drivers/rtc/rtc-ds1511.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * An rtc driver for the Dallas DS1511
  *
  * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
  * Copyright (C) 2007 Andrew Sharp <andy.sharp@lsi.com>
  *
  * Real time clock driver for the Dallas 1511 chip, which also
  * contains a watchdog timer.  There is a tiny amount of code that
  * platform code could use to mess with the watchdog device a little
  * bit, but not a full watchdog driver.
  */

 #include <linux/bcd.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/gfp.h>
 #include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/rtc.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
 #include <linux/module.h>

 enum ds1511reg {
 	DS1511_SEC = 0x0,
 	DS1511_MIN = 0x1,
 	DS1511_HOUR = 0x2,
 	DS1511_DOW = 0x3,
 	DS1511_DOM = 0x4,
 	DS1511_MONTH = 0x5,
 	DS1511_YEAR = 0x6,
 	DS1511_CENTURY = 0x7,
 	DS1511_AM1_SEC = 0x8,
 	DS1511_AM2_MIN = 0x9,
 	DS1511_AM3_HOUR = 0xa,
 	DS1511_AM4_DATE = 0xb,
 	DS1511_WD_MSEC = 0xc,
 	DS1511_WD_SEC = 0xd,
 	DS1511_CONTROL_A = 0xe,
 	DS1511_CONTROL_B = 0xf,
 	DS1511_RAMADDR_LSB = 0x10,
 	DS1511_RAMDATA = 0x13
 };

 #define DS1511_BLF1	0x80
 #define DS1511_BLF2	0x40
 #define DS1511_PRS	0x20
 #define DS1511_PAB	0x10
 #define DS1511_TDF	0x08
 #define DS1511_KSF	0x04
 #define DS1511_WDF	0x02
 #define DS1511_IRQF	0x01
 #define DS1511_TE	0x80
 #define DS1511_CS	0x40
 #define DS1511_BME	0x20
 #define DS1511_TPE	0x10
 #define DS1511_TIE	0x08
 #define DS1511_KIE	0x04
 #define DS1511_WDE	0x02
 #define DS1511_WDS	0x01
 #define DS1511_RAM_MAX	0x100

 #define RTC_CMD		DS1511_CONTROL_B
 #define RTC_CMD1	DS1511_CONTROL_A

 #define RTC_ALARM_SEC	DS1511_AM1_SEC
 #define RTC_ALARM_MIN	DS1511_AM2_MIN
 #define RTC_ALARM_HOUR	DS1511_AM3_HOUR
 #define RTC_ALARM_DATE	DS1511_AM4_DATE

 #define RTC_SEC		DS1511_SEC
 #define RTC_MIN		DS1511_MIN
 #define RTC_HOUR	DS1511_HOUR
 #define RTC_DOW		DS1511_DOW
 #define RTC_DOM		DS1511_DOM
 #define RTC_MON		DS1511_MONTH
 #define RTC_YEAR	DS1511_YEAR
 #define RTC_CENTURY	DS1511_CENTURY

 #define RTC_TIE	DS1511_TIE
 #define RTC_TE	DS1511_TE

 struct rtc_plat_data {
 	struct rtc_device *rtc;
 	void __iomem *ioaddr;		/* virtual base address */
 	int irq;
 	unsigned int irqen;
 	int alrm_sec;
 	int alrm_min;
 	int alrm_hour;
 	int alrm_mday;
 	spinlock_t lock;
 };

 static DEFINE_SPINLOCK(ds1511_lock);

 static __iomem char *ds1511_base;
 static u32 reg_spacing = 1;

 static noinline void
 rtc_write(uint8_t val, uint32_t reg)
 {
 	writeb(val, ds1511_base + (reg * reg_spacing));
 }

 static inline void
 rtc_write_alarm(uint8_t val, enum ds1511reg reg)
 {
 	rtc_write((val | 0x80), reg);
 }

 static noinline uint8_t
 rtc_read(enum ds1511reg reg)
 {
 	return readb(ds1511_base + (reg * reg_spacing));
 }

 static inline void
 rtc_disable_update(void)
 {
 	rtc_write((rtc_read(RTC_CMD) & ~RTC_TE), RTC_CMD);
 }

 static void
 rtc_enable_update(void)
 {
 	rtc_write((rtc_read(RTC_CMD) | RTC_TE), RTC_CMD);
 }

