drivers/rtc/rtc-stk17ta8.c - linux/torvalds/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * A RTC driver for the Simtek STK17TA8
  *
  * By Thomas Hommel <thomas.hommel@ge.com>
  *
  * Based on the DS1553 driver from
  * Atsushi Nemoto <anemo@mba.ocn.ne.jp>
  */

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

 #define RTC_REG_SIZE		0x20000
 #define RTC_OFFSET		0x1fff0

 #define RTC_FLAGS		(RTC_OFFSET + 0)
 #define RTC_CENTURY		(RTC_OFFSET + 1)
 #define RTC_SECONDS_ALARM	(RTC_OFFSET + 2)
 #define RTC_MINUTES_ALARM	(RTC_OFFSET + 3)
 #define RTC_HOURS_ALARM		(RTC_OFFSET + 4)
 #define RTC_DATE_ALARM		(RTC_OFFSET + 5)
 #define RTC_INTERRUPTS		(RTC_OFFSET + 6)
 #define RTC_WATCHDOG		(RTC_OFFSET + 7)
 #define RTC_CALIBRATION		(RTC_OFFSET + 8)
 #define RTC_SECONDS		(RTC_OFFSET + 9)
 #define RTC_MINUTES		(RTC_OFFSET + 10)
 #define RTC_HOURS		(RTC_OFFSET + 11)
 #define RTC_DAY			(RTC_OFFSET + 12)
 #define RTC_DATE		(RTC_OFFSET + 13)
 #define RTC_MONTH		(RTC_OFFSET + 14)
 #define RTC_YEAR		(RTC_OFFSET + 15)

 #define RTC_SECONDS_MASK	0x7f
 #define RTC_DAY_MASK		0x07
 #define RTC_CAL_MASK		0x3f

 /* Bits in the Calibration register */
 #define RTC_STOP		0x80

 /* Bits in the Flags register */
 #define RTC_FLAGS_AF		0x40
 #define RTC_FLAGS_PF		0x20
 #define RTC_WRITE		0x02
 #define RTC_READ		0x01

 /* Bits in the Interrupts register */
 #define RTC_INTS_AIE		0x40

 struct rtc_plat_data {
 	struct rtc_device *rtc;
 	void __iomem *ioaddr;
 	unsigned long last_jiffies;
 	int irq;
 	unsigned int irqen;
 	int alrm_sec;
 	int alrm_min;
 	int alrm_hour;
 	int alrm_mday;
 	spinlock_t lock;
 };

 static int stk17ta8_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
 	void __iomem *ioaddr = pdata->ioaddr;
 	u8 flags;

 	flags = readb(pdata->ioaddr + RTC_FLAGS);
 	writeb(flags | RTC_WRITE, pdata->ioaddr + RTC_FLAGS);

 	writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
 	writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
 	writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
 	writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
 	writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
 	writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
 	writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);
 	writeb(bin2bcd((tm->tm_year + 1900) / 100), ioaddr + RTC_CENTURY);

 	writeb(flags & ~RTC_WRITE, pdata->ioaddr + RTC_FLAGS);
 	return 0;
 }

 static int stk17ta8_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
 	void __iomem *ioaddr = pdata->ioaddr;
 	unsigned int year, month, day, hour, minute, second, week;
 	unsigned int century;
 	u8 flags;

 	/* give enough time to update RTC in case of continuous read */
 	if (pdata->last_jiffies == jiffies)
 		msleep(1);
 	pdata->last_jiffies = jiffies;

 	flags = readb(pdata->ioaddr + RTC_FLAGS);
 	writeb(flags | RTC_READ, ioaddr + RTC_FLAGS);
 	second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
 	minute = readb(ioaddr + RTC_MINUTES);
 	hour = readb(ioaddr + RTC_HOURS);
 	day = readb(ioaddr + RTC_DATE);
 	week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
 	month = readb(ioaddr + RTC_MONTH);
 	year = readb(ioaddr + RTC_YEAR);
 	century = readb(ioaddr + RTC_CENTURY);
 	writeb(flags & ~RTC_READ, ioaddr + RTC_FLAGS);
 	tm->tm_sec = bcd2bin(second);
 	tm->tm_min = bcd2bin(minute);
 	tm->tm_hour = bcd2bin(hour);
 	tm->tm_mday = bcd2bin(day);
 	tm->tm_wday = bcd2bin(week);
 	tm->tm_mon = bcd2bin(month) - 1;
 	/* year is 1900 + tm->tm_year */
 	tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;

