_raw(mtd, chip, bufpoi,
							      oob_required,
							      page);
			else if (!aligned && NAND_HAS_SUBPAGE_READ(chip) &&
				 !oob)
				ret = chip->ecc.read_subpage(mtd, chip,
							col, bytes, bufpoi,
							page);
			else
				ret = chip->ecc.read_page(mtd, chip, bufpoi,
							  oob_required, page);
			if (ret < 0) {
				if (use_bufpoi)
					/* Invalidate page cache */
					chip->pagebuf = -1;
				break;
			}

			/* Transfer not aligned data */
			if (use_bufpoi) {
				if (!NAND_HAS_SUBPAGE_READ(chip) && !oob &&
				    !(mtd->ecc_stats.failed - ecc_failures) &&
				    (ops->mode != MTD_OPS_RAW)) {
					chip->pagebuf = realpage;
					chip->pagebuf_bitflips = ret;
				} else {
					/* Invalidate page cache */
					chip->pagebuf = -1;
				}
				memcpy(buf, chip->data_buf + col, bytes);
			}

			if (unlikely(oob)) {
				int toread = min(oobreadlen, max_oobsize);

				if (toread) {
					oob = nand_transfer_oob(mtd,
						oob, ops, toread);
					oobreadlen -= toread;
				}
			}

			if (chip->options & NAND_NEED_READRDY) {
				/* Apply delay or wait for ready/busy pin */
				if (!chip->dev_ready)
					udelay(chip->chip_delay);
				else
					nand_wait_ready(mtd);
			}

			if (mtd->ecc_stats.failed - ecc_failures) {
				if (retry_mode + 1 < chip->read_retries) {
					retry_mode++;
					ret = nand_setup_read_retry(mtd,
							retry_mode);
					if (ret < 0)
						break;

					/* Reset failures; retry */
					mtd->ecc_stats.failed = ecc_failures;
					goto read_retry;
				} else {
					/* No more retry modes; real failure */
					ecc_fail = true;
				}
			}

			buf += bytes;
			max_bitflips = max_t(unsigned int, max_bitflips, ret);
		} else {
			memcpy(buf, chip->data_buf + col, bytes);
			buf += bytes;
			max_bitflips = max_t(unsigned int, max_bitflips,
					     chip->pagebuf_bitflips);
		}

		readlen -= bytes;

		/* Reset to retry mode 0 */
		if (retry_mode) {
			ret = nand_setup_read_retry(mtd, 0);
			if (ret < 0)
				break;
			retry_mode = 0;
		}

		if (!readlen)
			break;

		/* For subsequent reads align to page boundary */
		col = 0;
		/* Increment page address */
		realpage++;

		page = realpage & chip->pagemask;
		/* Check, if we cross a chip boundary */
		if (!page) {
			chipnr++;
			chip->select_chip(mtd, -1);
			chip->select_chip(mtd, chipnr);
		}
	}
	chip->select_chip(mtd, -1);

	ops->retlen = ops->len - (size_t) readlen;
	if (oob)
		ops->oobretlen = ops->ooblen - oobreadlen;

	if (ret < 0)
		return ret;

	if (ecc_fail)
		return -EBADMSG;

	return max_bitflips;
}

/**
 * nand_read_oob_std - [REPLACEABLE] the most common OOB data read function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to read
 */
int nand_read_oob_std(struct mtd_info *mtd, struct nand_chip *chip, int page)
{
	return nand_read_oob_op(chip, page, 0, chip->oob_poi, mtd->oobsize);
}
EXPORT_SYMBOL(nand_read_oob_std);

/**
 * nand_read_oob_syndrome - [REPLACEABLE] OOB data read function for HW ECC
 *			    with syndromes
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to read
 */
int nand_read_oob_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
			   int page)
{
	int length = mtd->oobsize;
	int chunk = chip->ecc.bytes + chip->ecc.prepad + chip->ecc.postpad;
	int eccsize = chip->ecc.size;
	uint8_t *bufpoi = chip->oob_poi;
	int i, toread, sndrnd = 0, pos, ret;

	ret = nand_read_page_op(chip, page, chip->ecc.size, NULL, 0);
	if (ret)
		return ret;

	for (i = 0; i < chip->ecc.steps; i++) {
		if (sndrnd) {
			int ret;

			pos = eccsize + i * (eccsize + chunk);
			if (mtd->writesize > 512)
				ret = nand_change_read_column_op(chip, pos,
								 NULL, 0,
								 false);
			else
				ret = nand_read_page_op(chip, page, pos, NULL,
							0);

			if (ret)
				return ret;
		} else
			sndrnd = 1;
		toread = min_t(int, length, chunk);

		ret = nand_read_data_op(chip, bufpoi, toread, false);
		if (ret)
			return ret;

		bufpoi += toread;
		length -= toread;
	}
	if (length > 0) {
		ret = nand_read_data_op(chip, bufpoi, length, false);
		if (ret)
			return ret;
	}

	return 0;
}
EXPORT_SYMBOL(nand_read_oob_syndrome);

/**
 * nand_write_oob_std - [REPLACEABLE] the most common OOB data write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to write
 */
int nand_write_oob_std(struct mtd_info *mtd, struct nand_chip *chip, int page)
{
	return nand_prog_page_op(chip, page, mtd->writesize, chip->oob_poi,
				 mtd->oobsize);
}
EXPORT_SYMBOL(nand_write_oob_std);

/**
 * nand_write_oob_syndrome - [REPLACEABLE] OOB data write function for HW ECC
 *			     with syndrome - only for large page flash
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @page: page number to write
 */
int nand_write_oob_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
			    int page)
{
	int chunk = chip->ecc.bytes + chip->ecc.prepad + chip->ecc.postpad;
	int eccsize = chip->ecc.size, length = mtd->oobsize;
	int ret, i, len, pos, sndcmd = 0, steps = chip->ecc.steps;
	const uint8_t *bufpoi = chip->oob_poi;

	/*
	 * data-ecc-data-ecc ... ecc-oob
	 * or
	 * data-pad-ecc-pad-data-pad .... ecc-pad-oob
	 */
	if (!chip->ecc.prepad && !chip->ecc.postpad) {
		pos = steps * (eccsize + chunk);
		steps = 0;
	} else
		pos = eccsize;

	ret = nand_prog_page_begin_op(chip, page, pos, NULL, 0);
	if (ret)
		return ret;

	for (i = 0; i < steps; i++) {
		if (sndcmd) {
			if (mtd->writesize <= 512) {
				uint32_t fill = 0xFFFFFFFF;

				len = eccsize;
				while (len > 0) {
					int num = min_t(int, len, 4);

					ret = nand_write_data_op(chip, &fill,
								 num, false);
					if (ret)
						return ret;

					len -= num;
				}
			} else {
				pos = eccsize + i * (eccsize + chunk);
				ret = nand_change_write_column_op(chip, pos,
								  NULL, 0,
								  false);
				if (ret)
					return ret;
			}
		} else
			sndcmd = 1;
		len = min_t(int, length, chunk);

		ret = nand_write_data_op(chip, bufpoi, len, false);
		if (ret)
			return ret;

		bufpoi += len;
		length -= len;
	}
	if (length > 0) {
		ret = nand_write_data_op(chip, bufpoi, length, false);
		if (ret)
			return ret;
	}

	return nand_prog_page_end_op(chip);
}
EXPORT_SYMBOL(nand_write_oob_syndrome);

/**
 * nand_do_read_oob - [INTERN] NAND read out-of-band
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob operations description structure
 *
 * NAND read out-of-band data from the spare area.
 */
static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
			    struct mtd_oob_ops *ops)
{
	unsigned int max_bitflips = 0;
	int page, realpage, chipnr;
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct mtd_ecc_stats stats;
	int readlen = ops->ooblen;
	int len;
	uint8_t *buf = ops->oobbuf;
	int ret = 0;

	pr_debug("%s: from = 0x%08Lx, len = %i\n",
			__func__, (unsigned long long)from, readlen);

	stats = mtd->ecc_stats;

	len = mtd_oobavail(mtd, ops);

	chipnr = (int)(from >> chip->chip_shift);
	chip->select_chip(mtd, chipnr);

	/* Shift to get page */
	realpage = (int)(from >> chip->page_shift);
	page = realpage & chip->pagemask;

	while (1) {
		if (ops->mode == MTD_OPS_RAW)
			ret = chip->ecc.read_oob_raw(mtd, chip, page);
		else
			ret = chip->ecc.read_oob(mtd, chip, page);

		if (ret < 0)
			break;

		len = min(len, readlen);
		buf = nand_transfer_oob(mtd, buf, ops, len);

		if (chip->options & NAND_NEED_READRDY) {
			/* Apply delay or wait for ready/busy pin */
			if (!chip->dev_ready)
				udelay(chip->chip_delay);
			else
				nand_wait_ready(mtd);
		}

		max_bitflips = max_t(unsigned int, max_bitflips, ret);

		readlen -= len;
		if (!readlen)
			break;

		/* Increment page address */
		realpage++;

		page = realpage & chip->pagemask;
		/* Check, if we cross a chip boundary */
		if (!page) {
			chipnr++;
			chip->select_chip(mtd, -1);
			chip->select_chip(mtd, chipnr);
		}
	}
	chip->select_chip(mtd, -1);

	ops->oobretlen = ops->ooblen - readlen;

	if (ret < 0)
		return ret;

	if (mtd->ecc_stats.failed - stats.failed)
		return -EBADMSG;

	return max_bitflips;
}

/**
 * nand_read_oob - [MTD Interface] NAND read data and/or out-of-band
 * @mtd: MTD device structure
 * @from: offset to read from
 * @ops: oob operation description structure
 *
 * NAND read data and/or out-of-band data.
 */
static int nand_read_oob(struct mtd_info *mtd, loff_t from,
			 struct mtd_oob_ops *ops)
{
	int ret;

	ops->retlen = 0;

	if (ops->mode != MTD_OPS_PLACE_OOB &&
	    ops->mode != MTD_OPS_AUTO_OOB &&
	    ops->mode != MTD_OPS_RAW)
		return -ENOTSUPP;

	nand_get_device(mtd, FL_READING);

	if (!ops->datbuf)
		ret = nand_do_read_oob(mtd, from, ops);
	else
		ret = nand_do_read_ops(mtd, from, ops);

	nand_release_device(mtd);
	return ret;
}

/**
 * nand_write_page_raw_notsupp - dummy raw page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * Returns -ENOTSUPP unconditionally.
 */
int nand_write_page_raw_notsupp(struct mtd_info *mtd, struct nand_chip *chip,
				const u8 *buf, int oob_required, int page)
{
	return -ENOTSUPP;
}
EXPORT_SYMBOL(nand_write_page_raw_notsupp);

/**
 * nand_write_page_raw - [INTERN] raw page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * Not for syndrome calculating ECC controllers, which use a special oob layout.
 */
int nand_write_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
			const uint8_t *buf, int oob_required, int page)
{
	int ret;

	ret = nand_prog_page_begin_op(chip, page, 0, buf, mtd->writesize);
	if (ret)
		return ret;

	if (oob_required) {
		ret = nand_write_data_op(chip, chip->oob_poi, mtd->oobsize,
					 false);
		if (ret)
			return ret;
	}

	return nand_prog_page_end_op(chip);
}
EXPORT_SYMBOL(nand_write_page_raw);

/**
 * nand_write_page_raw_syndrome - [INTERN] raw page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * We need a special oob layout and handling even when ECC isn't checked.
 */
static int nand_write_page_raw_syndrome(struct mtd_info *mtd,
					struct nand_chip *chip,
					const uint8_t *buf, int oob_required,
					int page)
{
	int eccsize = chip->ecc.size;
	int eccbytes = chip->ecc.bytes;
	uint8_t *oob = chip->oob_poi;
	int steps, size, ret;

	ret = nand_prog_page_begin_op(chip, page, 0, NULL, 0);
	if (ret)
		return ret;

	for (steps = chip->ecc.steps; steps > 0; steps--) {
		ret = nand_write_data_op(chip, buf, eccsize, false);
		if (ret)
			return ret;

		buf += eccsize;

		if (chip->ecc.prepad) {
			ret = nand_write_data_op(chip, oob, chip->ecc.prepad,
						 false);
			if (ret)
				return ret;

			oob += chip->ecc.prepad;
		}

		ret = nand_write_data_op(chip, oob, eccbytes, false);
		if (ret)
			return ret;

		oob += eccbytes;

		if (chip->ecc.postpad) {
			ret = nand_write_data_op(chip, oob, chip->ecc.postpad,
						 false);
			if (ret)
				return ret;

			oob += chip->ecc.postpad;
		}
	}

	size = mtd->oobsize - (oob - chip->oob_poi);
	if (size) {
		ret = nand_write_data_op(chip, oob, size, false);
		if (ret)
			return ret;
	}

	return nand_prog_page_end_op(chip);
}
/**
 * nand_write_page_swecc - [REPLACEABLE] software ECC based page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
				 const uint8_t *buf, int oob_required,
				 int page)
{
	int i, eccsize = chip->ecc.size, ret;
	int eccbytes = chip->ecc.bytes;
	int eccsteps = chip->ecc.steps;
	uint8_t *ecc_calc = chip->ecc.calc_buf;
	const uint8_t *p = buf;

