/*
 * drivers/rtc/rtc-pcf85363.c
 *
 * Driver for NXP PCF85363 real-time clock.
 *
 * Copyright (C) 2017 Eric Nelson
 *
 * 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.
 *
 * Based loosely on rtc-8583 by Russell King, Wolfram Sang and Juergen Beisert
 */
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/slab.h>
#include <linux/rtc.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/bcd.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/regmap.h>

/*
 * Date/Time registers
 */
#define DT_100THS	0x00
#define DT_SECS		0x01
#define DT_MINUTES	0x02
#define DT_HOURS	0x03
#define DT_DAYS		0x04
#define DT_WEEKDAYS	0x05
#define DT_MONTHS	0x06
#define DT_YEARS	0x07

/*
 * Alarm registers
 */
#define DT_SECOND_ALM1	0x08
#define DT_MINUTE_ALM1	0x09
#define DT_HOUR_ALM1	0x0a
#define DT_DAY_ALM1	0x0b
#define DT_MONTH_ALM1	0x0c
#define DT_MINUTE_ALM2	0x0d
#define DT_HOUR_ALM2	0x0e
#define DT_WEEKDAY_ALM2	0x0f
#define DT_ALARM_EN	0x10

/*
 * Time stamp registers
 */
#define DT_TIMESTAMP1	0x11
#define DT_TIMESTAMP2	0x17
#define DT_TIMESTAMP3	0x1d
#define DT_TS_MODE	0x23

/*
 * control registers
 */
#define CTRL_OFFSET	0x24
#define CTRL_OSCILLATOR	0x25
#define CTRL_BATTERY	0x26
#define CTRL_PIN_IO	0x27
#define CTRL_FUNCTION	0x28
#define CTRL_INTA_EN	0x29
#define CTRL_INTB_EN	0x2a
#define CTRL_FLAGS	0x2b
#define CTRL_RAMBYTE	0x2c
#define CTRL_WDOG	0x2d
#define CTRL_STOP_EN	0x2e
#define CTRL_RESETS	0x2f
#define CTRL_RAM	0x40

#define NVRAM_SIZE	0x40

static struct i2c_driver pcf85363_driver;

struct pcf85363 {
	struct device		*dev;
	struct rtc_device	*rtc;
	struct nvmem_config	nvmem_cfg;
	struct regmap		*regmap;
};

static int pcf85363_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct pcf85363 *pcf85363 = dev_get_drvdata(dev);
	unsigned char buf[DT_YEARS + 1];
	int ret, len = sizeof(buf);

	/* read the RTC date and time registers all at once */
	ret = regmap_bulk_read(pcf85363->regmap, DT_100THS, buf, len);
	if (ret) {
		dev_err(dev, "%s: error %d\n", __func__, ret);
		return ret;
	}

	tm->tm_year = bcd2bin(buf[DT_YEARS]);
	/* adjust for 1900 base of rtc_time */
	tm->tm_year += 100;

	tm->tm_wday = buf[DT_WEEKDAYS] & 7;
	buf[DT_SECS] &= 0x7F;
	tm->tm_sec = bcd2bin(buf[DT_SECS]);
	buf[DT_MINUTES] &= 0x7F;
	tm->tm_min = bcd2bin(buf[DT_MINUTES]);
	tm->tm_hour = bcd2bin(buf[DT_HOURS]);
	tm->tm_mday = bcd2bin(buf[DT_DAYS]);
	tm->tm_mon = bcd2bin(buf[DT_MONTHS]) - 1;

	return 0;
}

static int pcf85363_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct pcf85363 *pcf85363 = dev_get_drvdata(dev);
	unsigned char buf[DT_YEARS + 1];
	int len = sizeof(buf);

	buf[DT_100THS] = 0;
	buf[DT_SECS] = bin2bcd(tm->tm_sec);
	buf[DT_MINUTES] = bin2bcd(tm->tm_min);
	buf[DT_HOURS] = bin2bcd(tm->tm_hour);
	buf[DT_DAYS] = bin2bcd(tm->tm_mday);
	buf[DT_WEEKDAYS] = tm->tm_wday;
	buf[DT_MONTHS] = bin2bcd(tm->tm_mon + 1);
	buf[DT_YEARS] = bin2bcd(tm->tm_year % 100);

	return regmap_bulk_write(pcf85363->regmap, DT_100THS,
				 buf, len);
}

static const struct rtc_class_ops rtc_ops = {
	.read_time	= pcf85363_rtc_read_time,
	.set_time	= pcf85363_rtc_set_time,
};

static int pcf85363_nvram_read(void *priv, unsigned int offset, void *val,
			       size_t bytes)
{
	struct pcf85363 *pcf85363 = priv;

	return regmap_bulk_read(pcf85363->regmap, CTRL_RAM + offset,
				val, bytes);
}

static int pcf85363_nvram_write(void *priv, unsigned int offset, void *val,
				size_t bytes)
{
	struct pcf85363 *pcf85363 = priv;

	return regmap_bulk_write(pcf85363->regmap, CTRL_RAM + offset,
				 val, bytes);
}

static const struct regmap_config regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
};

static int pcf85363_probe(struct i2c_client *client,
			  const struct i2c_device_id *id)
{
	struct pcf85363 *pcf85363;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
		return -ENODEV;

	pcf85363 = devm_kzalloc(&client->dev, sizeof(struct pcf85363),
				GFP_KERNEL);
	if (!pcf85363)
		return -ENOMEM;

	pcf85363->regmap = devm_regmap_init_i2c(client, &regmap_config);
	if (IS_ERR(pcf85363->regmap)) {
		dev_err(&client->dev, "regmap allocation failed\n");
		return PTR_ERR(pcf85363->regmap);
	}

	pcf85363->dev = &client->dev;
	i2c_set_clientdata(client, pcf85363);

	pcf85363->rtc = devm_rtc_allocate_device(pcf85363->dev);
	if (IS_ERR(pcf85363->rtc))
		return PTR_ERR(pcf85363->rtc);

	pcf85363->nvmem_cfg.name = "pcf85363-";
	pcf85363->nvmem_cfg.word_size = 1;
	pcf85363->nvmem_cfg.stride = 1;
	pcf85363->nvmem_cfg.size = NVRAM_SIZE;
	pcf85363->nvmem_cfg.reg_read = pcf85363_nvram_read;
	pcf85363->nvmem_cfg.reg_write = pcf85363_nvram_write;
	pcf85363->nvmem_cfg.priv = pcf85363;
	pcf85363->rtc->nvmem_config = &pcf85363->nvmem_cfg;
	pcf85363->rtc->ops = &rtc_ops;

	return rtc_register_device(pcf85363->rtc);
}

static const struct of_device_id dev_ids[] = {
	{ .compatible = "nxp,pcf85363" },
	{}
};
MODULE_DEVICE_TABLE(of, dev_ids);

static struct i2c_driver pcf85363_driver = {
	.driver	= {
		.name	= "pcf85363",
		.of_match_table = of_match_ptr(dev_ids),
	},
	.probe	= pcf85363_probe,
};

module_i2c_driver(pcf85363_driver);

MODULE_AUTHOR("Eric Nelson");
MODULE_DESCRIPTION("pcf85363 I2C RTC driver");
MODULE_LICENSE("GPL");