 /*
  * #define DS1511_WDOG_RESET_SUPPORT
  *
  * Uncomment this if you want to use these routines in
  * some platform code.
  */
 #ifdef DS1511_WDOG_RESET_SUPPORT
 /*
  * just enough code to set the watchdog timer so that it
  * will reboot the system
  */
 void
 ds1511_wdog_set(unsigned long deciseconds)
 {
 	/*
 	 * the wdog timer can take 99.99 seconds
 	 */
 	deciseconds %= 10000;
 	/*
 	 * set the wdog values in the wdog registers
 	 */
 	rtc_write(bin2bcd(deciseconds % 100), DS1511_WD_MSEC);
 	rtc_write(bin2bcd(deciseconds / 100), DS1511_WD_SEC);
 	/*
 	 * set wdog enable and wdog 'steering' bit to issue a reset
 	 */
 	rtc_write(rtc_read(RTC_CMD) | DS1511_WDE | DS1511_WDS, RTC_CMD);
 }

 void
 ds1511_wdog_disable(void)
 {
 	/*
 	 * clear wdog enable and wdog 'steering' bits
 	 */
 	rtc_write(rtc_read(RTC_CMD) & ~(DS1511_WDE | DS1511_WDS), RTC_CMD);
 	/*
 	 * clear the wdog counter
 	 */
 	rtc_write(0, DS1511_WD_MSEC);
 	rtc_write(0, DS1511_WD_SEC);
 }
 #endif

 /*
  * set the rtc chip's idea of the time.
  * stupidly, some callers call with year unmolested;
  * and some call with  year = year - 1900.  thanks.
  */
 static int ds1511_rtc_set_time(struct device *dev, struct rtc_time *rtc_tm)
 {
 	u8 mon, day, dow, hrs, min, sec, yrs, cen;
 	unsigned long flags;

 	/*
 	 * won't have to change this for a while
 	 */
 	if (rtc_tm->tm_year < 1900)
 		rtc_tm->tm_year += 1900;

 	if (rtc_tm->tm_year < 1970)
 		return -EINVAL;

 	yrs = rtc_tm->tm_year % 100;
 	cen = rtc_tm->tm_year / 100;
 	mon = rtc_tm->tm_mon + 1;   /* tm_mon starts at zero */
 	day = rtc_tm->tm_mday;
 	dow = rtc_tm->tm_wday & 0x7; /* automatic BCD */
 	hrs = rtc_tm->tm_hour;
 	min = rtc_tm->tm_min;
 	sec = rtc_tm->tm_sec;

 	if ((mon > 12) || (day == 0))
 		return -EINVAL;

 	if (day > rtc_month_days(rtc_tm->tm_mon, rtc_tm->tm_year))
 		return -EINVAL;

 	if ((hrs >= 24) || (min >= 60) || (sec >= 60))
 		return -EINVAL;

 	/*
 	 * each register is a different number of valid bits
 	 */
 	sec = bin2bcd(sec) & 0x7f;
 	min = bin2bcd(min) & 0x7f;
 	hrs = bin2bcd(hrs) & 0x3f;
 	day = bin2bcd(day) & 0x3f;
 	mon = bin2bcd(mon) & 0x1f;
 	yrs = bin2bcd(yrs) & 0xff;
 	cen = bin2bcd(cen) & 0xff;

 	spin_lock_irqsave(&ds1511_lock, flags);
 	rtc_disable_update();
 	rtc_write(cen, RTC_CENTURY);
 	rtc_write(yrs, RTC_YEAR);
 	rtc_write((rtc_read(RTC_MON) & 0xe0) | mon, RTC_MON);
 	rtc_write(day, RTC_DOM);
 	rtc_write(hrs, RTC_HOUR);
 	rtc_write(min, RTC_MIN);
 	rtc_write(sec, RTC_SEC);
 	rtc_write(dow, RTC_DOW);
 	rtc_enable_update();
 	spin_unlock_irqrestore(&ds1511_lock, flags);

 	return 0;
 }

 static int ds1511_rtc_read_time(struct device *dev, struct rtc_time *rtc_tm)
 {
 	unsigned int century;
 	unsigned long flags;

 	spin_lock_irqsave(&ds1511_lock, flags);
 	rtc_disable_update();