	/* Software ECC calculation */
	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize)
		chip->ecc.calculate(mtd, p, &ecc_calc[i]);

	ret = mtd_ooblayout_set_eccbytes(mtd, ecc_calc, chip->oob_poi, 0,
					 chip->ecc.total);
	if (ret)
		return ret;

	return chip->ecc.write_page_raw(mtd, chip, buf, 1, page);
}

/**
 * nand_write_page_hwecc - [REPLACEABLE] hardware ECC based page write function
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
				  const uint8_t *buf, int oob_required,
				  int page)
{
	int i, eccsize = chip->ecc.size, ret;
	int eccbytes = chip->ecc.bytes;
	int eccsteps = chip->ecc.steps;
	uint8_t *ecc_calc = chip->ecc.calc_buf;
	const uint8_t *p = buf;

	ret = nand_prog_page_begin_op(chip, page, 0, NULL, 0);
	if (ret)
		return ret;

	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
		chip->ecc.hwctl(mtd, NAND_ECC_WRITE);

		ret = nand_write_data_op(chip, p, eccsize, false);
		if (ret)
			return ret;

		chip->ecc.calculate(mtd, p, &ecc_calc[i]);
	}

	ret = mtd_ooblayout_set_eccbytes(mtd, ecc_calc, chip->oob_poi, 0,
					 chip->ecc.total);
	if (ret)
		return ret;

	ret = nand_write_data_op(chip, chip->oob_poi, mtd->oobsize, false);
	if (ret)
		return ret;

	return nand_prog_page_end_op(chip);
}


/**
 * nand_write_subpage_hwecc - [REPLACEABLE] hardware ECC based subpage write
 * @mtd:	mtd info structure
 * @chip:	nand chip info structure
 * @offset:	column address of subpage within the page
 * @data_len:	data length
 * @buf:	data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 */
static int nand_write_subpage_hwecc(struct mtd_info *mtd,
				struct nand_chip *chip, uint32_t offset,
				uint32_t data_len, const uint8_t *buf,
				int oob_required, int page)
{
	uint8_t *oob_buf  = chip->oob_poi;
	uint8_t *ecc_calc = chip->ecc.calc_buf;
	int ecc_size      = chip->ecc.size;
	int ecc_bytes     = chip->ecc.bytes;
	int ecc_steps     = chip->ecc.steps;
	uint32_t start_step = offset / ecc_size;
	uint32_t end_step   = (offset + data_len - 1) / ecc_size;
	int oob_bytes       = mtd->oobsize / ecc_steps;
	int step, ret;

	ret = nand_prog_page_begin_op(chip, page, 0, NULL, 0);
	if (ret)
		return ret;

	for (step = 0; step < ecc_steps; step++) {
		/* configure controller for WRITE access */
		chip->ecc.hwctl(mtd, NAND_ECC_WRITE);

		/* write data (untouched subpages already masked by 0xFF) */
		ret = nand_write_data_op(chip, buf, ecc_size, false);
		if (ret)
			return ret;

		/* mask ECC of un-touched subpages by padding 0xFF */
		if ((step < start_step) || (step > end_step))
			memset(ecc_calc, 0xff, ecc_bytes);
		else
			chip->ecc.calculate(mtd, buf, ecc_calc);

		/* mask OOB of un-touched subpages by padding 0xFF */
		/* if oob_required, preserve OOB metadata of written subpage */
		if (!oob_required || (step < start_step) || (step > end_step))
			memset(oob_buf, 0xff, oob_bytes);

		buf += ecc_size;
		ecc_calc += ecc_bytes;
		oob_buf  += oob_bytes;
	}

	/* copy calculated ECC for whole page to chip->buffer->oob */
	/* this include masked-value(0xFF) for unwritten subpages */
	ecc_calc = chip->ecc.calc_buf;
	ret = mtd_ooblayout_set_eccbytes(mtd, ecc_calc, chip->oob_poi, 0,
					 chip->ecc.total);
	if (ret)
		return ret;

	/* write OOB buffer to NAND device */
	ret = nand_write_data_op(chip, chip->oob_poi, mtd->oobsize, false);
	if (ret)
		return ret;

	return nand_prog_page_end_op(chip);
}


/**
 * nand_write_page_syndrome - [REPLACEABLE] hardware ECC syndrome based page write
 * @mtd: mtd info structure
 * @chip: nand chip info structure
 * @buf: data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * The hw generator calculates the error syndrome automatically. Therefore we
 * need a special oob layout and handling.
 */
static int nand_write_page_syndrome(struct mtd_info *mtd,
				    struct nand_chip *chip,
				    const uint8_t *buf, int oob_required,
				    int page)
{
	int i, eccsize = chip->ecc.size;
	int eccbytes = chip->ecc.bytes;
	int eccsteps = chip->ecc.steps;
	const uint8_t *p = buf;
	uint8_t *oob = chip->oob_poi;
	int ret;

	ret = nand_prog_page_begin_op(chip, page, 0, NULL, 0);
	if (ret)
		return ret;

	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
		chip->ecc.hwctl(mtd, NAND_ECC_WRITE);

		ret = nand_write_data_op(chip, p, eccsize, false);
		if (ret)
			return ret;

		if (chip->ecc.prepad) {
			ret = nand_write_data_op(chip, oob, chip->ecc.prepad,
						 false);
			if (ret)
				return ret;

			oob += chip->ecc.prepad;
		}

		chip->ecc.calculate(mtd, p, oob);

		ret = nand_write_data_op(chip, oob, eccbytes, false);
		if (ret)
			return ret;

		oob += eccbytes;

		if (chip->ecc.postpad) {
			ret = nand_write_data_op(chip, oob, chip->ecc.postpad,
						 false);
			if (ret)
				return ret;

			oob += chip->ecc.postpad;
		}
	}

	/* Calculate remaining oob bytes */
	i = mtd->oobsize - (oob - chip->oob_poi);
	if (i) {
		ret = nand_write_data_op(chip, oob, i, false);
		if (ret)
			return ret;
	}

	return nand_prog_page_end_op(chip);
}

/**
 * nand_write_page - write one page
 * @mtd: MTD device structure
 * @chip: NAND chip descriptor
 * @offset: address offset within the page
 * @data_len: length of actual data to be written
 * @buf: the data to write
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 * @raw: use _raw version of write_page
 */
static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
		uint32_t offset, int data_len, const uint8_t *buf,
		int oob_required, int page, int raw)
{
	int status, subpage;

	if (!(chip->options & NAND_NO_SUBPAGE_WRITE) &&
		chip->ecc.write_subpage)
		subpage = offset || (data_len < mtd->writesize);
	else
		subpage = 0;

	if (unlikely(raw))
		status = chip->ecc.write_page_raw(mtd, chip, buf,
						  oob_required, page);
	else if (subpage)
		status = chip->ecc.write_subpage(mtd, chip, offset, data_len,
						 buf, oob_required, page);
	else
		status = chip->ecc.write_page(mtd, chip, buf, oob_required,
					      page);

	if (status < 0)
		return status;

	return 0;
}

/**
 * nand_fill_oob - [INTERN] Transfer client buffer to oob
 * @mtd: MTD device structure
 * @oob: oob data buffer
 * @len: oob data write length
 * @ops: oob ops structure
 */
static uint8_t *nand_fill_oob(struct mtd_info *mtd, uint8_t *oob, size_t len,
			      struct mtd_oob_ops *ops)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	int ret;

	/*
	 * Initialise to all 0xFF, to avoid the possibility of left over OOB
	 * data from a previous OOB read.
	 */
	memset(chip->oob_poi, 0xff, mtd->oobsize);

	switch (ops->mode) {

	case MTD_OPS_PLACE_OOB:
	case MTD_OPS_RAW:
		memcpy(chip->oob_poi + ops->ooboffs, oob, len);
		return oob + len;

	case MTD_OPS_AUTO_OOB:
		ret = mtd_ooblayout_set_databytes(mtd, oob, chip->oob_poi,
						  ops->ooboffs, len);
		BUG_ON(ret);
		return oob + len;

	default:
		BUG();
	}
	return NULL;
}

#define NOTALIGNED(x)	((x & (chip->subpagesize - 1)) != 0)

/**
 * nand_do_write_ops - [INTERN] NAND write with ECC
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operations description structure
 *
 * NAND write with ECC.
 */
static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
			     struct mtd_oob_ops *ops)
{
	int chipnr, realpage, page, column;
	struct nand_chip *chip = mtd_to_nand(mtd);
	uint32_t writelen = ops->len;

	uint32_t oobwritelen = ops->ooblen;
	uint32_t oobmaxlen = mtd_oobavail(mtd, ops);

	uint8_t *oob = ops->oobbuf;
	uint8_t *buf = ops->datbuf;
	int ret;
	int oob_required = oob ? 1 : 0;

	ops->retlen = 0;
	if (!writelen)
		return 0;

	/* Reject writes, which are not page aligned */
	if (NOTALIGNED(to) || NOTALIGNED(ops->len)) {
		pr_notice("%s: attempt to write non page aligned data\n",
			   __func__);
		return -EINVAL;
	}

	column = to & (mtd->writesize - 1);

	chipnr = (int)(to >> chip->chip_shift);
	chip->select_chip(mtd, chipnr);

	/* Check, if it is write protected */
	if (nand_check_wp(mtd)) {
		ret = -EIO;
		goto err_out;
	}

	realpage = (int)(to >> chip->page_shift);
	page = realpage & chip->pagemask;

	/* Invalidate the page cache, when we write to the cached page */
	if (to <= ((loff_t)chip->pagebuf << chip->page_shift) &&
	    ((loff_t)chip->pagebuf << chip->page_shift) < (to + ops->len))
		chip->pagebuf = -1;

	/* Don't allow multipage oob writes with offset */
	if (oob && ops->ooboffs && (ops->ooboffs + ops->ooblen > oobmaxlen)) {
		ret = -EINVAL;
		goto err_out;
	}

	while (1) {
		int bytes = mtd->writesize;
		uint8_t *wbuf = buf;
		int use_bufpoi;
		int part_pagewr = (column || writelen < mtd->writesize);

		if (part_pagewr)
			use_bufpoi = 1;
		else if (chip->options & NAND_USE_BOUNCE_BUFFER)
			use_bufpoi = !virt_addr_valid(buf) ||
				     !IS_ALIGNED((unsigned long)buf,
						 chip->buf_align);
		else
			use_bufpoi = 0;

		/* Partial page write?, or need to use bounce buffer */
		if (use_bufpoi) {
			pr_debug("%s: using write bounce buffer for buf@%p\n",
					 __func__, buf);
			if (part_pagewr)
				bytes = min_t(int, bytes - column, writelen);
			chip->pagebuf = -1;
			memset(chip->data_buf, 0xff, mtd->writesize);
			memcpy(&chip->data_buf[column], buf, bytes);
			wbuf = chip->data_buf;
		}

		if (unlikely(oob)) {
			size_t len = min(oobwritelen, oobmaxlen);
			oob = nand_fill_oob(mtd, oob, len, ops);
			oobwritelen -= len;
		} else {
			/* We still need to erase leftover OOB data */
			memset(chip->oob_poi, 0xff, mtd->oobsize);
		}

		ret = nand_write_page(mtd, chip, column, bytes, wbuf,
				      oob_required, page,
				      (ops->mode == MTD_OPS_RAW));
		if (ret)
			break;

		writelen -= bytes;
		if (!writelen)
			break;

		column = 0;
		buf += bytes;
		realpage++;

		page = realpage & chip->pagemask;
		/* Check, if we cross a chip boundary */
		if (!page) {
			chipnr++;
			chip->select_chip(mtd, -1);
			chip->select_chip(mtd, chipnr);
		}
	}

	ops->retlen = ops->len - writelen;
	if (unlikely(oob))
		ops->oobretlen = ops->ooblen;

err_out:
	chip->select_chip(mtd, -1);
	return ret;
}

/**
 * panic_nand_write - [MTD Interface] NAND write with ECC
 * @mtd: MTD device structure
 * @to: offset to write to
 * @len: number of bytes to write
 * @retlen: pointer to variable to store the number of written bytes
 * @buf: the data to write
 *
 * NAND write with ECC. Used when performing writes in interrupt context, this
 * may for example be called by mtdoops when writing an oops while in panic.
 */
static int panic_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
			    size_t *retlen, const uint8_t *buf)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	int chipnr = (int)(to >> chip->chip_shift);
	struct mtd_oob_ops ops;
	int ret;