 	return 0;
 }

 static void stk17ta8_rtc_update_alarm(struct rtc_plat_data *pdata)
 {
 	void __iomem *ioaddr = pdata->ioaddr;
 	unsigned long irqflags;
 	u8 flags;

 	spin_lock_irqsave(&pdata->lock, irqflags);

 	flags = readb(ioaddr + RTC_FLAGS);
 	writeb(flags | RTC_WRITE, ioaddr + RTC_FLAGS);

 	writeb(pdata->alrm_mday < 0 || (pdata->irqen & RTC_UF) ?
 	       0x80 : bin2bcd(pdata->alrm_mday),
 	       ioaddr + RTC_DATE_ALARM);
 	writeb(pdata->alrm_hour < 0 || (pdata->irqen & RTC_UF) ?
 	       0x80 : bin2bcd(pdata->alrm_hour),
 	       ioaddr + RTC_HOURS_ALARM);
 	writeb(pdata->alrm_min < 0 || (pdata->irqen & RTC_UF) ?
 	       0x80 : bin2bcd(pdata->alrm_min),
 	       ioaddr + RTC_MINUTES_ALARM);
 	writeb(pdata->alrm_sec < 0 || (pdata->irqen & RTC_UF) ?
 	       0x80 : bin2bcd(pdata->alrm_sec),
 	       ioaddr + RTC_SECONDS_ALARM);
 	writeb(pdata->irqen ? RTC_INTS_AIE : 0, ioaddr + RTC_INTERRUPTS);
 	readb(ioaddr + RTC_FLAGS);	/* clear interrupts */
 	writeb(flags & ~RTC_WRITE, ioaddr + RTC_FLAGS);
 	spin_unlock_irqrestore(&pdata->lock, irqflags);
 }

 static int stk17ta8_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;
 	stk17ta8_rtc_update_alarm(pdata);
 	return 0;
 }

 static int stk17ta8_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 stk17ta8_rtc_interrupt(int irq, void *dev_id)
 {
 	struct platform_device *pdev = dev_id;
 	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
 	void __iomem *ioaddr = pdata->ioaddr;
 	unsigned long events = 0;

 	spin_lock(&pdata->lock);
 	/* read and clear interrupt */
 	if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_AF) {
 		events = RTC_IRQF;
 		if (readb(ioaddr + RTC_SECONDS_ALARM) & 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 stk17ta8_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;
 	stk17ta8_rtc_update_alarm(pdata);
 	return 0;
 }

 static const struct rtc_class_ops stk17ta8_rtc_ops = {
 	.read_time		= stk17ta8_rtc_read_time,
 	.set_time		= stk17ta8_rtc_set_time,
 	.read_alarm		= stk17ta8_rtc_read_alarm,
 	.set_alarm		= stk17ta8_rtc_set_alarm,
 	.alarm_irq_enable	= stk17ta8_rtc_alarm_irq_enable,
 };

 static int stk17ta8_nvram_read(void *priv, unsigned int pos, void *val,
 			       size_t bytes)
 {
 	struct rtc_plat_data *pdata = priv;
 	void __iomem *ioaddr = pdata->ioaddr;
 	u8 *buf = val;

 	for (; bytes; bytes--)
 		*buf++ = readb(ioaddr + pos++);
 	return 0;
 }

 static int stk17ta8_nvram_write(void *priv, unsigned int pos, void *val,
 				size_t bytes)
 {
 	struct rtc_plat_data *pdata = priv;
 	void __iomem *ioaddr = pdata->ioaddr;
 	u8 *buf = val;

 	for (; bytes; bytes--)
 		writeb(*buf++, ioaddr + pos++);
 	return 0;
 }

 static int stk17ta8_rtc_probe(struct platform_device *pdev)
 {
 	struct resource *res;
 	unsigned int cal;
 	unsigned int flags;
 	struct rtc_plat_data *pdata;
 	void __iomem *ioaddr;
 	int ret = 0;
 	struct nvmem_config nvmem_cfg = {
 		.name = "stk17ta8_nvram",
 		.word_size = 1,
 		.stride = 1,
 		.size = RTC_OFFSET,
 		.reg_read = stk17ta8_nvram_read,
 		.reg_write = stk17ta8_nvram_write,
 	};