 	rtc_tm->tm_sec = rtc_read(RTC_SEC) & 0x7f;
 	rtc_tm->tm_min = rtc_read(RTC_MIN) & 0x7f;
 	rtc_tm->tm_hour = rtc_read(RTC_HOUR) & 0x3f;
 	rtc_tm->tm_mday = rtc_read(RTC_DOM) & 0x3f;
 	rtc_tm->tm_wday = rtc_read(RTC_DOW) & 0x7;
 	rtc_tm->tm_mon = rtc_read(RTC_MON) & 0x1f;
 	rtc_tm->tm_year = rtc_read(RTC_YEAR) & 0x7f;
 	century = rtc_read(RTC_CENTURY);

 	rtc_enable_update();
 	spin_unlock_irqrestore(&ds1511_lock, flags);

 	rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
 	rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
 	rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
 	rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
 	rtc_tm->tm_wday = bcd2bin(rtc_tm->tm_wday);
 	rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon);
 	rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);
 	century = bcd2bin(century) * 100;

 	/*
 	 * Account for differences between how the RTC uses the values
 	 * and how they are defined in a struct rtc_time;
 	 */
 	century += rtc_tm->tm_year;
 	rtc_tm->tm_year = century - 1900;

 	rtc_tm->tm_mon--;

 	return 0;
 }

 /*
  * write the alarm register settings
  *
  * we only have the use to interrupt every second, otherwise
  * known as the update interrupt, or the interrupt if the whole
  * date/hours/mins/secs matches.  the ds1511 has many more
  * permutations, but the kernel doesn't.
  */
 static void
 ds1511_rtc_update_alarm(struct rtc_plat_data *pdata)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&pdata->lock, flags);
 	rtc_write(pdata->alrm_mday < 0 || (pdata->irqen & RTC_UF) ?
 	       0x80 : bin2bcd(pdata->alrm_mday) & 0x3f,
 	       RTC_ALARM_DATE);
 	rtc_write(pdata->alrm_hour < 0 || (pdata->irqen & RTC_UF) ?
 	       0x80 : bin2bcd(pdata->alrm_hour) & 0x3f,
 	       RTC_ALARM_HOUR);
 	rtc_write(pdata->alrm_min < 0 || (pdata->irqen & RTC_UF) ?
 	       0x80 : bin2bcd(pdata->alrm_min) & 0x7f,
 	       RTC_ALARM_MIN);
 	rtc_write(pdata->alrm_sec < 0 || (pdata->irqen & RTC_UF) ?
 	       0x80 : bin2bcd(pdata->alrm_sec) & 0x7f,
 	       RTC_ALARM_SEC);
 	rtc_write(rtc_read(RTC_CMD) | (pdata->irqen ? RTC_TIE : 0), RTC_CMD);
 	rtc_read(RTC_CMD1);	/* clear interrupts */
 	spin_unlock_irqrestore(&pdata->lock, flags);
 }

 static int
 ds1511_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct rtc_plat_data *pdata = dev_get_drvdata(dev);

 	if (pdata->irq <= 0)
 		return -EINVAL;

 	pdata->alrm_mday = alrm->time.tm_mday;
 	pdata->alrm_hour = alrm->time.tm_hour;
 	pdata->alrm_min = alrm->time.tm_min;
 	pdata->alrm_sec = alrm->time.tm_sec;
 	if (alrm->enabled)
 		pdata->irqen |= RTC_AF;

 	ds1511_rtc_update_alarm(pdata);
 	return 0;
 }

 static int
 ds1511_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct rtc_plat_data *pdata = dev_get_drvdata(dev);

 	if (pdata->irq <= 0)
 		return -EINVAL;

 	alrm->time.tm_mday = pdata->alrm_mday < 0 ? 0 : pdata->alrm_mday;
 	alrm->time.tm_hour = pdata->alrm_hour < 0 ? 0 : pdata->alrm_hour;
 	alrm->time.tm_min = pdata->alrm_min < 0 ? 0 : pdata->alrm_min;
 	alrm->time.tm_sec = pdata->alrm_sec < 0 ? 0 : pdata->alrm_sec;
 	alrm->enabled = (pdata->irqen & RTC_AF) ? 1 : 0;
 	return 0;
 }

 static irqreturn_t
 ds1511_interrupt(int irq, void *dev_id)
 {
 	struct platform_device *pdev = dev_id;
 	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
 	unsigned long events = 0;

 	spin_lock(&pdata->lock);
 	/*
 	 * read and clear interrupt
 	 */
 	if (rtc_read(RTC_CMD1) & DS1511_IRQF) {
 		events = RTC_IRQF;
 		if (rtc_read(RTC_ALARM_SEC) & 0x80)
 			events |= RTC_UF;
 		else
 			events |= RTC_AF;
 		rtc_update_irq(pdata->rtc, 1, events);
 	}
 	spin_unlock(&pdata->lock);
 	return events ? IRQ_HANDLED : IRQ_NONE;
 }