	/* Grab the device */
	panic_nand_get_device(chip, mtd, FL_WRITING);

	chip->select_chip(mtd, chipnr);

	/* Wait for the device to get ready */
	panic_nand_wait(mtd, chip, 400);

	memset(&ops, 0, sizeof(ops));
	ops.len = len;
	ops.datbuf = (uint8_t *)buf;
	ops.mode = MTD_OPS_PLACE_OOB;

	ret = nand_do_write_ops(mtd, to, &ops);

	*retlen = ops.retlen;
	return ret;
}

/**
 * nand_do_write_oob - [MTD Interface] NAND write out-of-band
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operation description structure
 *
 * NAND write out-of-band.
 */
static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
			     struct mtd_oob_ops *ops)
{
	int chipnr, page, status, len;
	struct nand_chip *chip = mtd_to_nand(mtd);

	pr_debug("%s: to = 0x%08x, len = %i\n",
			 __func__, (unsigned int)to, (int)ops->ooblen);

	len = mtd_oobavail(mtd, ops);

	/* Do not allow write past end of page */
	if ((ops->ooboffs + ops->ooblen) > len) {
		pr_debug("%s: attempt to write past end of page\n",
				__func__);
		return -EINVAL;
	}

	chipnr = (int)(to >> chip->chip_shift);

	/*
	 * Reset the chip. Some chips (like the Toshiba TC5832DC found in one
	 * of my DiskOnChip 2000 test units) will clear the whole data page too
	 * if we don't do this. I have no clue why, but I seem to have 'fixed'
	 * it in the doc2000 driver in August 1999.  dwmw2.
	 */
	nand_reset(chip, chipnr);

	chip->select_chip(mtd, chipnr);

	/* Shift to get page */
	page = (int)(to >> chip->page_shift);

	/* Check, if it is write protected */
	if (nand_check_wp(mtd)) {
		chip->select_chip(mtd, -1);
		return -EROFS;
	}

	/* Invalidate the page cache, if we write to the cached page */
	if (page == chip->pagebuf)
		chip->pagebuf = -1;

	nand_fill_oob(mtd, ops->oobbuf, ops->ooblen, ops);

	if (ops->mode == MTD_OPS_RAW)
		status = chip->ecc.write_oob_raw(mtd, chip, page & chip->pagemask);
	else
		status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);

	chip->select_chip(mtd, -1);

	if (status)
		return status;

	ops->oobretlen = ops->ooblen;

	return 0;
}

/**
 * nand_write_oob - [MTD Interface] NAND write data and/or out-of-band
 * @mtd: MTD device structure
 * @to: offset to write to
 * @ops: oob operation description structure
 */
static int nand_write_oob(struct mtd_info *mtd, loff_t to,
			  struct mtd_oob_ops *ops)
{
	int ret = -ENOTSUPP;

	ops->retlen = 0;

	nand_get_device(mtd, FL_WRITING);

	switch (ops->mode) {
	case MTD_OPS_PLACE_OOB:
	case MTD_OPS_AUTO_OOB:
	case MTD_OPS_RAW:
		break;

	default:
		goto out;
	}

	if (!ops->datbuf)
		ret = nand_do_write_oob(mtd, to, ops);
	else
		ret = nand_do_write_ops(mtd, to, ops);

out:
	nand_release_device(mtd);
	return ret;
}

/**
 * single_erase - [GENERIC] NAND standard block erase command function
 * @mtd: MTD device structure
 * @page: the page address of the block which will be erased
 *
 * Standard erase command for NAND chips. Returns NAND status.
 */
static int single_erase(struct mtd_info *mtd, int page)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	unsigned int eraseblock;

	/* Send commands to erase a block */
	eraseblock = page >> (chip->phys_erase_shift - chip->page_shift);

	return nand_erase_op(chip, eraseblock);
}

/**
 * nand_erase - [MTD Interface] erase block(s)
 * @mtd: MTD device structure
 * @instr: erase instruction
 *
 * Erase one ore more blocks.
 */
static int nand_erase(struct mtd_info *mtd, struct erase_info *instr)
{
	return nand_erase_nand(mtd, instr, 0);
}

/**
 * nand_erase_nand - [INTERN] erase block(s)
 * @mtd: MTD device structure
 * @instr: erase instruction
 * @allowbbt: allow erasing the bbt area
 *
 * Erase one ore more blocks.
 */
int nand_erase_nand(struct mtd_info *mtd, struct erase_info *instr,
		    int allowbbt)
{
	int page, status, pages_per_block, ret, chipnr;
	struct nand_chip *chip = mtd_to_nand(mtd);
	loff_t len;

	pr_debug("%s: start = 0x%012llx, len = %llu\n",
			__func__, (unsigned long long)instr->addr,
			(unsigned long long)instr->len);

	if (check_offs_len(mtd, instr->addr, instr->len))
		return -EINVAL;

	/* Grab the lock and see if the device is available */
	nand_get_device(mtd, FL_ERASING);

	/* Shift to get first page */
	page = (int)(instr->addr >> chip->page_shift);
	chipnr = (int)(instr->addr >> chip->chip_shift);

	/* Calculate pages in each block */
	pages_per_block = 1 << (chip->phys_erase_shift - chip->page_shift);

	/* Select the NAND device */
	chip->select_chip(mtd, chipnr);

	/* Check, if it is write protected */
	if (nand_check_wp(mtd)) {
		pr_debug("%s: device is write protected!\n",
				__func__);
		ret = -EIO;
		goto erase_exit;
	}

	/* Loop through the pages */
	len = instr->len;

	while (len) {
		/* Check if we have a bad block, we do not erase bad blocks! */
		if (nand_block_checkbad(mtd, ((loff_t) page) <<
					chip->page_shift, allowbbt)) {
			pr_warn("%s: attempt to erase a bad block at page 0x%08x\n",
				    __func__, page);
			ret = -EIO;
			goto erase_exit;
		}

		/*
		 * Invalidate the page cache, if we erase the block which
		 * contains the current cached page.
		 */
		if (page <= chip->pagebuf && chip->pagebuf <
		    (page + pages_per_block))
			chip->pagebuf = -1;

		status = chip->erase(mtd, page & chip->pagemask);

		/* See if block erase succeeded */
		if (status) {
			pr_debug("%s: failed erase, page 0x%08x\n",
					__func__, page);
			ret = -EIO;
			instr->fail_addr =
				((loff_t)page << chip->page_shift);
			goto erase_exit;
		}

		/* Increment page address and decrement length */
		len -= (1ULL << chip->phys_erase_shift);
		page += pages_per_block;

		/* Check, if we cross a chip boundary */
		if (len && !(page & chip->pagemask)) {
			chipnr++;
			chip->select_chip(mtd, -1);
			chip->select_chip(mtd, chipnr);
		}
	}

	ret = 0;
erase_exit:

	/* Deselect and wake up anyone waiting on the device */
	chip->select_chip(mtd, -1);
	nand_release_device(mtd);

	/* Return more or less happy */
	return ret;
}

/**
 * nand_sync - [MTD Interface] sync
 * @mtd: MTD device structure
 *
 * Sync is actually a wait for chip ready function.
 */
static void nand_sync(struct mtd_info *mtd)
{
	pr_debug("%s: called\n", __func__);

	/* Grab the lock and see if the device is available */
	nand_get_device(mtd, FL_SYNCING);
	/* Release it and go back */
	nand_release_device(mtd);
}

/**
 * nand_block_isbad - [MTD Interface] Check if block at offset is bad
 * @mtd: MTD device structure
 * @offs: offset relative to mtd start
 */
static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	int chipnr = (int)(offs >> chip->chip_shift);
	int ret;

	/* Select the NAND device */
	nand_get_device(mtd, FL_READING);
	chip->select_chip(mtd, chipnr);

	ret = nand_block_checkbad(mtd, offs, 0);

	chip->select_chip(mtd, -1);
	nand_release_device(mtd);

	return ret;
}

/**
 * nand_block_markbad - [MTD Interface] Mark block at the given offset as bad
 * @mtd: MTD device structure
 * @ofs: offset relative to mtd start
 */
static int nand_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
	int ret;

	ret = nand_block_isbad(mtd, ofs);
	if (ret) {
		/* If it was bad already, return success and do nothing */
		if (ret > 0)
			return 0;
		return ret;
	}

	return nand_block_markbad_lowlevel(mtd, ofs);
}

/**
 * nand_max_bad_blocks - [MTD Interface] Max number of bad blocks for an mtd
 * @mtd: MTD device structure
 * @ofs: offset relative to mtd start
 * @len: length of mtd
 */
static int nand_max_bad_blocks(struct mtd_info *mtd, loff_t ofs, size_t len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	u32 part_start_block;
	u32 part_end_block;
	u32 part_start_die;
	u32 part_end_die;

	/*
	 * max_bb_per_die and blocks_per_die used to determine
	 * the maximum bad block count.
	 */
	if (!chip->max_bb_per_die || !chip->blocks_per_die)
		return -ENOTSUPP;

	/* Get the start and end of the partition in erase blocks. */
	part_start_block = mtd_div_by_eb(ofs, mtd);
	part_end_block = mtd_div_by_eb(len, mtd) + part_start_block - 1;

	/* Get the start and end LUNs of the partition. */
	part_start_die = part_start_block / chip->blocks_per_die;
	part_end_die = part_end_block / chip->blocks_per_die;

	/*
	 * Look up the bad blocks per unit and multiply by the number of units
	 * that the partition spans.
	 */
	return chip->max_bb_per_die * (part_end_die - part_start_die + 1);
}

/**
 * nand_default_set_features- [REPLACEABLE] set NAND chip features
 * @mtd: MTD device structure
 * @chip: nand chip info structure
 * @addr: feature address.
 * @subfeature_param: the subfeature parameters, a four bytes array.
 */
static int nand_default_set_features(struct mtd_info *mtd,
				     struct nand_chip *chip, int addr,
				     uint8_t *subfeature_param)
{
	return nand_set_features_op(chip, addr, subfeature_param);
}

/**
 * nand_default_get_features- [REPLACEABLE] get NAND chip features
 * @mtd: MTD device structure
 * @chip: nand chip info structure
 * @addr: feature address.
 * @subfeature_param: the subfeature parameters, a four bytes array.
 */
static int nand_default_get_features(struct mtd_info *mtd,
				     struct nand_chip *chip, int addr,
				     uint8_t *subfeature_param)
{
	return nand_get_features_op(chip, addr, subfeature_param);
}

/**
 * nand_get_set_features_notsupp - set/get features stub returning -ENOTSUPP
 * @mtd: MTD device structure
 * @chip: nand chip info structure
 * @addr: feature address.
 * @subfeature_param: the subfeature parameters, a four bytes array.
 *
 * Should be used by NAND controller drivers that do not support the SET/GET
 * FEATURES operations.
 */
int nand_get_set_features_notsupp(struct mtd_info *mtd, struct nand_chip *chip,
				  int addr, u8 *subfeature_param)
{
	return -ENOTSUPP;
}
EXPORT_SYMBOL(nand_get_set_features_notsupp);

/**
 * nand_suspend - [MTD Interface] Suspend the NAND flash
 * @mtd: MTD device structure
 */
static int nand_suspend(struct mtd_info *mtd)
{
	return nand_get_device(mtd, FL_PM_SUSPENDED);
}

/**
 * nand_resume - [MTD Interface] Resume the NAND flash
 * @mtd: MTD device structure
 */
static void nand_resume(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);

	if (chip->state == FL_PM_SUSPENDED)
		nand_release_device(mtd);
	else
		pr_err("%s called for a chip which is not in suspended state\n",
			__func__);
}

/**
 * nand_shutdown - [MTD Interface] Finish the current NAND operation and
 *                 prevent further operations
 * @mtd: MTD device structure
 */
static void nand_shutdown(struct mtd_info *mtd)
{
	nand_get_device(mtd, FL_PM_SUSPENDED);
}