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

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

 	/* turn RTC on if it was not on */
 	cal = readb(ioaddr + RTC_CALIBRATION);
 	if (cal & RTC_STOP) {
 		cal &= RTC_CAL_MASK;
 		flags = readb(ioaddr + RTC_FLAGS);
 		writeb(flags | RTC_WRITE, ioaddr + RTC_FLAGS);
 		writeb(cal, ioaddr + RTC_CALIBRATION);
 		writeb(flags & ~RTC_WRITE, ioaddr + RTC_FLAGS);
 	}
 	if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_PF)
 		dev_warn(&pdev->dev, "voltage-low detected.\n");

 	spin_lock_init(&pdata->lock);
 	pdata->last_jiffies = jiffies;
 	platform_set_drvdata(pdev, pdata);
 	if (pdata->irq > 0) {
 		writeb(0, ioaddr + RTC_INTERRUPTS);
 		if (devm_request_irq(&pdev->dev, pdata->irq,
 				stk17ta8_rtc_interrupt,
 				IRQF_SHARED,
 				pdev->name, pdev) < 0) {
 			dev_warn(&pdev->dev, "interrupt not available.\n");
 			pdata->irq = 0;
 		}
 	}

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

 	pdata->rtc->ops = &stk17ta8_rtc_ops;
 	pdata->rtc->nvram_old_abi = true;

 	nvmem_cfg.priv = pdata;
 	ret = rtc_nvmem_register(pdata->rtc, &nvmem_cfg);
 	if (ret)
 		return ret;

 	return rtc_register_device(pdata->rtc);
 }

 /* work with hotplug and coldplug */
 MODULE_ALIAS("platform:stk17ta8");

 static struct platform_driver stk17ta8_rtc_driver = {
 	.probe		= stk17ta8_rtc_probe,
 	.driver		= {
 		.name	= "stk17ta8",
 	},
 };

 module_platform_driver(stk17ta8_rtc_driver);

 MODULE_AUTHOR("Thomas Hommel <thomas.hommel@ge.com>");
 MODULE_DESCRIPTION("Simtek STK17TA8 RTC driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* A RTC driver for the Simtek STK17TA8
	*
	* By Thomas Hommel <thomas.hommel@ge.com>
	*
	* Based on the DS1553 driver from
	* Atsushi Nemoto <anemo@mba.ocn.ne.jp>
	*/

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

	#define RTC_REG_SIZE 0x20000
	#define RTC_OFFSET 0x1fff0

	#define RTC_FLAGS (RTC_OFFSET + 0)
	#define RTC_CENTURY (RTC_OFFSET + 1)
	#define RTC_SECONDS_ALARM (RTC_OFFSET + 2)
	#define RTC_MINUTES_ALARM (RTC_OFFSET + 3)
	#define RTC_HOURS_ALARM (RTC_OFFSET + 4)
	#define RTC_DATE_ALARM (RTC_OFFSET + 5)
	#define RTC_INTERRUPTS (RTC_OFFSET + 6)
	#define RTC_WATCHDOG (RTC_OFFSET + 7)
	#define RTC_CALIBRATION (RTC_OFFSET + 8)
	#define RTC_SECONDS (RTC_OFFSET + 9)
	#define RTC_MINUTES (RTC_OFFSET + 10)
	#define RTC_HOURS (RTC_OFFSET + 11)
	#define RTC_DAY (RTC_OFFSET + 12)
	#define RTC_DATE (RTC_OFFSET + 13)
	#define RTC_MONTH (RTC_OFFSET + 14)
	#define RTC_YEAR (RTC_OFFSET + 15)

	#define RTC_SECONDS_MASK 0x7f
	#define RTC_DAY_MASK 0x07
	#define RTC_CAL_MASK 0x3f

	/* Bits in the Calibration register */
	#define RTC_STOP 0x80

	/* Bits in the Flags register */
	#define RTC_FLAGS_AF 0x40
	#define RTC_FLAGS_PF 0x20
	#define RTC_WRITE 0x02
	#define RTC_READ 0x01

