drivers/rtc/rtc-sirfsoc.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * SiRFSoC Real Time Clock interface for Linux
  *
  * Copyright (c) 2013 Cambridge Silicon Radio Limited, a CSR plc group company.
  */

 #include <linux/module.h>
 #include <linux/err.h>
 #include <linux/rtc.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/regmap.h>
 #include <linux/rtc/sirfsoc_rtciobrg.h>


 #define RTC_CN			0x00
 #define RTC_ALARM0		0x04
 #define RTC_ALARM1		0x18
 #define RTC_STATUS		0x08
 #define RTC_SW_VALUE            0x40
 #define SIRFSOC_RTC_AL1E	(1<<6)
 #define SIRFSOC_RTC_AL1		(1<<4)
 #define SIRFSOC_RTC_HZE		(1<<3)
 #define SIRFSOC_RTC_AL0E	(1<<2)
 #define SIRFSOC_RTC_HZ		(1<<1)
 #define SIRFSOC_RTC_AL0		(1<<0)
 #define RTC_DIV			0x0c
 #define RTC_DEEP_CTRL		0x14
 #define RTC_CLOCK_SWITCH	0x1c
 #define SIRFSOC_RTC_CLK		0x03	/* others are reserved */

 /* Refer to RTC DIV switch */
 #define RTC_HZ			16

 /* This macro is also defined in arch/arm/plat-sirfsoc/cpu.c */
 #define RTC_SHIFT		4

 #define INTR_SYSRTC_CN		0x48

 struct sirfsoc_rtc_drv {
 	struct rtc_device	*rtc;
 	u32			rtc_base;
 	u32			irq;
 	unsigned		irq_wake;
 	/* Overflow for every 8 years extra time */
 	u32			overflow_rtc;
 	spinlock_t		lock;
 	struct regmap *regmap;
 #ifdef CONFIG_PM
 	u32		saved_counter;
 	u32		saved_overflow_rtc;
 #endif
 };

 static u32 sirfsoc_rtc_readl(struct sirfsoc_rtc_drv *rtcdrv, u32 offset)
 {
 	u32 val;

 	regmap_read(rtcdrv->regmap, rtcdrv->rtc_base + offset, &val);
 	return val;
 }

 static void sirfsoc_rtc_writel(struct sirfsoc_rtc_drv *rtcdrv,
 			       u32 offset, u32 val)
 {
 	regmap_write(rtcdrv->regmap, rtcdrv->rtc_base + offset, val);
 }

 static int sirfsoc_rtc_read_alarm(struct device *dev,
 		struct rtc_wkalrm *alrm)
 {
 	unsigned long rtc_alarm, rtc_count;
 	struct sirfsoc_rtc_drv *rtcdrv;

 	rtcdrv = dev_get_drvdata(dev);

 	spin_lock_irq(&rtcdrv->lock);

 	rtc_count = sirfsoc_rtc_readl(rtcdrv, RTC_CN);

 	rtc_alarm = sirfsoc_rtc_readl(rtcdrv, RTC_ALARM0);
 	memset(alrm, 0, sizeof(struct rtc_wkalrm));

 	/*
 	 * assume alarm interval not beyond one round counter overflow_rtc:
 	 * 0->0xffffffff
 	 */
 	/* if alarm is in next overflow cycle */
 	if (rtc_count > rtc_alarm)
 		rtc_time_to_tm((rtcdrv->overflow_rtc + 1)
 				<< (BITS_PER_LONG - RTC_SHIFT)
 				| rtc_alarm >> RTC_SHIFT, &(alrm->time));
 	else
 		rtc_time_to_tm(rtcdrv->overflow_rtc
 				<< (BITS_PER_LONG - RTC_SHIFT)
 				| rtc_alarm >> RTC_SHIFT, &(alrm->time));
 	if (sirfsoc_rtc_readl(rtcdrv, RTC_STATUS) & SIRFSOC_RTC_AL0E)
 		alrm->enabled = 1;

 	spin_unlock_irq(&rtcdrv->lock);