/* Set default functions */
static void nand_set_defaults(struct nand_chip *chip)
{
	unsigned int busw = chip->options & NAND_BUSWIDTH_16;

	/* check for proper chip_delay setup, set 20us if not */
	if (!chip->chip_delay)
		chip->chip_delay = 20;

	/* check, if a user supplied command function given */
	if (!chip->cmdfunc && !chip->exec_op)
		chip->cmdfunc = nand_command;

	/* check, if a user supplied wait function given */
	if (chip->waitfunc == NULL)
		chip->waitfunc = nand_wait;

	if (!chip->select_chip)
		chip->select_chip = nand_select_chip;

	/* set for ONFI nand */
	if (!chip->set_features)
		chip->set_features = nand_default_set_features;
	if (!chip->get_features)
		chip->get_features = nand_default_get_features;

	/* If called twice, pointers that depend on busw may need to be reset */
	if (!chip->read_byte || chip->read_byte == nand_read_byte)
		chip->read_byte = busw ? nand_read_byte16 : nand_read_byte;
	if (!chip->read_word)
		chip->read_word = nand_read_word;
	if (!chip->block_bad)
		chip->block_bad = nand_block_bad;
	if (!chip->block_markbad)
		chip->block_markbad = nand_default_block_markbad;
	if (!chip->write_buf || chip->write_buf == nand_write_buf)
		chip->write_buf = busw ? nand_write_buf16 : nand_write_buf;
	if (!chip->write_byte || chip->write_byte == nand_write_byte)
		chip->write_byte = busw ? nand_write_byte16 : nand_write_byte;
	if (!chip->read_buf || chip->read_buf == nand_read_buf)
		chip->read_buf = busw ? nand_read_buf16 : nand_read_buf;

	if (!chip->controller) {
		chip->controller = &chip->dummy_controller;
		nand_controller_init(chip->controller);
	}

	if (!chip->buf_align)
		chip->buf_align = 1;
}

/* Sanitize ONFI strings so we can safely print them */
static void sanitize_string(uint8_t *s, size_t len)
{
	ssize_t i;

	/* Null terminate */
	s[len - 1] = 0;

	/* Remove non printable chars */
	for (i = 0; i < len - 1; i++) {
		if (s[i] < ' ' || s[i] > 127)
			s[i] = '?';
	}

	/* Remove trailing spaces */
	strim(s);
}

static u16 onfi_crc16(u16 crc, u8 const *p, size_t len)
{
	int i;
	while (len--) {
		crc ^= *p++ << 8;
		for (i = 0; i < 8; i++)
			crc = (crc << 1) ^ ((crc & 0x8000) ? 0x8005 : 0);
	}

	return crc;
}

/* Parse the Extended Parameter Page. */
static int nand_flash_detect_ext_param_page(struct nand_chip *chip,
					    struct nand_onfi_params *p)
{
	struct onfi_ext_param_page *ep;
	struct onfi_ext_section *s;
	struct onfi_ext_ecc_info *ecc;
	uint8_t *cursor;
	int ret;
	int len;
	int i;

	len = le16_to_cpu(p->ext_param_page_length) * 16;
	ep = kmalloc(len, GFP_KERNEL);
	if (!ep)
		return -ENOMEM;

	/* Send our own NAND_CMD_PARAM. */
	ret = nand_read_param_page_op(chip, 0, NULL, 0);
	if (ret)
		goto ext_out;

	/* Use the Change Read Column command to skip the ONFI param pages. */
	ret = nand_change_read_column_op(chip,
					 sizeof(*p) * p->num_of_param_pages,
					 ep, len, true);
	if (ret)
		goto ext_out;

	ret = -EINVAL;
	if ((onfi_crc16(ONFI_CRC_BASE, ((uint8_t *)ep) + 2, len - 2)
		!= le16_to_cpu(ep->crc))) {
		pr_debug("fail in the CRC.\n");
		goto ext_out;
	}

	/*
	 * Check the signature.
	 * Do not strictly follow the ONFI spec, maybe changed in future.
	 */
	if (strncmp(ep->sig, "EPPS", 4)) {
		pr_debug("The signature is invalid.\n");
		goto ext_out;
	}

	/* find the ECC section. */
	cursor = (uint8_t *)(ep + 1);
	for (i = 0; i < ONFI_EXT_SECTION_MAX; i++) {
		s = ep->sections + i;
		if (s->type == ONFI_SECTION_TYPE_2)
			break;
		cursor += s->length * 16;
	}
	if (i == ONFI_EXT_SECTION_MAX) {
		pr_debug("We can not find the ECC section.\n");
		goto ext_out;
	}

	/* get the info we want. */
	ecc = (struct onfi_ext_ecc_info *)cursor;

	if (!ecc->codeword_size) {
		pr_debug("Invalid codeword size\n");
		goto ext_out;
	}

	chip->ecc_strength_ds = ecc->ecc_bits;
	chip->ecc_step_ds = 1 << ecc->codeword_size;
	ret = 0;

ext_out:
	kfree(ep);
	return ret;
}

/*
 * Recover data with bit-wise majority
 */
static void nand_bit_wise_majority(const void **srcbufs,
				   unsigned int nsrcbufs,
				   void *dstbuf,
				   unsigned int bufsize)
{
	int i, j, k;

	for (i = 0; i < bufsize; i++) {
		u8 val = 0;

		for (j = 0; j < 8; j++) {
			unsigned int cnt = 0;

			for (k = 0; k < nsrcbufs; k++) {
				const u8 *srcbuf = srcbufs[k];

				if (srcbuf[i] & BIT(j))
					cnt++;
			}

			if (cnt > nsrcbufs / 2)
				val |= BIT(j);
		}

		((u8 *)dstbuf)[i] = val;
	}
}

/*
 * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
 */
static int nand_flash_detect_onfi(struct nand_chip *chip)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	struct nand_onfi_params *p;
	struct onfi_params *onfi;
	int onfi_version = 0;
	char id[4];
	int i, ret, val;

	/* Try ONFI for unknown chip or LP */
	ret = nand_readid_op(chip, 0x20, id, sizeof(id));
	if (ret || strncmp(id, "ONFI", 4))
		return 0;

	/* ONFI chip: allocate a buffer to hold its parameter page */
	p = kzalloc((sizeof(*p) * 3), GFP_KERNEL);
	if (!p)
		return -ENOMEM;

	ret = nand_read_param_page_op(chip, 0, NULL, 0);
	if (ret) {
		ret = 0;
		goto free_onfi_param_page;
	}

	for (i = 0; i < 3; i++) {
		ret = nand_read_data_op(chip, &p[i], sizeof(*p), true);
		if (ret) {
			ret = 0;
			goto free_onfi_param_page;
		}

		if (onfi_crc16(ONFI_CRC_BASE, (u8 *)&p[i], 254) ==
				le16_to_cpu(p->crc)) {
			if (i)
				memcpy(p, &p[i], sizeof(*p));
			break;
		}
	}

	if (i == 3) {
		const void *srcbufs[3] = {p, p + 1, p + 2};

		pr_warn("Could not find a valid ONFI parameter page, trying bit-wise majority to recover it\n");
		nand_bit_wise_majority(srcbufs, ARRAY_SIZE(srcbufs), p,
				       sizeof(*p));

		if (onfi_crc16(ONFI_CRC_BASE, (u8 *)p, 254) !=
				le16_to_cpu(p->crc)) {
			pr_err("ONFI parameter recovery failed, aborting\n");
			goto free_onfi_param_page;
		}
	}

	if (chip->manufacturer.desc && chip->manufacturer.desc->ops &&
	    chip->manufacturer.desc->ops->fixup_onfi_param_page)
		chip->manufacturer.desc->ops->fixup_onfi_param_page(chip, p);

	/* Check version */
	val = le16_to_cpu(p->revision);
	if (val & ONFI_VERSION_2_3)
		onfi_version = 23;
	else if (val & ONFI_VERSION_2_2)
		onfi_version = 22;
	else if (val & ONFI_VERSION_2_1)
		onfi_version = 21;
	else if (val & ONFI_VERSION_2_0)
		onfi_version = 20;
	else if (val & ONFI_VERSION_1_0)
		onfi_version = 10;

	if (!onfi_version) {
		pr_info("unsupported ONFI version: %d\n", val);
		goto free_onfi_param_page;
	}

	sanitize_string(p->manufacturer, sizeof(p->manufacturer));
	sanitize_string(p->model, sizeof(p->model));
	chip->parameters.model = kstrdup(p->model, GFP_KERNEL);
	if (!chip->parameters.model) {
		ret = -ENOMEM;
		goto free_onfi_param_page;
	}

	mtd->writesize = le32_to_cpu(p->byte_per_page);

	/*
	 * pages_per_block and blocks_per_lun may not be a power-of-2 size
	 * (don't ask me who thought of this...). MTD assumes that these
	 * dimensions will be power-of-2, so just truncate the remaining area.
	 */
	mtd->erasesize = 1 << (fls(le32_to_cpu(p->pages_per_block)) - 1);
	mtd->erasesize *= mtd->writesize;

	mtd->oobsize = le16_to_cpu(p->spare_bytes_per_page);

	/* See erasesize comment */
	chip->chipsize = 1 << (fls(le32_to_cpu(p->blocks_per_lun)) - 1);
	chip->chipsize *= (uint64_t)mtd->erasesize * p->lun_count;
	chip->bits_per_cell = p->bits_per_cell;

	chip->max_bb_per_die = le16_to_cpu(p->bb_per_lun);
	chip->blocks_per_die = le32_to_cpu(p->blocks_per_lun);

	if (le16_to_cpu(p->features) & ONFI_FEATURE_16_BIT_BUS)
		chip->options |= NAND_BUSWIDTH_16;

	if (p->ecc_bits != 0xff) {
		chip->ecc_strength_ds = p->ecc_bits;
		chip->ecc_step_ds = 512;
	} else if (onfi_version >= 21 &&
		(le16_to_cpu(p->features) & ONFI_FEATURE_EXT_PARAM_PAGE)) {

		/*
		 * The nand_flash_detect_ext_param_page() uses the
		 * Change Read Column command which maybe not supported
		 * by the chip->cmdfunc. So try to update the chip->cmdfunc
		 * now. We do not replace user supplied command function.
		 */
		if (mtd->writesize > 512 && chip->cmdfunc == nand_command)
			chip->cmdfunc = nand_command_lp;

		/* The Extended Parameter Page is supported since ONFI 2.1. */
		if (nand_flash_detect_ext_param_page(chip, p))
			pr_warn("Failed to detect ONFI extended param page\n");
	} else {
		pr_warn("Could not retrieve ONFI ECC requirements\n");
	}

	/* Save some parameters from the parameter page for future use */
	if (le16_to_cpu(p->opt_cmd) & ONFI_OPT_CMD_SET_GET_FEATURES) {
		chip->parameters.supports_set_get_features = true;
		bitmap_set(chip->parameters.get_feature_list,
			   ONFI_FEATURE_ADDR_TIMING_MODE, 1);
		bitmap_set(chip->parameters.set_feature_list,
			   ONFI_FEATURE_ADDR_TIMING_MODE, 1);
	}

	onfi = kzalloc(sizeof(*onfi), GFP_KERNEL);
	if (!onfi) {
		ret = -ENOMEM;
		goto free_model;
	}

	onfi->version = onfi_version;
	onfi->tPROG = le16_to_cpu(p->t_prog);
	onfi->tBERS = le16_to_cpu(p->t_bers);
	onfi->tR = le16_to_cpu(p->t_r);
	onfi->tCCS = le16_to_cpu(p->t_ccs);
	onfi->async_timing_mode = le16_to_cpu(p->async_timing_mode);
	onfi->vendor_revision = le16_to_cpu(p->vendor_revision);
	memcpy(onfi->vendor, p->vendor, sizeof(p->vendor));
	chip->parameters.onfi = onfi;

	/* Identification done, free the full ONFI parameter page and exit */
	kfree(p);

	return 1;

free_model:
	kfree(chip->parameters.model);
free_onfi_param_page:
	kfree(p);

	return ret;
}

/*
 * Check if the NAND chip is JEDEC compliant, returns 1 if it is, 0 otherwise.
 */
static int nand_flash_detect_jedec(struct nand_chip *chip)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	struct nand_jedec_params *p;
	struct jedec_ecc_info *ecc;
	int jedec_version = 0;
	char id[5];
	int i, val, ret;