	/* Bits in the Interrupts register */
	#define RTC_INTS_AIE 0x40

	struct rtc_plat_data {
	struct rtc_device *rtc;
	void __iomem *ioaddr;
	unsigned long last_jiffies;
	int irq;
	unsigned int irqen;
	int alrm_sec;
	int alrm_min;
	int alrm_hour;
	int alrm_mday;
	spinlock_t lock;
	};

	static int stk17ta8_rtc_set_time(struct device dev, struct rtc_time tm)
	{
	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
	void __iomem *ioaddr = pdata->ioaddr;
	u8 flags;

	flags = readb(pdata->ioaddr + RTC_FLAGS);
	writeb(flags \| RTC_WRITE, pdata->ioaddr + RTC_FLAGS);

	writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
	writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
	writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
	writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
	writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
	writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
	writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);
	writeb(bin2bcd((tm->tm_year + 1900) / 100), ioaddr + RTC_CENTURY);

	writeb(flags & ~RTC_WRITE, pdata->ioaddr + RTC_FLAGS);
	return 0;
	}

	static int stk17ta8_rtc_read_time(struct device dev, struct rtc_time tm)
	{
	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
	void __iomem *ioaddr = pdata->ioaddr;
	unsigned int year, month, day, hour, minute, second, week;
	unsigned int century;
	u8 flags;

	/* give enough time to update RTC in case of continuous read */
	if (pdata->last_jiffies == jiffies)
	msleep(1);
	pdata->last_jiffies = jiffies;

	flags = readb(pdata->ioaddr + RTC_FLAGS);
	writeb(flags \| RTC_READ, ioaddr + RTC_FLAGS);
	second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
	minute = readb(ioaddr + RTC_MINUTES);
	hour = readb(ioaddr + RTC_HOURS);
	day = readb(ioaddr + RTC_DATE);
	week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
	month = readb(ioaddr + RTC_MONTH);
	year = readb(ioaddr + RTC_YEAR);
	century = readb(ioaddr + RTC_CENTURY);
	writeb(flags & ~RTC_READ, ioaddr + RTC_FLAGS);
	tm->tm_sec = bcd2bin(second);
	tm->tm_min = bcd2bin(minute);
	tm->tm_hour = bcd2bin(hour);
	tm->tm_mday = bcd2bin(day);
	tm->tm_wday = bcd2bin(week);
	tm->tm_mon = bcd2bin(month) - 1;
	/* year is 1900 + tm->tm_year */
	tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;

	return 0;
	}

	static void stk17ta8_rtc_update_alarm(struct rtc_plat_data *pdata)
	{
	void __iomem *ioaddr = pdata->ioaddr;
	unsigned long irqflags;
	u8 flags;

	spin_lock_irqsave(&pdata->lock, irqflags);

	flags = readb(ioaddr + RTC_FLAGS);
	writeb(flags \| RTC_WRITE, ioaddr + RTC_FLAGS);

	writeb(pdata->alrm_mday < 0 \|\| (pdata->irqen & RTC_UF) ?
	0x80 : bin2bcd(pdata->alrm_mday),
	ioaddr + RTC_DATE_ALARM);
	writeb(pdata->alrm_hour < 0 \|\| (pdata->irqen & RTC_UF) ?
	0x80 : bin2bcd(pdata->alrm_hour),
	ioaddr + RTC_HOURS_ALARM);
	writeb(pdata->alrm_min < 0 \|\| (pdata->irqen & RTC_UF) ?
	0x80 : bin2bcd(pdata->alrm_min),
	ioaddr + RTC_MINUTES_ALARM);
	writeb(pdata->alrm_sec < 0 \|\| (pdata->irqen & RTC_UF) ?
	0x80 : bin2bcd(pdata->alrm_sec),
	ioaddr + RTC_SECONDS_ALARM);
	writeb(pdata->irqen ? RTC_INTS_AIE : 0, ioaddr + RTC_INTERRUPTS);
	readb(ioaddr + RTC_FLAGS); /* clear interrupts */
	writeb(flags & ~RTC_WRITE, ioaddr + RTC_FLAGS);
	spin_unlock_irqrestore(&pdata->lock, irqflags);
	}

	static int stk17ta8_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;
	stk17ta8_rtc_update_alarm(pdata);
	return 0;
	}