 static int ds1511_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
 {
 	struct rtc_plat_data *pdata = dev_get_drvdata(dev);

 	if (pdata->irq <= 0)
 		return -EINVAL;
 	if (enabled)
 		pdata->irqen |= RTC_AF;
 	else
 		pdata->irqen &= ~RTC_AF;
 	ds1511_rtc_update_alarm(pdata);
 	return 0;
 }

 static const struct rtc_class_ops ds1511_rtc_ops = {
 	.read_time		= ds1511_rtc_read_time,
 	.set_time		= ds1511_rtc_set_time,
 	.read_alarm		= ds1511_rtc_read_alarm,
 	.set_alarm		= ds1511_rtc_set_alarm,
 	.alarm_irq_enable	= ds1511_rtc_alarm_irq_enable,
 };

 static int ds1511_nvram_read(void *priv, unsigned int pos, void *buf,
 			     size_t size)
 {
 	int i;

 	rtc_write(pos, DS1511_RAMADDR_LSB);
 	for (i = 0; i < size; i++)
 		*(char *)buf++ = rtc_read(DS1511_RAMDATA);

 	return 0;
 }

 static int ds1511_nvram_write(void *priv, unsigned int pos, void *buf,
 			      size_t size)
 {
 	int i;

 	rtc_write(pos, DS1511_RAMADDR_LSB);
 	for (i = 0; i < size; i++)
 		rtc_write(*(char *)buf++, DS1511_RAMDATA);

 	return 0;
 }

 static int ds1511_rtc_probe(struct platform_device *pdev)
 {
 	struct resource *res;
 	struct rtc_plat_data *pdata;
 	int ret = 0;
 	struct nvmem_config ds1511_nvmem_cfg = {
 		.name = "ds1511_nvram",
 		.word_size = 1,
 		.stride = 1,
 		.size = DS1511_RAM_MAX,
 		.reg_read = ds1511_nvram_read,
 		.reg_write = ds1511_nvram_write,
 		.priv = &pdev->dev,
 	};

 	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
 	if (!pdata)
 		return -ENOMEM;

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	ds1511_base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(ds1511_base))
 		return PTR_ERR(ds1511_base);
 	pdata->ioaddr = ds1511_base;
 	pdata->irq = platform_get_irq(pdev, 0);

 	/*
 	 * turn on the clock and the crystal, etc.
 	 */
 	rtc_write(DS1511_BME, RTC_CMD);
 	rtc_write(0, RTC_CMD1);
 	/*
 	 * clear the wdog counter
 	 */
 	rtc_write(0, DS1511_WD_MSEC);
 	rtc_write(0, DS1511_WD_SEC);
 	/*
 	 * start the clock
 	 */
 	rtc_enable_update();

 	/*
 	 * check for a dying bat-tree
 	 */
 	if (rtc_read(RTC_CMD1) & DS1511_BLF1)
 		dev_warn(&pdev->dev, "voltage-low detected.\n");

 	spin_lock_init(&pdata->lock);
 	platform_set_drvdata(pdev, pdata);

 	pdata->rtc = devm_rtc_allocate_device(&pdev->dev);
 	if (IS_ERR(pdata->rtc))
 		return PTR_ERR(pdata->rtc);

 	pdata->rtc->ops = &ds1511_rtc_ops;

 	pdata->rtc->nvram_old_abi = true;

 	ret = rtc_register_device(pdata->rtc);
 	if (ret)
 		return ret;

 	rtc_nvmem_register(pdata->rtc, &ds1511_nvmem_cfg);

 	/*
 	 * if the platform has an interrupt in mind for this device,
 	 * then by all means, set it
 	 */
 	if (pdata->irq > 0) {
 		rtc_read(RTC_CMD1);
 		if (devm_request_irq(&pdev->dev, pdata->irq, ds1511_interrupt,
 			IRQF_SHARED, pdev->name, pdev) < 0) {

 			dev_warn(&pdev->dev, "interrupt not available.\n");
 			pdata->irq = 0;
 		}
 	}

 	return 0;
 }

 /* work with hotplug and coldplug */
 MODULE_ALIAS("platform:ds1511");

 static struct platform_driver ds1511_rtc_driver = {
 	.probe		= ds1511_rtc_probe,
 	.driver		= {
 		.name	= "ds1511",
 	},
 };

 module_platform_driver(ds1511_rtc_driver);

 MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>");
 MODULE_DESCRIPTION("Dallas DS1511 RTC driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* An rtc driver for the Dallas DS1511
	*
	* Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
	* Copyright (C) 2007 Andrew Sharp <andy.sharp@lsi.com>
	*
	* Real time clock driver for the Dallas 1511 chip, which also
	* contains a watchdog timer. There is a tiny amount of code that
	* platform code could use to mess with the watchdog device a little
	* bit, but not a full watchdog driver.
	*/

	#include <linux/bcd.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/gfp.h>
	#include <linux/delay.h>
	#include <linux/interrupt.h>
	#include <linux/rtc.h>
	#include <linux/platform_device.h>
	#include <linux/io.h>
	#include <linux/module.h>

	enum ds1511reg {
	DS1511_SEC = 0x0,
	DS1511_MIN = 0x1,
	DS1511_HOUR = 0x2,
	DS1511_DOW = 0x3,
	DS1511_DOM = 0x4,
	DS1511_MONTH = 0x5,
	DS1511_YEAR = 0x6,
	DS1511_CENTURY = 0x7,
	DS1511_AM1_SEC = 0x8,
	DS1511_AM2_MIN = 0x9,
	DS1511_AM3_HOUR = 0xa,
	DS1511_AM4_DATE = 0xb,
	DS1511_WD_MSEC = 0xc,
	DS1511_WD_SEC = 0xd,
	DS1511_CONTROL_A = 0xe,
	DS1511_CONTROL_B = 0xf,
	DS1511_RAMADDR_LSB = 0x10,
	DS1511_RAMDATA = 0x13
	};

	#define DS1511_BLF1 0x80
	#define DS1511_BLF2 0x40
	#define DS1511_PRS 0x20
	#define DS1511_PAB 0x10
	#define DS1511_TDF 0x08
	#define DS1511_KSF 0x04
	#define DS1511_WDF 0x02
	#define DS1511_IRQF 0x01
	#define DS1511_TE 0x80
	#define DS1511_CS 0x40
	#define DS1511_BME 0x20
	#define DS1511_TPE 0x10
	#define DS1511_TIE 0x08
	#define DS1511_KIE 0x04
	#define DS1511_WDE 0x02
	#define DS1511_WDS 0x01
	#define DS1511_RAM_MAX 0x100

	#define RTC_CMD DS1511_CONTROL_B
	#define RTC_CMD1 DS1511_CONTROL_A

	#define RTC_ALARM_SEC DS1511_AM1_SEC
	#define RTC_ALARM_MIN DS1511_AM2_MIN
	#define RTC_ALARM_HOUR DS1511_AM3_HOUR
	#define RTC_ALARM_DATE DS1511_AM4_DATE

	#define RTC_SEC DS1511_SEC
	#define RTC_MIN DS1511_MIN
	#define RTC_HOUR DS1511_HOUR
	#define RTC_DOW DS1511_DOW
	#define RTC_DOM DS1511_DOM
	#define RTC_MON DS1511_MONTH
	#define RTC_YEAR DS1511_YEAR
	#define RTC_CENTURY DS1511_CENTURY

	#define RTC_TIE DS1511_TIE
	#define RTC_TE DS1511_TE

	struct rtc_plat_data {
	struct rtc_device *rtc;
	void __iomem ioaddr; / virtual base address */
	int irq;
	unsigned int irqen;
	int alrm_sec;
	int alrm_min;
	int alrm_hour;
	int alrm_mday;
	spinlock_t lock;
	};

	static DEFINE_SPINLOCK(ds1511_lock);

	static __iomem char *ds1511_base;
	static u32 reg_spacing = 1;

	static noinline void
	rtc_write(uint8_t val, uint32_t reg)
	{
	writeb(val, ds1511_base + (reg * reg_spacing));
	}

	static inline void
	rtc_write_alarm(uint8_t val, enum ds1511reg reg)
	{
	rtc_write((val \| 0x80), reg);
	}

	static noinline uint8_t
	rtc_read(enum ds1511reg reg)
	{
	return readb(ds1511_base + (reg * reg_spacing));
	}

	static inline void
	rtc_disable_update(void)
	{
	rtc_write((rtc_read(RTC_CMD) & ~RTC_TE), RTC_CMD);
	}

	static void
	rtc_enable_update(void)
	{
	rtc_write((rtc_read(RTC_CMD) \| RTC_TE), RTC_CMD);
	}