	/* Try JEDEC for unknown chip or LP */
	ret = nand_readid_op(chip, 0x40, id, sizeof(id));
	if (ret || strncmp(id, "JEDEC", sizeof(id)))
		return 0;

	/* JEDEC chip: allocate a buffer to hold its parameter page */
	p = kzalloc(sizeof(*p), GFP_KERNEL);
	if (!p)
		return -ENOMEM;

	ret = nand_read_param_page_op(chip, 0x40, NULL, 0);
	if (ret) {
		ret = 0;
		goto free_jedec_param_page;
	}

	for (i = 0; i < 3; i++) {
		ret = nand_read_data_op(chip, p, sizeof(*p), true);
		if (ret) {
			ret = 0;
			goto free_jedec_param_page;
		}

		if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 510) ==
				le16_to_cpu(p->crc))
			break;
	}

	if (i == 3) {
		pr_err("Could not find valid JEDEC parameter page; aborting\n");
		goto free_jedec_param_page;
	}

	/* Check version */
	val = le16_to_cpu(p->revision);
	if (val & (1 << 2))
		jedec_version = 10;
	else if (val & (1 << 1))
		jedec_version = 1; /* vendor specific version */

	if (!jedec_version) {
		pr_info("unsupported JEDEC version: %d\n", val);
		goto free_jedec_param_page;
	}

	sanitize_string(p->manufacturer, sizeof(p->manufacturer));
	sanitize_string(p->model, sizeof(p->model));
	chip->parameters.model = kstrdup(p->model, GFP_KERNEL);
	if (!chip->parameters.model) {
		ret = -ENOMEM;
		goto free_jedec_param_page;
	}

	mtd->writesize = le32_to_cpu(p->byte_per_page);

	/* Please reference to the comment for nand_flash_detect_onfi. */
	mtd->erasesize = 1 << (fls(le32_to_cpu(p->pages_per_block)) - 1);
	mtd->erasesize *= mtd->writesize;

	mtd->oobsize = le16_to_cpu(p->spare_bytes_per_page);

	/* Please reference to the comment for nand_flash_detect_onfi. */
	chip->chipsize = 1 << (fls(le32_to_cpu(p->blocks_per_lun)) - 1);
	chip->chipsize *= (uint64_t)mtd->erasesize * p->lun_count;
	chip->bits_per_cell = p->bits_per_cell;

	if (le16_to_cpu(p->features) & JEDEC_FEATURE_16_BIT_BUS)
		chip->options |= NAND_BUSWIDTH_16;

	/* ECC info */
	ecc = &p->ecc_info[0];

	if (ecc->codeword_size >= 9) {
		chip->ecc_strength_ds = ecc->ecc_bits;
		chip->ecc_step_ds = 1 << ecc->codeword_size;
	} else {
		pr_warn("Invalid codeword size\n");
	}

free_jedec_param_page:
	kfree(p);
	return ret;
}

/*
 * nand_id_has_period - Check if an ID string has a given wraparound period
 * @id_data: the ID string
 * @arrlen: the length of the @id_data array
 * @period: the period of repitition
 *
 * Check if an ID string is repeated within a given sequence of bytes at
 * specific repetition interval period (e.g., {0x20,0x01,0x7F,0x20} has a
 * period of 3). This is a helper function for nand_id_len(). Returns non-zero
 * if the repetition has a period of @period; otherwise, returns zero.
 */
static int nand_id_has_period(u8 *id_data, int arrlen, int period)
{
	int i, j;
	for (i = 0; i < period; i++)
		for (j = i + period; j < arrlen; j += period)
			if (id_data[i] != id_data[j])
				return 0;
	return 1;
}

/*
 * nand_id_len - Get the length of an ID string returned by CMD_READID
 * @id_data: the ID string
 * @arrlen: the length of the @id_data array

 * Returns the length of the ID string, according to known wraparound/trailing
 * zero patterns. If no pattern exists, returns the length of the array.
 */
static int nand_id_len(u8 *id_data, int arrlen)
{
	int last_nonzero, period;

	/* Find last non-zero byte */
	for (last_nonzero = arrlen - 1; last_nonzero >= 0; last_nonzero--)
		if (id_data[last_nonzero])
			break;

	/* All zeros */
	if (last_nonzero < 0)
		return 0;

	/* Calculate wraparound period */
	for (period = 1; period < arrlen; period++)
		if (nand_id_has_period(id_data, arrlen, period))
			break;

	/* There's a repeated pattern */
	if (period < arrlen)
		return period;

	/* There are trailing zeros */
	if (last_nonzero < arrlen - 1)
		return last_nonzero + 1;

	/* No pattern detected */
	return arrlen;
}

/* Extract the bits of per cell from the 3rd byte of the extended ID */
static int nand_get_bits_per_cell(u8 cellinfo)
{
	int bits;

	bits = cellinfo & NAND_CI_CELLTYPE_MSK;
	bits >>= NAND_CI_CELLTYPE_SHIFT;
	return bits + 1;
}

/*
 * Many new NAND share similar device ID codes, which represent the size of the
 * chip. The rest of the parameters must be decoded according to generic or
 * manufacturer-specific "extended ID" decoding patterns.
 */
void nand_decode_ext_id(struct nand_chip *chip)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	int extid;
	u8 *id_data = chip->id.data;
	/* The 3rd id byte holds MLC / multichip data */
	chip->bits_per_cell = nand_get_bits_per_cell(id_data[2]);
	/* The 4th id byte is the important one */
	extid = id_data[3];

	/* Calc pagesize */
	mtd->writesize = 1024 << (extid & 0x03);
	extid >>= 2;
	/* Calc oobsize */
	mtd->oobsize = (8 << (extid & 0x01)) * (mtd->writesize >> 9);
	extid >>= 2;
	/* Calc blocksize. Blocksize is multiples of 64KiB */
	mtd->erasesize = (64 * 1024) << (extid & 0x03);
	extid >>= 2;
	/* Get buswidth information */
	if (extid & 0x1)
		chip->options |= NAND_BUSWIDTH_16;
}
EXPORT_SYMBOL_GPL(nand_decode_ext_id);

/*
 * Old devices have chip data hardcoded in the device ID table. nand_decode_id
 * decodes a matching ID table entry and assigns the MTD size parameters for
 * the chip.
 */
static void nand_decode_id(struct nand_chip *chip, struct nand_flash_dev *type)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	mtd->erasesize = type->erasesize;
	mtd->writesize = type->pagesize;
	mtd->oobsize = mtd->writesize / 32;

	/* All legacy ID NAND are small-page, SLC */
	chip->bits_per_cell = 1;
}

/*
 * Set the bad block marker/indicator (BBM/BBI) patterns according to some
 * heuristic patterns using various detected parameters (e.g., manufacturer,
 * page size, cell-type information).
 */
static void nand_decode_bbm_options(struct nand_chip *chip)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	/* Set the bad block position */
	if (mtd->writesize > 512 || (chip->options & NAND_BUSWIDTH_16))
		chip->badblockpos = NAND_LARGE_BADBLOCK_POS;
	else
		chip->badblockpos = NAND_SMALL_BADBLOCK_POS;
}

static inline bool is_full_id_nand(struct nand_flash_dev *type)
{
	return type->id_len;
}

static bool find_full_id_nand(struct nand_chip *chip,
			      struct nand_flash_dev *type)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	u8 *id_data = chip->id.data;

	if (!strncmp(type->id, id_data, type->id_len)) {
		mtd->writesize = type->pagesize;
		mtd->erasesize = type->erasesize;
		mtd->oobsize = type->oobsize;

		chip->bits_per_cell = nand_get_bits_per_cell(id_data[2]);
		chip->chipsize = (uint64_t)type->chipsize << 20;
		chip->options |= type->options;
		chip->ecc_strength_ds = NAND_ECC_STRENGTH(type);
		chip->ecc_step_ds = NAND_ECC_STEP(type);
		chip->onfi_timing_mode_default =
					type->onfi_timing_mode_default;

		chip->parameters.model = kstrdup(type->name, GFP_KERNEL);
		if (!chip->parameters.model)
			return false;

		return true;
	}
	return false;
}

/*
 * Manufacturer detection. Only used when the NAND is not ONFI or JEDEC
 * compliant and does not have a full-id or legacy-id entry in the nand_ids
 * table.
 */
static void nand_manufacturer_detect(struct nand_chip *chip)
{
	/*
	 * Try manufacturer detection if available and use
	 * nand_decode_ext_id() otherwise.
	 */
	if (chip->manufacturer.desc && chip->manufacturer.desc->ops &&
	    chip->manufacturer.desc->ops->detect) {
		/* The 3rd id byte holds MLC / multichip data */
		chip->bits_per_cell = nand_get_bits_per_cell(chip->id.data[2]);
		chip->manufacturer.desc->ops->detect(chip);
	} else {
		nand_decode_ext_id(chip);
	}
}

/*
 * Manufacturer initialization. This function is called for all NANDs including
 * ONFI and JEDEC compliant ones.
 * Manufacturer drivers should put all their specific initialization code in
 * their ->init() hook.
 */
static int nand_manufacturer_init(struct nand_chip *chip)
{
	if (!chip->manufacturer.desc || !chip->manufacturer.desc->ops ||
	    !chip->manufacturer.desc->ops->init)
		return 0;

	return chip->manufacturer.desc->ops->init(chip);
}

/*
 * Manufacturer cleanup. This function is called for all NANDs including
 * ONFI and JEDEC compliant ones.
 * Manufacturer drivers should put all their specific cleanup code in their
 * ->cleanup() hook.
 */
static void nand_manufacturer_cleanup(struct nand_chip *chip)
{
	/* Release manufacturer private data */
	if (chip->manufacturer.desc && chip->manufacturer.desc->ops &&
	    chip->manufacturer.desc->ops->cleanup)
		chip->manufacturer.desc->ops->cleanup(chip);
}

/*
 * Get the flash and manufacturer id and lookup if the type is supported.
 */
static int nand_detect(struct nand_chip *chip, struct nand_flash_dev *type)
{
	const struct nand_manufacturer *manufacturer;
	struct mtd_info *mtd = nand_to_mtd(chip);
	int busw, ret;
	u8 *id_data = chip->id.data;
	u8 maf_id, dev_id;

	/*
	 * Reset the chip, required by some chips (e.g. Micron MT29FxGxxxxx)
	 * after power-up.
	 */
	ret = nand_reset(chip, 0);
	if (ret)
		return ret;

	/* Select the device */
	chip->select_chip(mtd, 0);

	/* Send the command for reading device ID */
	ret = nand_readid_op(chip, 0, id_data, 2);
	if (ret)
		return ret;

	/* Read manufacturer and device IDs */
	maf_id = id_data[0];
	dev_id = id_data[1];

	/*
	 * Try again to make sure, as some systems the bus-hold or other
	 * interface concerns can cause random data which looks like a
	 * possibly credible NAND flash to appear. If the two results do
	 * not match, ignore the device completely.
	 */

	/* Read entire ID string */
	ret = nand_readid_op(chip, 0, id_data, sizeof(chip->id.data));
	if (ret)
		return ret;

	if (id_data[0] != maf_id || id_data[1] != dev_id) {
		pr_info("second ID read did not match %02x,%02x against %02x,%02x\n",
			maf_id, dev_id, id_data[0], id_data[1]);
		return -ENODEV;
	}

	chip->id.len = nand_id_len(id_data, ARRAY_SIZE(chip->id.data));

	/* Try to identify manufacturer */
	manufacturer = nand_get_manufacturer(maf_id);
	chip->manufacturer.desc = manufacturer;

	if (!type)
		type = nand_flash_ids;

	/*
	 * Save the NAND_BUSWIDTH_16 flag before letting auto-detection logic
	 * override it.
	 * This is required to make sure initial NAND bus width set by the
	 * NAND controller driver is coherent with the real NAND bus width
	 * (extracted by auto-detection code).
	 */
	busw = chip->options & NAND_BUSWIDTH_16;

	/*
	 * The flag is only set (never cleared), reset it to its default value
	 * before starting auto-detection.
	 */
	chip->options &= ~NAND_BUSWIDTH_16;

	for (; type->name != NULL; type++) {
		if (is_full_id_nand(type)) {
			if (find_full_id_nand(chip, type))
				goto ident_done;
		} else if (dev_id == type->dev_id) {
			break;
		}
	}

	if (!type->name || !type->pagesize) {
		/* Check if the chip is ONFI compliant */
		ret = nand_flash_detect_onfi(chip);
		if (ret < 0)
			return ret;
		else if (ret)
			goto ident_done;