	static int stk17ta8_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 stk17ta8_rtc_interrupt(int irq, void *dev_id)
	{
	struct platform_device *pdev = dev_id;
	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
	void __iomem *ioaddr = pdata->ioaddr;
	unsigned long events = 0;

	spin_lock(&pdata->lock);
	/* read and clear interrupt */
	if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_AF) {
	events = RTC_IRQF;
	if (readb(ioaddr + RTC_SECONDS_ALARM) & 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 stk17ta8_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;
	stk17ta8_rtc_update_alarm(pdata);
	return 0;
	}

	static const struct rtc_class_ops stk17ta8_rtc_ops = {
	.read_time = stk17ta8_rtc_read_time,
	.set_time = stk17ta8_rtc_set_time,
	.read_alarm = stk17ta8_rtc_read_alarm,
	.set_alarm = stk17ta8_rtc_set_alarm,
	.alarm_irq_enable = stk17ta8_rtc_alarm_irq_enable,
	};

	static int stk17ta8_nvram_read(void priv, unsigned int pos, void val,
	size_t bytes)
	{
	struct rtc_plat_data *pdata = priv;
	void __iomem *ioaddr = pdata->ioaddr;
	u8 *buf = val;

	for (; bytes; bytes--)
	*buf++ = readb(ioaddr + pos++);
	return 0;
	}

	static int stk17ta8_nvram_write(void priv, unsigned int pos, void val,
	size_t bytes)
	{
	struct rtc_plat_data *pdata = priv;
	void __iomem *ioaddr = pdata->ioaddr;
	u8 *buf = val;

	for (; bytes; bytes--)
	writeb(*buf++, ioaddr + pos++);
	return 0;
	}

	static int stk17ta8_rtc_probe(struct platform_device *pdev)
	{
	struct resource *res;
	unsigned int cal;
	unsigned int flags;
	struct rtc_plat_data *pdata;
	void __iomem *ioaddr;
	int ret = 0;
	struct nvmem_config nvmem_cfg = {
	.name = "stk17ta8_nvram",
	.word_size = 1,
	.stride = 1,
	.size = RTC_OFFSET,
	.reg_read = stk17ta8_nvram_read,
	.reg_write = stk17ta8_nvram_write,
	};

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

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

	/* turn RTC on if it was not on */
	cal = readb(ioaddr + RTC_CALIBRATION);
	if (cal & RTC_STOP) {
	cal &= RTC_CAL_MASK;
	flags = readb(ioaddr + RTC_FLAGS);
	writeb(flags \| RTC_WRITE, ioaddr + RTC_FLAGS);
	writeb(cal, ioaddr + RTC_CALIBRATION);
	writeb(flags & ~RTC_WRITE, ioaddr + RTC_FLAGS);
	}
	if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_PF)
	dev_warn(&pdev->dev, "voltage-low detected.\n");

	spin_lock_init(&pdata->lock);
	pdata->last_jiffies = jiffies;
	platform_set_drvdata(pdev, pdata);
	if (pdata->irq > 0) {
	writeb(0, ioaddr + RTC_INTERRUPTS);
	if (devm_request_irq(&pdev->dev, pdata->irq,
	stk17ta8_rtc_interrupt,
	IRQF_SHARED,
	pdev->name, pdev) < 0) {
	dev_warn(&pdev->dev, "interrupt not available.\n");
	pdata->irq = 0;
	}
	}

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

	pdata->rtc->ops = &stk17ta8_rtc_ops;
	pdata->rtc->nvram_old_abi = true;

	nvmem_cfg.priv = pdata;
	ret = rtc_nvmem_register(pdata->rtc, &nvmem_cfg);
	if (ret)
	return ret;

	return rtc_register_device(pdata->rtc);
	}

	/* work with hotplug and coldplug */
	MODULE_ALIAS("platform:stk17ta8");

	static struct platform_driver stk17ta8_rtc_driver = {
	.probe = stk17ta8_rtc_probe,
	.driver = {
	.name = "stk17ta8",
	},
	};

	module_platform_driver(stk17ta8_rtc_driver);

	MODULE_AUTHOR("Thomas Hommel <thomas.hommel@ge.com>");
	MODULE_DESCRIPTION("Simtek STK17TA8 RTC driver");
	MODULE_LICENSE("GPL");