	/*
	* #define DS1511_WDOG_RESET_SUPPORT
	*
	* Uncomment this if you want to use these routines in
	* some platform code.
	*/
	#ifdef DS1511_WDOG_RESET_SUPPORT
	/*
	* just enough code to set the watchdog timer so that it
	* will reboot the system
	*/
	void
	ds1511_wdog_set(unsigned long deciseconds)
	{
	/*
	* the wdog timer can take 99.99 seconds
	*/
	deciseconds %= 10000;
	/*
	* set the wdog values in the wdog registers
	*/
	rtc_write(bin2bcd(deciseconds % 100), DS1511_WD_MSEC);
	rtc_write(bin2bcd(deciseconds / 100), DS1511_WD_SEC);
	/*
	* set wdog enable and wdog 'steering' bit to issue a reset
	*/
	rtc_write(rtc_read(RTC_CMD) \| DS1511_WDE \| DS1511_WDS, RTC_CMD);
	}

	void
	ds1511_wdog_disable(void)
	{
	/*
	* clear wdog enable and wdog 'steering' bits
	*/
	rtc_write(rtc_read(RTC_CMD) & ~(DS1511_WDE \| DS1511_WDS), RTC_CMD);
	/*
	* clear the wdog counter
	*/
	rtc_write(0, DS1511_WD_MSEC);
	rtc_write(0, DS1511_WD_SEC);
	}
	#endif

	/*
	* set the rtc chip's idea of the time.
	* stupidly, some callers call with year unmolested;
	* and some call with year = year - 1900. thanks.
	*/
	static int ds1511_rtc_set_time(struct device dev, struct rtc_time rtc_tm)
	{
	u8 mon, day, dow, hrs, min, sec, yrs, cen;
	unsigned long flags;

	/*
	* won't have to change this for a while
	*/
	if (rtc_tm->tm_year < 1900)
	rtc_tm->tm_year += 1900;

	if (rtc_tm->tm_year < 1970)
	return -EINVAL;

	yrs = rtc_tm->tm_year % 100;
	cen = rtc_tm->tm_year / 100;
	mon = rtc_tm->tm_mon + 1; /* tm_mon starts at zero */
	day = rtc_tm->tm_mday;
	dow = rtc_tm->tm_wday & 0x7; /* automatic BCD */
	hrs = rtc_tm->tm_hour;
	min = rtc_tm->tm_min;
	sec = rtc_tm->tm_sec;

	if ((mon > 12) \|\| (day == 0))
	return -EINVAL;

	if (day > rtc_month_days(rtc_tm->tm_mon, rtc_tm->tm_year))
	return -EINVAL;

	if ((hrs >= 24) \|\| (min >= 60) \|\| (sec >= 60))
	return -EINVAL;

	/*
	* each register is a different number of valid bits
	*/
	sec = bin2bcd(sec) & 0x7f;
	min = bin2bcd(min) & 0x7f;
	hrs = bin2bcd(hrs) & 0x3f;
	day = bin2bcd(day) & 0x3f;
	mon = bin2bcd(mon) & 0x1f;
	yrs = bin2bcd(yrs) & 0xff;
	cen = bin2bcd(cen) & 0xff;

	spin_lock_irqsave(&ds1511_lock, flags);
	rtc_disable_update();
	rtc_write(cen, RTC_CENTURY);
	rtc_write(yrs, RTC_YEAR);
	rtc_write((rtc_read(RTC_MON) & 0xe0) \| mon, RTC_MON);
	rtc_write(day, RTC_DOM);
	rtc_write(hrs, RTC_HOUR);
	rtc_write(min, RTC_MIN);
	rtc_write(sec, RTC_SEC);
	rtc_write(dow, RTC_DOW);
	rtc_enable_update();
	spin_unlock_irqrestore(&ds1511_lock, flags);

	return 0;
	}

	static int ds1511_rtc_read_time(struct device dev, struct rtc_time rtc_tm)
	{
	unsigned int century;
	unsigned long flags;

	spin_lock_irqsave(&ds1511_lock, flags);
	rtc_disable_update();