		/* Check if the chip is JEDEC compliant */
		ret = nand_flash_detect_jedec(chip);
		if (ret < 0)
			return ret;
		else if (ret)
			goto ident_done;
	}

	if (!type->name)
		return -ENODEV;

	chip->parameters.model = kstrdup(type->name, GFP_KERNEL);
	if (!chip->parameters.model)
		return -ENOMEM;

	chip->chipsize = (uint64_t)type->chipsize << 20;

	if (!type->pagesize)
		nand_manufacturer_detect(chip);
	else
		nand_decode_id(chip, type);

	/* Get chip options */
	chip->options |= type->options;

ident_done:
	if (!mtd->name)
		mtd->name = chip->parameters.model;

	if (chip->options & NAND_BUSWIDTH_AUTO) {
		WARN_ON(busw & NAND_BUSWIDTH_16);
		nand_set_defaults(chip);
	} else if (busw != (chip->options & NAND_BUSWIDTH_16)) {
		/*
		 * Check, if buswidth is correct. Hardware drivers should set
		 * chip correct!
		 */
		pr_info("device found, Manufacturer ID: 0x%02x, Chip ID: 0x%02x\n",
			maf_id, dev_id);
		pr_info("%s %s\n", nand_manufacturer_name(manufacturer),
			mtd->name);
		pr_warn("bus width %d instead of %d bits\n", busw ? 16 : 8,
			(chip->options & NAND_BUSWIDTH_16) ? 16 : 8);
		ret = -EINVAL;

		goto free_detect_allocation;
	}

	nand_decode_bbm_options(chip);

	/* Calculate the address shift from the page size */
	chip->page_shift = ffs(mtd->writesize) - 1;
	/* Convert chipsize to number of pages per chip -1 */
	chip->pagemask = (chip->chipsize >> chip->page_shift) - 1;

	chip->bbt_erase_shift = chip->phys_erase_shift =
		ffs(mtd->erasesize) - 1;
	if (chip->chipsize & 0xffffffff)
		chip->chip_shift = ffs((unsigned)chip->chipsize) - 1;
	else {
		chip->chip_shift = ffs((unsigned)(chip->chipsize >> 32));
		chip->chip_shift += 32 - 1;
	}

	if (chip->chip_shift - chip->page_shift > 16)
		chip->options |= NAND_ROW_ADDR_3;

	chip->badblockbits = 8;
	chip->erase = single_erase;

	/* Do not replace user supplied command function! */
	if (mtd->writesize > 512 && chip->cmdfunc == nand_command)
		chip->cmdfunc = nand_command_lp;

	pr_info("device found, Manufacturer ID: 0x%02x, Chip ID: 0x%02x\n",
		maf_id, dev_id);
	pr_info("%s %s\n", nand_manufacturer_name(manufacturer),
		chip->parameters.model);
	pr_info("%d MiB, %s, erase size: %d KiB, page size: %d, OOB size: %d\n",
		(int)(chip->chipsize >> 20), nand_is_slc(chip) ? "SLC" : "MLC",
		mtd->erasesize >> 10, mtd->writesize, mtd->oobsize);
	return 0;

free_detect_allocation:
	kfree(chip->parameters.model);

	return ret;
}

static const char * const nand_ecc_modes[] = {
	[NAND_ECC_NONE]		= "none",
	[NAND_ECC_SOFT]		= "soft",
	[NAND_ECC_HW]		= "hw",
	[NAND_ECC_HW_SYNDROME]	= "hw_syndrome",
	[NAND_ECC_HW_OOB_FIRST]	= "hw_oob_first",
	[NAND_ECC_ON_DIE]	= "on-die",
};

static int of_get_nand_ecc_mode(struct device_node *np)
{
	const char *pm;
	int err, i;

	err = of_property_read_string(np, "nand-ecc-mode", &pm);
	if (err < 0)
		return err;

	for (i = 0; i < ARRAY_SIZE(nand_ecc_modes); i++)
		if (!strcasecmp(pm, nand_ecc_modes[i]))
			return i;

	/*
	 * For backward compatibility we support few obsoleted values that don't
	 * have their mappings into nand_ecc_modes_t anymore (they were merged
	 * with other enums).
	 */
	if (!strcasecmp(pm, "soft_bch"))
		return NAND_ECC_SOFT;

	return -ENODEV;
}

static const char * const nand_ecc_algos[] = {
	[NAND_ECC_HAMMING]	= "hamming",
	[NAND_ECC_BCH]		= "bch",
	[NAND_ECC_RS]		= "rs",
};

static int of_get_nand_ecc_algo(struct device_node *np)
{
	const char *pm;
	int err, i;

	err = of_property_read_string(np, "nand-ecc-algo", &pm);
	if (!err) {
		for (i = NAND_ECC_HAMMING; i < ARRAY_SIZE(nand_ecc_algos); i++)
			if (!strcasecmp(pm, nand_ecc_algos[i]))
				return i;
		return -ENODEV;
	}

	/*
	 * For backward compatibility we also read "nand-ecc-mode" checking
	 * for some obsoleted values that were specifying ECC algorithm.
	 */
	err = of_property_read_string(np, "nand-ecc-mode", &pm);
	if (err < 0)
		return err;

	if (!strcasecmp(pm, "soft"))
		return NAND_ECC_HAMMING;
	else if (!strcasecmp(pm, "soft_bch"))
		return NAND_ECC_BCH;

	return -ENODEV;
}

static int of_get_nand_ecc_step_size(struct device_node *np)
{
	int ret;
	u32 val;

	ret = of_property_read_u32(np, "nand-ecc-step-size", &val);
	return ret ? ret : val;
}

static int of_get_nand_ecc_strength(struct device_node *np)
{
	int ret;
	u32 val;

	ret = of_property_read_u32(np, "nand-ecc-strength", &val);
	return ret ? ret : val;
}

static int of_get_nand_bus_width(struct device_node *np)
{
	u32 val;

	if (of_property_read_u32(np, "nand-bus-width", &val))
		return 8;

	switch (val) {
	case 8:
	case 16:
		return val;
	default:
		return -EIO;
	}
}

static bool of_get_nand_on_flash_bbt(struct device_node *np)
{
	return of_property_read_bool(np, "nand-on-flash-bbt");
}

static int nand_dt_init(struct nand_chip *chip)
{
	struct device_node *dn = nand_get_flash_node(chip);
	int ecc_mode, ecc_algo, ecc_strength, ecc_step;

	if (!dn)
		return 0;

	if (of_get_nand_bus_width(dn) == 16)
		chip->options |= NAND_BUSWIDTH_16;

	if (of_property_read_bool(dn, "nand-is-boot-medium"))
		chip->options |= NAND_IS_BOOT_MEDIUM;

	if (of_get_nand_on_flash_bbt(dn))
		chip->bbt_options |= NAND_BBT_USE_FLASH;

	ecc_mode = of_get_nand_ecc_mode(dn);
	ecc_algo = of_get_nand_ecc_algo(dn);
	ecc_strength = of_get_nand_ecc_strength(dn);
	ecc_step = of_get_nand_ecc_step_size(dn);

	if (ecc_mode >= 0)
		chip->ecc.mode = ecc_mode;

	if (ecc_algo >= 0)
		chip->ecc.algo = ecc_algo;

	if (ecc_strength >= 0)
		chip->ecc.strength = ecc_strength;

	if (ecc_step > 0)
		chip->ecc.size = ecc_step;

	if (of_property_read_bool(dn, "nand-ecc-maximize"))
		chip->ecc.options |= NAND_ECC_MAXIMIZE;

	return 0;
}

/**
 * nand_scan_ident - Scan for the NAND device
 * @mtd: MTD device structure
 * @maxchips: number of chips to scan for
 * @table: alternative NAND ID table
 *
 * This is the first phase of the normal nand_scan() function. It reads the
 * flash ID and sets up MTD fields accordingly.
 *
 * This helper used to be called directly from controller drivers that needed
 * to tweak some ECC-related parameters before nand_scan_tail(). This separation
 * prevented dynamic allocations during this phase which was unconvenient and
 * as been banned for the benefit of the ->init_ecc()/cleanup_ecc() hooks.
 */
static int nand_scan_ident(struct mtd_info *mtd, int maxchips,
			   struct nand_flash_dev *table)
{
	int i, nand_maf_id, nand_dev_id;
	struct nand_chip *chip = mtd_to_nand(mtd);
	int ret;

	/* Enforce the right timings for reset/detection */
	onfi_fill_data_interface(chip, NAND_SDR_IFACE, 0);

	ret = nand_dt_init(chip);
	if (ret)
		return ret;

	if (!mtd->name && mtd->dev.parent)
		mtd->name = dev_name(mtd->dev.parent);

	/*
	 * ->cmdfunc() is legacy and will only be used if ->exec_op() is not
	 * populated.
	 */
	if (!chip->exec_op) {
		/*
		 * Default functions assigned for ->cmdfunc() and
		 * ->select_chip() both expect ->cmd_ctrl() to be populated.
		 */
		if ((!chip->cmdfunc || !chip->select_chip) && !chip->cmd_ctrl) {
			pr_err("->cmd_ctrl() should be provided\n");
			return -EINVAL;
		}
	}

	/* Set the default functions */
	nand_set_defaults(chip);

	/* Read the flash type */
	ret = nand_detect(chip, table);
	if (ret) {
		if (!(chip->options & NAND_SCAN_SILENT_NODEV))
			pr_warn("No NAND device found\n");
		chip->select_chip(mtd, -1);
		return ret;
	}

	nand_maf_id = chip->id.data[0];
	nand_dev_id = chip->id.data[1];

	chip->select_chip(mtd, -1);

	/* Check for a chip array */
	for (i = 1; i < maxchips; i++) {
		u8 id[2];

		/* See comment in nand_get_flash_type for reset */
		nand_reset(chip, i);

		chip->select_chip(mtd, i);
		/* Send the command for reading device ID */
		nand_readid_op(chip, 0, id, sizeof(id));
		/* Read manufacturer and device IDs */
		if (nand_maf_id != id[0] || nand_dev_id != id[1]) {
			chip->select_chip(mtd, -1);
			break;
		}
		chip->select_chip(mtd, -1);
	}
	if (i > 1)
		pr_info("%d chips detected\n", i);

	/* Store the number of chips and calc total size for mtd */
	chip->numchips = i;
	mtd->size = i * chip->chipsize;

	return 0;
}

static void nand_scan_ident_cleanup(struct nand_chip *chip)
{
	kfree(chip->parameters.model);
	kfree(chip->parameters.onfi);
}

static int nand_set_ecc_soft_ops(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct nand_ecc_ctrl *ecc = &chip->ecc;

	if (WARN_ON(ecc->mode != NAND_ECC_SOFT))
		return -EINVAL;

	switch (ecc->algo) {
	case NAND_ECC_HAMMING:
		ecc->calculate = nand_calculate_ecc;
		ecc->correct = nand_correct_data;
		ecc->read_page = nand_read_page_swecc;
		ecc->read_subpage = nand_read_subpage;
		ecc->write_page = nand_write_page_swecc;
		ecc->read_page_raw = nand_read_page_raw;
		ecc->write_page_raw = nand_write_page_raw;
		ecc->read_oob = nand_read_oob_std;
		ecc->write_oob = nand_write_oob_std;
		if (!ecc->size)
			ecc->size = 256;
		ecc->bytes = 3;
		ecc->strength = 1;
		return 0;
	case NAND_ECC_BCH:
		if (!mtd_nand_has_bch()) {
			WARN(1, "CONFIG_MTD_NAND_ECC_BCH not enabled\n");
			return -EINVAL;
		}
		ecc->calculate = nand_bch_calculate_ecc;
		ecc->correct = nand_bch_correct_data;
		ecc->read_page = nand_read_page_swecc;
		ecc->read_subpage = nand_read_subpage;
		ecc->write_page = nand_write_page_swecc;
		ecc->read_page_raw = nand_read_page_raw;
		ecc->write_page_raw = nand_write_page_raw;
		ecc->read_oob = nand_read_oob_std;
		ecc->write_oob = nand_write_oob_std;

		/*
		* Board driver should supply ecc.size and ecc.strength
		* values to select how many bits are correctable.
		* Otherwise, default to 4 bits for large page devices.
		*/
		if (!ecc->size && (mtd->oobsize >= 64)) {
			ecc->size = 512;
			ecc->strength = 4;
		}

		/*
		 * if no ecc placement scheme was provided pickup the default
		 * large page one.
		 */
		if (!mtd->ooblayout) {
			/* handle large page devices only */
			if (mtd->oobsize < 64) {
				WARN(1, "OOB layout is required when using software BCH on small pages\n");
				return -EINVAL;
			}

			mtd_set_ooblayout(mtd, &nand_ooblayout_lp_ops);