 	return 0;
 }

 static int sirfsoc_rtc_set_alarm(struct device *dev,
 		struct rtc_wkalrm *alrm)
 {
 	unsigned long rtc_status_reg, rtc_alarm;
 	struct sirfsoc_rtc_drv *rtcdrv;
 	rtcdrv = dev_get_drvdata(dev);

 	if (alrm->enabled) {
 		rtc_tm_to_time(&(alrm->time), &rtc_alarm);

 		spin_lock_irq(&rtcdrv->lock);

 		rtc_status_reg = sirfsoc_rtc_readl(rtcdrv, RTC_STATUS);
 		if (rtc_status_reg & SIRFSOC_RTC_AL0E) {
 			/*
 			 * An ongoing alarm in progress - ingore it and not
 			 * to return EBUSY
 			 */
 			dev_info(dev, "An old alarm was set, will be replaced by a new one\n");
 		}

 		sirfsoc_rtc_writel(rtcdrv, RTC_ALARM0, rtc_alarm << RTC_SHIFT);
 		rtc_status_reg &= ~0x07; /* mask out the lower status bits */
 		/*
 		 * This bit RTC_AL sets it as a wake-up source for Sleep Mode
 		 * Writing 1 into this bit will clear it
 		 */
 		rtc_status_reg |= SIRFSOC_RTC_AL0;
 		/* enable the RTC alarm interrupt */
 		rtc_status_reg |= SIRFSOC_RTC_AL0E;
 		sirfsoc_rtc_writel(rtcdrv, RTC_STATUS, rtc_status_reg);

 		spin_unlock_irq(&rtcdrv->lock);
 	} else {
 		/*
 		 * if this function was called with enabled=0
 		 * then it could mean that the application is
 		 * trying to cancel an ongoing alarm
 		 */
 		spin_lock_irq(&rtcdrv->lock);

 		rtc_status_reg = sirfsoc_rtc_readl(rtcdrv, RTC_STATUS);
 		if (rtc_status_reg & SIRFSOC_RTC_AL0E) {
 			/* clear the RTC status register's alarm bit */
 			rtc_status_reg &= ~0x07;
 			/* write 1 into SIRFSOC_RTC_AL0 to force a clear */
 			rtc_status_reg |= (SIRFSOC_RTC_AL0);
 			/* Clear the Alarm enable bit */
 			rtc_status_reg &= ~(SIRFSOC_RTC_AL0E);

 			sirfsoc_rtc_writel(rtcdrv, RTC_STATUS,
 					   rtc_status_reg);
 		}

 		spin_unlock_irq(&rtcdrv->lock);
 	}

 	return 0;
 }

 static int sirfsoc_rtc_read_time(struct device *dev,
 		struct rtc_time *tm)
 {
 	unsigned long tmp_rtc = 0;
 	struct sirfsoc_rtc_drv *rtcdrv;
 	rtcdrv = dev_get_drvdata(dev);
 	/*
 	 * This patch is taken from WinCE - Need to validate this for
 	 * correctness. To work around sirfsoc RTC counter double sync logic
 	 * fail, read several times to make sure get stable value.
 	 */
 	do {
 		tmp_rtc = sirfsoc_rtc_readl(rtcdrv, RTC_CN);
 		cpu_relax();
 	} while (tmp_rtc != sirfsoc_rtc_readl(rtcdrv, RTC_CN));

 	rtc_time_to_tm(rtcdrv->overflow_rtc << (BITS_PER_LONG - RTC_SHIFT) |
 					tmp_rtc >> RTC_SHIFT, tm);
 	return 0;
 }

 static int sirfsoc_rtc_set_time(struct device *dev,
 		struct rtc_time *tm)
 {
 	unsigned long rtc_time;
 	struct sirfsoc_rtc_drv *rtcdrv;
 	rtcdrv = dev_get_drvdata(dev);

 	rtc_tm_to_time(tm, &rtc_time);

 	rtcdrv->overflow_rtc = rtc_time >> (BITS_PER_LONG - RTC_SHIFT);