	rtc_tm->tm_sec = rtc_read(RTC_SEC) & 0x7f;
	rtc_tm->tm_min = rtc_read(RTC_MIN) & 0x7f;
	rtc_tm->tm_hour = rtc_read(RTC_HOUR) & 0x3f;
	rtc_tm->tm_mday = rtc_read(RTC_DOM) & 0x3f;
	rtc_tm->tm_wday = rtc_read(RTC_DOW) & 0x7;
	rtc_tm->tm_mon = rtc_read(RTC_MON) & 0x1f;
	rtc_tm->tm_year = rtc_read(RTC_YEAR) & 0x7f;
	century = rtc_read(RTC_CENTURY);

	rtc_enable_update();
	spin_unlock_irqrestore(&ds1511_lock, flags);

	rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
	rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
	rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
	rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
	rtc_tm->tm_wday = bcd2bin(rtc_tm->tm_wday);
	rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon);
	rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);
	century = bcd2bin(century) * 100;

	/*
	* Account for differences between how the RTC uses the values
	* and how they are defined in a struct rtc_time;
	*/
	century += rtc_tm->tm_year;
	rtc_tm->tm_year = century - 1900;

	rtc_tm->tm_mon--;

	return 0;
	}

	/*
	* write the alarm register settings
	*
	* we only have the use to interrupt every second, otherwise
	* known as the update interrupt, or the interrupt if the whole
	* date/hours/mins/secs matches. the ds1511 has many more
	* permutations, but the kernel doesn't.
	*/
	static void
	ds1511_rtc_update_alarm(struct rtc_plat_data *pdata)
	{
	unsigned long flags;

	spin_lock_irqsave(&pdata->lock, flags);
	rtc_write(pdata->alrm_mday < 0 \|\| (pdata->irqen & RTC_UF) ?
	0x80 : bin2bcd(pdata->alrm_mday) & 0x3f,
	RTC_ALARM_DATE);
	rtc_write(pdata->alrm_hour < 0 \|\| (pdata->irqen & RTC_UF) ?
	0x80 : bin2bcd(pdata->alrm_hour) & 0x3f,
	RTC_ALARM_HOUR);
	rtc_write(pdata->alrm_min < 0 \|\| (pdata->irqen & RTC_UF) ?
	0x80 : bin2bcd(pdata->alrm_min) & 0x7f,
	RTC_ALARM_MIN);
	rtc_write(pdata->alrm_sec < 0 \|\| (pdata->irqen & RTC_UF) ?
	0x80 : bin2bcd(pdata->alrm_sec) & 0x7f,
	RTC_ALARM_SEC);
	rtc_write(rtc_read(RTC_CMD) \| (pdata->irqen ? RTC_TIE : 0), RTC_CMD);
	rtc_read(RTC_CMD1); /* clear interrupts */
	spin_unlock_irqrestore(&pdata->lock, flags);
	}

	static int
	ds1511_rtc_set_alarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct rtc_plat_data *pdata = dev_get_drvdata(dev);

	if (pdata->irq <= 0)
	return -EINVAL;

	pdata->alrm_mday = alrm->time.tm_mday;
	pdata->alrm_hour = alrm->time.tm_hour;
	pdata->alrm_min = alrm->time.tm_min;
	pdata->alrm_sec = alrm->time.tm_sec;
	if (alrm->enabled)
	pdata->irqen \|= RTC_AF;

	ds1511_rtc_update_alarm(pdata);
	return 0;
	}

	static int
	ds1511_rtc_read_alarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct rtc_plat_data *pdata = dev_get_drvdata(dev);

	if (pdata->irq <= 0)
	return -EINVAL;

	alrm->time.tm_mday = pdata->alrm_mday < 0 ? 0 : pdata->alrm_mday;
	alrm->time.tm_hour = pdata->alrm_hour < 0 ? 0 : pdata->alrm_hour;
	alrm->time.tm_min = pdata->alrm_min < 0 ? 0 : pdata->alrm_min;
	alrm->time.tm_sec = pdata->alrm_sec < 0 ? 0 : pdata->alrm_sec;
	alrm->enabled = (pdata->irqen & RTC_AF) ? 1 : 0;
	return 0;
	}

	static irqreturn_t
	ds1511_interrupt(int irq, void *dev_id)
	{
	struct platform_device *pdev = dev_id;
	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
	unsigned long events = 0;

	spin_lock(&pdata->lock);
	/*
	* read and clear interrupt
	*/
	if (rtc_read(RTC_CMD1) & DS1511_IRQF) {
	events = RTC_IRQF;
	if (rtc_read(RTC_ALARM_SEC) & 0x80)
	events \|= RTC_UF;
	else
	events \|= RTC_AF;
	rtc_update_irq(pdata->rtc, 1, events);
	}
	spin_unlock(&pdata->lock);
	return events ? IRQ_HANDLED : IRQ_NONE;
	}