		}

		/*
		 * We can only maximize ECC config when the default layout is
		 * used, otherwise we don't know how many bytes can really be
		 * used.
		 */
		if (mtd->ooblayout == &nand_ooblayout_lp_ops &&
		    ecc->options & NAND_ECC_MAXIMIZE) {
			int steps, bytes;

			/* Always prefer 1k blocks over 512bytes ones */
			ecc->size = 1024;
			steps = mtd->writesize / ecc->size;

			/* Reserve 2 bytes for the BBM */
			bytes = (mtd->oobsize - 2) / steps;
			ecc->strength = bytes * 8 / fls(8 * ecc->size);
		}

		/* See nand_bch_init() for details. */
		ecc->bytes = 0;
		ecc->priv = nand_bch_init(mtd);
		if (!ecc->priv) {
			WARN(1, "BCH ECC initialization failed!\n");
			return -EINVAL;
		}
		return 0;
	default:
		WARN(1, "Unsupported ECC algorithm!\n");
		return -EINVAL;
	}
}

/**
 * nand_check_ecc_caps - check the sanity of preset ECC settings
 * @chip: nand chip info structure
 * @caps: ECC caps info structure
 * @oobavail: OOB size that the ECC engine can use
 *
 * When ECC step size and strength are already set, check if they are supported
 * by the controller and the calculated ECC bytes fit within the chip's OOB.
 * On success, the calculated ECC bytes is set.
 */
static int
nand_check_ecc_caps(struct nand_chip *chip,
		    const struct nand_ecc_caps *caps, int oobavail)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	const struct nand_ecc_step_info *stepinfo;
	int preset_step = chip->ecc.size;
	int preset_strength = chip->ecc.strength;
	int ecc_bytes, nsteps = mtd->writesize / preset_step;
	int i, j;

	for (i = 0; i < caps->nstepinfos; i++) {
		stepinfo = &caps->stepinfos[i];

		if (stepinfo->stepsize != preset_step)
			continue;

		for (j = 0; j < stepinfo->nstrengths; j++) {
			if (stepinfo->strengths[j] != preset_strength)
				continue;

			ecc_bytes = caps->calc_ecc_bytes(preset_step,
							 preset_strength);
			if (WARN_ON_ONCE(ecc_bytes < 0))
				return ecc_bytes;

			if (ecc_bytes * nsteps > oobavail) {
				pr_err("ECC (step, strength) = (%d, %d) does not fit in OOB",
				       preset_step, preset_strength);
				return -ENOSPC;
			}

			chip->ecc.bytes = ecc_bytes;

			return 0;
		}
	}

	pr_err("ECC (step, strength) = (%d, %d) not supported on this controller",
	       preset_step, preset_strength);

	return -ENOTSUPP;
}

/**
 * nand_match_ecc_req - meet the chip's requirement with least ECC bytes
 * @chip: nand chip info structure
 * @caps: ECC engine caps info structure
 * @oobavail: OOB size that the ECC engine can use
 *
 * If a chip's ECC requirement is provided, try to meet it with the least
 * number of ECC bytes (i.e. with the largest number of OOB-free bytes).
 * On success, the chosen ECC settings are set.
 */
static int
nand_match_ecc_req(struct nand_chip *chip,
		   const struct nand_ecc_caps *caps, int oobavail)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	const struct nand_ecc_step_info *stepinfo;
	int req_step = chip->ecc_step_ds;
	int req_strength = chip->ecc_strength_ds;
	int req_corr, step_size, strength, nsteps, ecc_bytes, ecc_bytes_total;
	int best_step, best_strength, best_ecc_bytes;
	int best_ecc_bytes_total = INT_MAX;
	int i, j;

	/* No information provided by the NAND chip */
	if (!req_step || !req_strength)
		return -ENOTSUPP;

	/* number of correctable bits the chip requires in a page */
	req_corr = mtd->writesize / req_step * req_strength;

	for (i = 0; i < caps->nstepinfos; i++) {
		stepinfo = &caps->stepinfos[i];
		step_size = stepinfo->stepsize;

		for (j = 0; j < stepinfo->nstrengths; j++) {
			strength = stepinfo->strengths[j];

			/*
			 * If both step size and strength are smaller than the
			 * chip's requirement, it is not easy to compare the
			 * resulted reliability.
			 */
			if (step_size < req_step && strength < req_strength)
				continue;

			if (mtd->writesize % step_size)
				continue;

			nsteps = mtd->writesize / step_size;

			ecc_bytes = caps->calc_ecc_bytes(step_size, strength);
			if (WARN_ON_ONCE(ecc_bytes < 0))
				continue;
			ecc_bytes_total = ecc_bytes * nsteps;

			if (ecc_bytes_total > oobavail ||
			    strength * nsteps < req_corr)
				continue;

			/*
			 * We assume the best is to meet the chip's requrement
			 * with the least number of ECC bytes.
			 */
			if (ecc_bytes_total < best_ecc_bytes_total) {
				best_ecc_bytes_total = ecc_bytes_total;
				best_step = step_size;
				best_strength = strength;
				best_ecc_bytes = ecc_bytes;
			}
		}
	}

	if (best_ecc_bytes_total == INT_MAX)
		return -ENOTSUPP;

	chip->ecc.size = best_step;
	chip->ecc.strength = best_strength;
	chip->ecc.bytes = best_ecc_bytes;

	return 0;
}

/**
 * nand_maximize_ecc - choose the max ECC strength available
 * @chip: nand chip info structure
 * @caps: ECC engine caps info structure
 * @oobavail: OOB size that the ECC engine can use
 *
 * Choose the max ECC strength that is supported on the controller, and can fit
 * within the chip's OOB.  On success, the chosen ECC settings are set.
 */
static int
nand_maximize_ecc(struct nand_chip *chip,
		  const struct nand_ecc_caps *caps, int oobavail)
{
	struct mtd_info *mtd = nand_to_mtd(chip);
	const struct nand_ecc_step_info *stepinfo;
	int step_size, strength, nsteps, ecc_bytes, corr;
	int best_corr = 0;
	int best_step = 0;
	int best_strength, best_ecc_bytes;
	int i, j;

	for (i = 0; i < caps->nstepinfos; i++) {
		stepinfo = &caps->stepinfos[i];
		step_size = stepinfo->stepsize;

		/* If chip->ecc.size is already set, respect it */
		if (chip->ecc.size && step_size != chip->ecc.size)
			continue;

		for (j = 0; j < stepinfo->nstrengths; j++) {
			strength = stepinfo->strengths[j];

			if (mtd->writesize % step_size)
				continue;

			nsteps = mtd->writesize / step_size;

			ecc_bytes = caps->calc_ecc_bytes(step_size, strength);
			if (WARN_ON_ONCE(ecc_bytes < 0))
				continue;

			if (ecc_bytes * nsteps > oobavail)
				continue;

			corr = strength * nsteps;

			/*
			 * If the number of correctable bits is the same,
			 * bigger step_size has more reliability.
			 */
			if (corr > best_corr ||
			    (corr == best_corr && step_size > best_step)) {
				best_corr = corr;
				best_step = step_size;
				best_strength = strength;
				best_ecc_bytes = ecc_bytes;
			}
		}
	}

	if (!best_corr)
		return -ENOTSUPP;

	chip->ecc.size = best_step;
	chip->ecc.strength = best_strength;
	chip->ecc.bytes = best_ecc_bytes;

	return 0;
}

/**
 * nand_ecc_choose_conf - Set the ECC strength and ECC step size
 * @chip: nand chip info structure
 * @caps: ECC engine caps info structure
 * @oobavail: OOB size that the ECC engine can use
 *
 * Choose the ECC configuration according to following logic
 *
 * 1. If both ECC step size and ECC strength are already set (usually by DT)
 *    then check if it is supported by this controller.
 * 2. If NAND_ECC_MAXIMIZE is set, then select maximum ECC strength.
 * 3. Otherwise, try to match the ECC step size and ECC strength closest
 *    to the chip's requirement. If available OOB size can't fit the chip
 *    requirement then fallback to the maximum ECC step size and ECC strength.
 *
 * On success, the chosen ECC settings are set.
 */
int nand_ecc_choose_conf(struct nand_chip *chip,
			 const struct nand_ecc_caps *caps, int oobavail)
{
	struct mtd_info *mtd = nand_to_mtd(chip);

	if (WARN_ON(oobavail < 0 || oobavail > mtd->oobsize))
		return -EINVAL;

	if (chip->ecc.size && chip->ecc.strength)
		return nand_check_ecc_caps(chip, caps, oobavail);

	if (chip->ecc.options & NAND_ECC_MAXIMIZE)
		return nand_maximize_ecc(chip, caps, oobavail);

	if (!nand_match_ecc_req(chip, caps, oobavail))
		return 0;

	return nand_maximize_ecc(chip, caps, oobavail);
}
EXPORT_SYMBOL_GPL(nand_ecc_choose_conf);

/*
 * Check if the chip configuration meet the datasheet requirements.

 * If our configuration corrects A bits per B bytes and the minimum
 * required correction level is X bits per Y bytes, then we must ensure
 * both of the following are true:
 *
 * (1) A / B >= X / Y
 * (2) A >= X
 *
 * Requirement (1) ensures we can correct for the required bitflip density.
 * Requirement (2) ensures we can correct even when all bitflips are clumped
 * in the same sector.
 */
static bool nand_ecc_strength_good(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int corr, ds_corr;

	if (ecc->size == 0 || chip->ecc_step_ds == 0)
		/* Not enough information */
		return true;

	/*
	 * We get the number of corrected bits per page to compare
	 * the correction density.
	 */
	corr = (mtd->writesize * ecc->strength) / ecc->size;
	ds_corr = (mtd->writesize * chip->ecc_strength_ds) / chip->ecc_step_ds;

	return corr >= ds_corr && ecc->strength >= chip->ecc_strength_ds;
}

/**
 * nand_scan_tail - Scan for the NAND device
 * @mtd: MTD device structure
 *
 * This is the second phase of the normal nand_scan() function. It fills out
 * all the uninitialized function pointers with the defaults and scans for a
 * bad block table if appropriate.
 */
static int nand_scan_tail(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int ret, i;

	/* New bad blocks should be marked in OOB, flash-based BBT, or both */
	if (WARN_ON((chip->bbt_options & NAND_BBT_NO_OOB_BBM) &&
		   !(chip->bbt_options & NAND_BBT_USE_FLASH))) {
		return -EINVAL;
	}

	chip->data_buf = kmalloc(mtd->writesize + mtd->oobsize, GFP_KERNEL);
	if (!chip->data_buf)
		return -ENOMEM;

	/*
	 * FIXME: some NAND manufacturer drivers expect the first die to be
	 * selected when manufacturer->init() is called. They should be fixed
	 * to explictly select the relevant die when interacting with the NAND
	 * chip.
	 */
	chip->select_chip(mtd, 0);
	ret = nand_manufacturer_init(chip);
	chip->select_chip(mtd, -1);
	if (ret)
		goto err_free_buf;

	/* Set the internal oob buffer location, just after the page data */
	chip->oob_poi = chip->data_buf + mtd->writesize;

	/*
	 * If no default placement scheme is given, select an appropriate one.
	 */
	if (!mtd->ooblayout &&
	    !(ecc->mode == NAND_ECC_SOFT && ecc->algo == NAND_ECC_BCH)) {
		switch (mtd->oobsize) {
		case 8:
		case 16:
			mtd_set_ooblayout(mtd, &nand_ooblayout_sp_ops);
			break;
		case 64:
		case 128:
			mtd_set_ooblayout(mtd, &nand_ooblayout_lp_hamming_ops);
			break;
		default:
			/*
			 * Expose the whole OOB area to users if ECC_NONE
			 * is passed. We could do that for all kind of
			 * ->oobsize, but we must keep the old large/small
			 * page with ECC layout when ->oobsize <= 128 for
			 * compatibility reasons.
			 */
			if (ecc->mode == NAND_ECC_NONE) {
				mtd_set_ooblayout(mtd,
						&nand_ooblayout_lp_ops);
				break;
			}

			WARN(1, "No oob scheme defined for oobsize %d\n",
				mtd->oobsize);
			ret = -EINVAL;
			goto err_nand_manuf_cleanup;
		}
	}