 	sirfsoc_rtc_writel(rtcdrv, RTC_SW_VALUE, rtcdrv->overflow_rtc);
 	sirfsoc_rtc_writel(rtcdrv, RTC_CN, rtc_time << RTC_SHIFT);

 	return 0;
 }

 static int sirfsoc_rtc_alarm_irq_enable(struct device *dev,
 		unsigned int enabled)
 {
 	unsigned long rtc_status_reg = 0x0;
 	struct sirfsoc_rtc_drv *rtcdrv;

 	rtcdrv = dev_get_drvdata(dev);

 	spin_lock_irq(&rtcdrv->lock);

 	rtc_status_reg = sirfsoc_rtc_readl(rtcdrv, RTC_STATUS);
 	if (enabled)
 		rtc_status_reg |= SIRFSOC_RTC_AL0E;
 	else
 		rtc_status_reg &= ~SIRFSOC_RTC_AL0E;

 	sirfsoc_rtc_writel(rtcdrv, RTC_STATUS, rtc_status_reg);

 	spin_unlock_irq(&rtcdrv->lock);

 	return 0;

 }

 static const struct rtc_class_ops sirfsoc_rtc_ops = {
 	.read_time = sirfsoc_rtc_read_time,
 	.set_time = sirfsoc_rtc_set_time,
 	.read_alarm = sirfsoc_rtc_read_alarm,
 	.set_alarm = sirfsoc_rtc_set_alarm,
 	.alarm_irq_enable = sirfsoc_rtc_alarm_irq_enable
 };

 static irqreturn_t sirfsoc_rtc_irq_handler(int irq, void *pdata)
 {
 	struct sirfsoc_rtc_drv *rtcdrv = pdata;
 	unsigned long rtc_status_reg = 0x0;
 	unsigned long events = 0x0;

 	spin_lock(&rtcdrv->lock);

 	rtc_status_reg = sirfsoc_rtc_readl(rtcdrv, RTC_STATUS);
 	/* this bit will be set ONLY if an alarm was active
 	 * and it expired NOW
 	 * So this is being used as an ASSERT
 	 */
 	if (rtc_status_reg & SIRFSOC_RTC_AL0) {
 		/*
 		 * clear the RTC status register's alarm bit
 		 * mask out the lower status bits
 		 */
 		rtc_status_reg &= ~0x07;
 		/* write 1 into SIRFSOC_RTC_AL0 to ACK the alarm interrupt */
 		rtc_status_reg |= (SIRFSOC_RTC_AL0);
 		/* Clear the Alarm enable bit */
 		rtc_status_reg &= ~(SIRFSOC_RTC_AL0E);
 	}

 	sirfsoc_rtc_writel(rtcdrv, RTC_STATUS, rtc_status_reg);

 	spin_unlock(&rtcdrv->lock);

 	/* this should wake up any apps polling/waiting on the read
 	 * after setting the alarm
 	 */
 	events |= RTC_IRQF | RTC_AF;
 	rtc_update_irq(rtcdrv->rtc, 1, events);

 	return IRQ_HANDLED;
 }

 static const struct of_device_id sirfsoc_rtc_of_match[] = {
 	{ .compatible = "sirf,prima2-sysrtc"},
 	{},
 };

 static const struct regmap_config sysrtc_regmap_config = {
 	.reg_bits = 32,
 	.val_bits = 32,
 	.fast_io = true,
 };

 MODULE_DEVICE_TABLE(of, sirfsoc_rtc_of_match);

 static int sirfsoc_rtc_probe(struct platform_device *pdev)
 {
 	int err;
 	unsigned long rtc_div;
 	struct sirfsoc_rtc_drv *rtcdrv;
 	struct device_node *np = pdev->dev.of_node;

 	rtcdrv = devm_kzalloc(&pdev->dev,
 		sizeof(struct sirfsoc_rtc_drv), GFP_KERNEL);
 	if (rtcdrv == NULL)
 		return -ENOMEM;

 	spin_lock_init(&rtcdrv->lock);

 	err = of_property_read_u32(np, "reg", &rtcdrv->rtc_base);
 	if (err) {
 		dev_err(&pdev->dev, "unable to find base address of rtc node in dtb\n");
 		return err;
 	}

 	platform_set_drvdata(pdev, rtcdrv);