	static int ds1511_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
	{
	struct rtc_plat_data *pdata = dev_get_drvdata(dev);

	if (pdata->irq <= 0)
	return -EINVAL;
	if (enabled)
	pdata->irqen \|= RTC_AF;
	else
	pdata->irqen &= ~RTC_AF;
	ds1511_rtc_update_alarm(pdata);
	return 0;
	}

	static const struct rtc_class_ops ds1511_rtc_ops = {
	.read_time = ds1511_rtc_read_time,
	.set_time = ds1511_rtc_set_time,
	.read_alarm = ds1511_rtc_read_alarm,
	.set_alarm = ds1511_rtc_set_alarm,
	.alarm_irq_enable = ds1511_rtc_alarm_irq_enable,
	};

	static int ds1511_nvram_read(void priv, unsigned int pos, void buf,
	size_t size)
	{
	int i;

	rtc_write(pos, DS1511_RAMADDR_LSB);
	for (i = 0; i < size; i++)
	(char )buf++ = rtc_read(DS1511_RAMDATA);

	return 0;
	}

	static int ds1511_nvram_write(void priv, unsigned int pos, void buf,
	size_t size)
	{
	int i;

	rtc_write(pos, DS1511_RAMADDR_LSB);
	for (i = 0; i < size; i++)
	rtc_write((char )buf++, DS1511_RAMDATA);

	return 0;
	}

	static int ds1511_rtc_probe(struct platform_device *pdev)
	{
	struct resource *res;
	struct rtc_plat_data *pdata;
	int ret = 0;
	struct nvmem_config ds1511_nvmem_cfg = {
	.name = "ds1511_nvram",
	.word_size = 1,
	.stride = 1,
	.size = DS1511_RAM_MAX,
	.reg_read = ds1511_nvram_read,
	.reg_write = ds1511_nvram_write,
	.priv = &pdev->dev,
	};

	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
	if (!pdata)
	return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	ds1511_base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(ds1511_base))
	return PTR_ERR(ds1511_base);
	pdata->ioaddr = ds1511_base;
	pdata->irq = platform_get_irq(pdev, 0);

	/*
	* turn on the clock and the crystal, etc.
	*/
	rtc_write(DS1511_BME, RTC_CMD);
	rtc_write(0, RTC_CMD1);
	/*
	* clear the wdog counter
	*/
	rtc_write(0, DS1511_WD_MSEC);
	rtc_write(0, DS1511_WD_SEC);
	/*
	* start the clock
	*/
	rtc_enable_update();

	/*
	* check for a dying bat-tree
	*/
	if (rtc_read(RTC_CMD1) & DS1511_BLF1)
	dev_warn(&pdev->dev, "voltage-low detected.\n");

	spin_lock_init(&pdata->lock);
	platform_set_drvdata(pdev, pdata);

	pdata->rtc = devm_rtc_allocate_device(&pdev->dev);
	if (IS_ERR(pdata->rtc))
	return PTR_ERR(pdata->rtc);

	pdata->rtc->ops = &ds1511_rtc_ops;

	pdata->rtc->nvram_old_abi = true;

	ret = rtc_register_device(pdata->rtc);
	if (ret)
	return ret;

	rtc_nvmem_register(pdata->rtc, &ds1511_nvmem_cfg);

	/*
	* if the platform has an interrupt in mind for this device,
	* then by all means, set it
	*/
	if (pdata->irq > 0) {
	rtc_read(RTC_CMD1);
	if (devm_request_irq(&pdev->dev, pdata->irq, ds1511_interrupt,
	IRQF_SHARED, pdev->name, pdev) < 0) {

	dev_warn(&pdev->dev, "interrupt not available.\n");
	pdata->irq = 0;
	}
	}

	return 0;
	}

	/* work with hotplug and coldplug */
	MODULE_ALIAS("platform:ds1511");

	static struct platform_driver ds1511_rtc_driver = {
	.probe = ds1511_rtc_probe,
	.driver = {
	.name = "ds1511",
	},
	};

	module_platform_driver(ds1511_rtc_driver);

	MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>");
	MODULE_DESCRIPTION("Dallas DS1511 RTC driver");
	MODULE_LICENSE("GPL");