	/*
	 * Check ECC mode, default to software if 3byte/512byte hardware ECC is
	 * selected and we have 256 byte pagesize fallback to software ECC
	 */

	switch (ecc->mode) {
	case NAND_ECC_HW_OOB_FIRST:
		/* Similar to NAND_ECC_HW, but a separate read_page handle */
		if (!ecc->calculate || !ecc->correct || !ecc->hwctl) {
			WARN(1, "No ECC functions supplied; hardware ECC not possible\n");
			ret = -EINVAL;
			goto err_nand_manuf_cleanup;
		}
		if (!ecc->read_page)
			ecc->read_page = nand_read_page_hwecc_oob_first;

	case NAND_ECC_HW:
		/* Use standard hwecc read page function? */
		if (!ecc->read_page)
			ecc->read_page = nand_read_page_hwecc;
		if (!ecc->write_page)
			ecc->write_page = nand_write_page_hwecc;
		if (!ecc->read_page_raw)
			ecc->read_page_raw = nand_read_page_raw;
		if (!ecc->write_page_raw)
			ecc->write_page_raw = nand_write_page_raw;
		if (!ecc->read_oob)
			ecc->read_oob = nand_read_oob_std;
		if (!ecc->write_oob)
			ecc->write_oob = nand_write_oob_std;
		if (!ecc->read_subpage)
			ecc->read_subpage = nand_read_subpage;
		if (!ecc->write_subpage && ecc->hwctl && ecc->calculate)
			ecc->write_subpage = nand_write_subpage_hwecc;

	case NAND_ECC_HW_SYNDROME:
		if ((!ecc->calculate || !ecc->correct || !ecc->hwctl) &&
		    (!ecc->read_page ||
		     ecc->read_page == nand_read_page_hwecc ||
		     !ecc->write_page ||
		     ecc->write_page == nand_write_page_hwecc)) {
			WARN(1, "No ECC functions supplied; hardware ECC not possible\n");
			ret = -EINVAL;
			goto err_nand_manuf_cleanup;
		}
		/* Use standard syndrome read/write page function? */
		if (!ecc->read_page)
			ecc->read_page = nand_read_page_syndrome;
		if (!ecc->write_page)
			ecc->write_page = nand_write_page_syndrome;
		if (!ecc->read_page_raw)
			ecc->read_page_raw = nand_read_page_raw_syndrome;
		if (!ecc->write_page_raw)
			ecc->write_page_raw = nand_write_page_raw_syndrome;
		if (!ecc->read_oob)
			ecc->read_oob = nand_read_oob_syndrome;
		if (!ecc->write_oob)
			ecc->write_oob = nand_write_oob_syndrome;

		if (mtd->writesize >= ecc->size) {
			if (!ecc->strength) {
				WARN(1, "Driver must set ecc.strength when using hardware ECC\n");
				ret = -EINVAL;
				goto err_nand_manuf_cleanup;
			}
			break;
		}
		pr_warn("%d byte HW ECC not possible on %d byte page size, fallback to SW ECC\n",
			ecc->size, mtd->writesize);
		ecc->mode = NAND_ECC_SOFT;
		ecc->algo = NAND_ECC_HAMMING;

	case NAND_ECC_SOFT:
		ret = nand_set_ecc_soft_ops(mtd);
		if (ret) {
			ret = -EINVAL;
			goto err_nand_manuf_cleanup;
		}
		break;

	case NAND_ECC_ON_DIE:
		if (!ecc->read_page || !ecc->write_page) {
			WARN(1, "No ECC functions supplied; on-die ECC not possible\n");
			ret = -EINVAL;
			goto err_nand_manuf_cleanup;
		}
		if (!ecc->read_oob)
			ecc->read_oob = nand_read_oob_std;
		if (!ecc->write_oob)
			ecc->write_oob = nand_write_oob_std;
		break;

	case NAND_ECC_NONE:
		pr_warn("NAND_ECC_NONE selected by board driver. This is not recommended!\n");
		ecc->read_page = nand_read_page_raw;
		ecc->write_page = nand_write_page_raw;
		ecc->read_oob = nand_read_oob_std;
		ecc->read_page_raw = nand_read_page_raw;
		ecc->write_page_raw = nand_write_page_raw;
		ecc->write_oob = nand_write_oob_std;
		ecc->size = mtd->writesize;
		ecc->bytes = 0;
		ecc->strength = 0;
		break;

	default:
		WARN(1, "Invalid NAND_ECC_MODE %d\n", ecc->mode);
		ret = -EINVAL;
		goto err_nand_manuf_cleanup;
	}

	if (ecc->correct || ecc->calculate) {
		ecc->calc_buf = kmalloc(mtd->oobsize, GFP_KERNEL);
		ecc->code_buf = kmalloc(mtd->oobsize, GFP_KERNEL);
		if (!ecc->calc_buf || !ecc->code_buf) {
			ret = -ENOMEM;
			goto err_nand_manuf_cleanup;
		}
	}

	/* For many systems, the standard OOB write also works for raw */
	if (!ecc->read_oob_raw)
		ecc->read_oob_raw = ecc->read_oob;
	if (!ecc->write_oob_raw)
		ecc->write_oob_raw = ecc->write_oob;

	/* propagate ecc info to mtd_info */
	mtd->ecc_strength = ecc->strength;
	mtd->ecc_step_size = ecc->size;

	/*
	 * Set the number of read / write steps for one page depending on ECC
	 * mode.
	 */
	ecc->steps = mtd->writesize / ecc->size;
	if (ecc->steps * ecc->size != mtd->writesize) {
		WARN(1, "Invalid ECC parameters\n");
		ret = -EINVAL;
		goto err_nand_manuf_cleanup;
	}
	ecc->total = ecc->steps * ecc->bytes;
	if (ecc->total > mtd->oobsize) {
		WARN(1, "Total number of ECC bytes exceeded oobsize\n");
		ret = -EINVAL;
		goto err_nand_manuf_cleanup;
	}

	/*
	 * The number of bytes available for a client to place data into
	 * the out of band area.
	 */
	ret = mtd_ooblayout_count_freebytes(mtd);
	if (ret < 0)
		ret = 0;

	mtd->oobavail = ret;

	/* ECC sanity check: warn if it's too weak */
	if (!nand_ecc_strength_good(mtd))
		pr_warn("WARNING: %s: the ECC used on your system is too weak compared to the one required by the NAND chip\n",
			mtd->name);

	/* Allow subpage writes up to ecc.steps. Not possible for MLC flash */
	if (!(chip->options & NAND_NO_SUBPAGE_WRITE) && nand_is_slc(chip)) {
		switch (ecc->steps) {
		case 2:
			mtd->subpage_sft = 1;
			break;
		case 4:
		case 8:
		case 16:
			mtd->subpage_sft = 2;
			break;
		}
	}
	chip->subpagesize = mtd->writesize >> mtd->subpage_sft;

	/* Initialize state */
	chip->state = FL_READY;

	/* Invalidate the pagebuffer reference */
	chip->pagebuf = -1;

	/* Large page NAND with SOFT_ECC should support subpage reads */
	switch (ecc->mode) {
	case NAND_ECC_SOFT:
		if (chip->page_shift > 9)
			chip->options |= NAND_SUBPAGE_READ;
		break;

	default:
		break;
	}

	/* Fill in remaining MTD driver data */
	mtd->type = nand_is_slc(chip) ? MTD_NANDFLASH : MTD_MLCNANDFLASH;
	mtd->flags = (chip->options & NAND_ROM) ? MTD_CAP_ROM :
						MTD_CAP_NANDFLASH;
	mtd->_erase = nand_erase;
	mtd->_point = NULL;
	mtd->_unpoint = NULL;
	mtd->_panic_write = panic_nand_write;
	mtd->_read_oob = nand_read_oob;
	mtd->_write_oob = nand_write_oob;
	mtd->_sync = nand_sync;
	mtd->_lock = NULL;
	mtd->_unlock = NULL;
	mtd->_suspend = nand_suspend;
	mtd->_resume = nand_resume;
	mtd->_reboot = nand_shutdown;
	mtd->_block_isreserved = nand_block_isreserved;
	mtd->_block_isbad = nand_block_isbad;
	mtd->_block_markbad = nand_block_markbad;
	mtd->_max_bad_blocks = nand_max_bad_blocks;
	mtd->writebufsize = mtd->writesize;

	/*
	 * Initialize bitflip_threshold to its default prior scan_bbt() call.
	 * scan_bbt() might invoke mtd_read(), thus bitflip_threshold must be
	 * properly set.
	 */
	if (!mtd->bitflip_threshold)
		mtd->bitflip_threshold = DIV_ROUND_UP(mtd->ecc_strength * 3, 4);

	/* Initialize the ->data_interface field. */
	ret = nand_init_data_interface(chip);
	if (ret)
		goto err_nand_manuf_cleanup;

	/* Enter fastest possible mode on all dies. */
	for (i = 0; i < chip->numchips; i++) {
		ret = nand_setup_data_interface(chip, i);
		if (ret)
			goto err_nand_manuf_cleanup;
	}

	/* Check, if we should skip the bad block table scan */
	if (chip->options & NAND_SKIP_BBTSCAN)
		return 0;

	/* Build bad block table */
	ret = nand_create_bbt(chip);
	if (ret)
		goto err_nand_manuf_cleanup;

	return 0;


err_nand_manuf_cleanup:
	nand_manufacturer_cleanup(chip);

err_free_buf:
	kfree(chip->data_buf);
	kfree(ecc->code_buf);
	kfree(ecc->calc_buf);

	return ret;
}

static int nand_attach(struct nand_chip *chip)
{
	if (chip->controller->ops && chip->controller->ops->attach_chip)
		return chip->controller->ops->attach_chip(chip);

	return 0;
}

static void nand_detach(struct nand_chip *chip)
{
	if (chip->controller->ops && chip->controller->ops->detach_chip)
		chip->controller->ops->detach_chip(chip);
}

/**
 * nand_scan_with_ids - [NAND Interface] Scan for the NAND device
 * @mtd: MTD device structure
 * @maxchips: number of chips to scan for. @nand_scan_ident() will not be run if
 *	      this parameter is zero (useful for specific drivers that must
 *	      handle this part of the process themselves, e.g docg4).
 * @ids: optional flash IDs table
 *
 * This fills out all the uninitialized function pointers with the defaults.
 * The flash ID is read and the mtd/chip structures are filled with the
 * appropriate values.
 */
int nand_scan_with_ids(struct mtd_info *mtd, int maxchips,
		       struct nand_flash_dev *ids)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	int ret;

	if (maxchips) {
		ret = nand_scan_ident(mtd, maxchips, ids);
		if (ret)
			return ret;
	}

	ret = nand_attach(chip);
	if (ret)
		goto cleanup_ident;

	ret = nand_scan_tail(mtd);
	if (ret)
		goto detach_chip;

	return 0;

detach_chip:
	nand_detach(chip);
cleanup_ident:
	nand_scan_ident_cleanup(chip);

	return ret;
}
EXPORT_SYMBOL(nand_scan_with_ids);

/**
 * nand_cleanup - [NAND Interface] Free resources held by the NAND device
 * @chip: NAND chip object
 */
void nand_cleanup(struct nand_chip *chip)
{
	if (chip->ecc.mode == NAND_ECC_SOFT &&
	    chip->ecc.algo == NAND_ECC_BCH)
		nand_bch_free((struct nand_bch_control *)chip->ecc.priv);

	/* Free bad block table memory */
	kfree(chip->bbt);
	kfree(chip->data_buf);
	kfree(chip->ecc.code_buf);
	kfree(chip->ecc.calc_buf);

	/* Free bad block descriptor memory */
	if (chip->badblock_pattern && chip->badblock_pattern->options
			& NAND_BBT_DYNAMICSTRUCT)
		kfree(chip->badblock_pattern);

	/* Free manufacturer priv data. */
	nand_manufacturer_cleanup(chip);

	/* Free controller specific allocations after chip identification */
	nand_detach(chip);

	/* Free identification phase allocations */
	nand_scan_ident_cleanup(chip);
}

EXPORT_SYMBOL_GPL(nand_cleanup);

/**
 * nand_release - [NAND Interface] Unregister the MTD device and free resources
 *		  held by the NAND device
 * @mtd: MTD device structure
 */
void nand_release(struct mtd_info *mtd)
{
	mtd_device_unregister(mtd);
	nand_cleanup(mtd_to_nand(mtd));
}
EXPORT_SYMBOL_GPL(nand_release);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
MODULE_AUTHOR("Thomas Gleixner <tglx@linutronix.de>");
MODULE_DESCRIPTION("Generic NAND flash driver code");