 	/* Register rtc alarm as a wakeup source */
 	device_init_wakeup(&pdev->dev, 1);

 	rtcdrv->regmap = devm_regmap_init_iobg(&pdev->dev,
 			&sysrtc_regmap_config);
 	if (IS_ERR(rtcdrv->regmap)) {
 		err = PTR_ERR(rtcdrv->regmap);
 		dev_err(&pdev->dev, "Failed to allocate register map: %d\n",
 			err);
 		return err;
 	}

 	/*
 	 * Set SYS_RTC counter in RTC_HZ HZ Units
 	 * We are using 32K RTC crystal (32768 / RTC_HZ / 2) -1
 	 * If 16HZ, therefore RTC_DIV = 1023;
 	 */
 	rtc_div = ((32768 / RTC_HZ) / 2) - 1;
 	sirfsoc_rtc_writel(rtcdrv, RTC_DIV, rtc_div);

 	/* 0x3 -> RTC_CLK */
 	sirfsoc_rtc_writel(rtcdrv, RTC_CLOCK_SWITCH, SIRFSOC_RTC_CLK);

 	/* reset SYS RTC ALARM0 */
 	sirfsoc_rtc_writel(rtcdrv, RTC_ALARM0, 0x0);

 	/* reset SYS RTC ALARM1 */
 	sirfsoc_rtc_writel(rtcdrv, RTC_ALARM1, 0x0);

 	/* Restore RTC Overflow From Register After Command Reboot */
 	rtcdrv->overflow_rtc =
 		sirfsoc_rtc_readl(rtcdrv, RTC_SW_VALUE);

 	rtcdrv->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
 			&sirfsoc_rtc_ops, THIS_MODULE);
 	if (IS_ERR(rtcdrv->rtc)) {
 		err = PTR_ERR(rtcdrv->rtc);
 		dev_err(&pdev->dev, "can't register RTC device\n");
 		return err;
 	}

 	rtcdrv->irq = platform_get_irq(pdev, 0);
 	err = devm_request_irq(
 			&pdev->dev,
 			rtcdrv->irq,
 			sirfsoc_rtc_irq_handler,
 			IRQF_SHARED,
 			pdev->name,
 			rtcdrv);
 	if (err) {
 		dev_err(&pdev->dev, "Unable to register for the SiRF SOC RTC IRQ\n");
 		return err;
 	}

 	return 0;
 }

 #ifdef CONFIG_PM_SLEEP
 static int sirfsoc_rtc_suspend(struct device *dev)
 {
 	struct sirfsoc_rtc_drv *rtcdrv = dev_get_drvdata(dev);
 	rtcdrv->overflow_rtc =
 		sirfsoc_rtc_readl(rtcdrv, RTC_SW_VALUE);

 	rtcdrv->saved_counter =
 		sirfsoc_rtc_readl(rtcdrv, RTC_CN);
 	rtcdrv->saved_overflow_rtc = rtcdrv->overflow_rtc;
 	if (device_may_wakeup(dev) && !enable_irq_wake(rtcdrv->irq))
 		rtcdrv->irq_wake = 1;

 	return 0;
 }

 static int sirfsoc_rtc_resume(struct device *dev)
 {
 	u32 tmp;
 	struct sirfsoc_rtc_drv *rtcdrv = dev_get_drvdata(dev);

 	/*
 	 * if resume from snapshot and the rtc power is lost,
 	 * restroe the rtc settings
 	 */
 	if (SIRFSOC_RTC_CLK != sirfsoc_rtc_readl(rtcdrv, RTC_CLOCK_SWITCH)) {
 		u32 rtc_div;
 		/* 0x3 -> RTC_CLK */
 		sirfsoc_rtc_writel(rtcdrv, RTC_CLOCK_SWITCH, SIRFSOC_RTC_CLK);
 		/*
 		 * Set SYS_RTC counter in RTC_HZ HZ Units
 		 * We are using 32K RTC crystal (32768 / RTC_HZ / 2) -1
 		 * If 16HZ, therefore RTC_DIV = 1023;
 		 */
 		rtc_div = ((32768 / RTC_HZ) / 2) - 1;

 		sirfsoc_rtc_writel(rtcdrv, RTC_DIV, rtc_div);

 		/* reset SYS RTC ALARM0 */
 		sirfsoc_rtc_writel(rtcdrv, RTC_ALARM0, 0x0);

 		/* reset SYS RTC ALARM1 */
 		sirfsoc_rtc_writel(rtcdrv, RTC_ALARM1, 0x0);
 	}
 	rtcdrv->overflow_rtc = rtcdrv->saved_overflow_rtc;

 	/*
 	 * if current counter is small than previous,
 	 * it means overflow in sleep
 	 */
 	tmp = sirfsoc_rtc_readl(rtcdrv, RTC_CN);
 	if (tmp <= rtcdrv->saved_counter)
 		rtcdrv->overflow_rtc++;
 	/*
 	 *PWRC Value Be Changed When Suspend, Restore Overflow
 	 * In Memory To Register
 	 */
 	sirfsoc_rtc_writel(rtcdrv, RTC_SW_VALUE, rtcdrv->overflow_rtc);

 	if (device_may_wakeup(dev) && rtcdrv->irq_wake) {
 		disable_irq_wake(rtcdrv->irq);
 		rtcdrv->irq_wake = 0;
 	}

 	return 0;
 }
 #endif

 static SIMPLE_DEV_PM_OPS(sirfsoc_rtc_pm_ops,
 		sirfsoc_rtc_suspend, sirfsoc_rtc_resume);

 static struct platform_driver sirfsoc_rtc_driver = {
 	.driver = {
 		.name = "sirfsoc-rtc",
 		.pm = &sirfsoc_rtc_pm_ops,
 		.of_match_table = sirfsoc_rtc_of_match,
 	},
 	.probe = sirfsoc_rtc_probe,
 };
 module_platform_driver(sirfsoc_rtc_driver);

 MODULE_DESCRIPTION("SiRF SoC rtc driver");
 MODULE_AUTHOR("Xianglong Du <Xianglong.Du@csr.com>");
 MODULE_LICENSE("GPL v2");
 MODULE_ALIAS("platform:sirfsoc-rtc");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* SiRFSoC Real Time Clock interface for Linux
	*
	* Copyright (c) 2013 Cambridge Silicon Radio Limited, a CSR plc group company.
	*/

	#include <linux/module.h>
	#include <linux/err.h>
	#include <linux/rtc.h>
	#include <linux/platform_device.h>
	#include <linux/slab.h>
	#include <linux/io.h>
	#include <linux/of.h>
	#include <linux/regmap.h>
	#include <linux/rtc/sirfsoc_rtciobrg.h>


	#define RTC_CN 0x00
	#define RTC_ALARM0 0x04
	#define RTC_ALARM1 0x18
	#define RTC_STATUS 0x08
	#define RTC_SW_VALUE 0x40
	#define SIRFSOC_RTC_AL1E (1<<6)
	#define SIRFSOC_RTC_AL1 (1<<4)
	#define SIRFSOC_RTC_HZE (1<<3)
	#define SIRFSOC_RTC_AL0E (1<<2)
	#define SIRFSOC_RTC_HZ (1<<1)
	#define SIRFSOC_RTC_AL0 (1<<0)
	#define RTC_DIV 0x0c
	#define RTC_DEEP_CTRL 0x14
	#define RTC_CLOCK_SWITCH 0x1c
	#define SIRFSOC_RTC_CLK 0x03 /* others are reserved */

	/* Refer to RTC DIV switch */
	#define RTC_HZ 16

	/* This macro is also defined in arch/arm/plat-sirfsoc/cpu.c */
	#define RTC_SHIFT 4

	#define INTR_SYSRTC_CN 0x48

	struct sirfsoc_rtc_drv {
	struct rtc_device *rtc;
	u32 rtc_base;
	u32 irq;
	unsigned irq_wake;
	/* Overflow for every 8 years extra time */
	u32 overflow_rtc;
	spinlock_t lock;
	struct regmap *regmap;
	#ifdef CONFIG_PM
	u32 saved_counter;
	u32 saved_overflow_rtc;
	#endif
	};

	static u32 sirfsoc_rtc_readl(struct sirfsoc_rtc_drv *rtcdrv, u32 offset)
	{
	u32 val;

	regmap_read(rtcdrv->regmap, rtcdrv->rtc_base + offset, &val);
	return val;
	}

	static void sirfsoc_rtc_writel(struct sirfsoc_rtc_drv *rtcdrv,
	u32 offset, u32 val)
	{
	regmap_write(rtcdrv->regmap, rtcdrv->rtc_base + offset, val);
	}

	static int sirfsoc_rtc_read_alarm(struct device *dev,
	struct rtc_wkalrm *alrm)
	{
	unsigned long rtc_alarm, rtc_count;
	struct sirfsoc_rtc_drv *rtcdrv;

	rtcdrv = dev_get_drvdata(dev);

	spin_lock_irq(&rtcdrv->lock);

	rtc_count = sirfsoc_rtc_readl(rtcdrv, RTC_CN);

	rtc_alarm = sirfsoc_rtc_readl(rtcdrv, RTC_ALARM0);
	memset(alrm, 0, sizeof(struct rtc_wkalrm));

	/*
	* assume alarm interval not beyond one round counter overflow_rtc:
	* 0->0xffffffff
	*/
	/* if alarm is in next overflow cycle */
	if (rtc_count > rtc_alarm)
	rtc_time_to_tm((rtcdrv->overflow_rtc + 1)
	<< (BITS_PER_LONG - RTC_SHIFT)
	\| rtc_alarm >> RTC_SHIFT, &(alrm->time));
	else
	rtc_time_to_tm(rtcdrv->overflow_rtc
	<< (BITS_PER_LONG - RTC_SHIFT)
	\| rtc_alarm >> RTC_SHIFT, &(alrm->time));
	if (sirfsoc_rtc_readl(rtcdrv, RTC_STATUS) & SIRFSOC_RTC_AL0E)
	alrm->enabled = 1;

	spin_unlock_irq(&rtcdrv->lock);

	return 0;
	}

	static int sirfsoc_rtc_set_alarm(struct device *dev,
	struct rtc_wkalrm *alrm)
	{
	unsigned long rtc_status_reg, rtc_alarm;
	struct sirfsoc_rtc_drv *rtcdrv;
	rtcdrv = dev_get_drvdata(dev);

	if (alrm->enabled) {
	rtc_tm_to_time(&(alrm->time), &rtc_alarm);

	spin_lock_irq(&rtcdrv->lock);

	rtc_status_reg = sirfsoc_rtc_readl(rtcdrv, RTC_STATUS);
	if (rtc_status_reg & SIRFSOC_RTC_AL0E) {
	/*
	* An ongoing alarm in progress - ingore it and not
	* to return EBUSY
	*/
	dev_info(dev, "An old alarm was set, will be replaced by a new one\n");
	}

	sirfsoc_rtc_writel(rtcdrv, RTC_ALARM0, rtc_alarm << RTC_SHIFT);
	rtc_status_reg &= ~0x07; /* mask out the lower status bits */
	/*
	* This bit RTC_AL sets it as a wake-up source for Sleep Mode
	* Writing 1 into this bit will clear it
	*/
	rtc_status_reg \|= SIRFSOC_RTC_AL0;
	/* enable the RTC alarm interrupt */
	rtc_status_reg \|= SIRFSOC_RTC_AL0E;
	sirfsoc_rtc_writel(rtcdrv, RTC_STATUS, rtc_status_reg);

	spin_unlock_irq(&rtcdrv->lock);
	} else {
	/*
	* if this function was called with enabled=0
	* then it could mean that the application is
	* trying to cancel an ongoing alarm
	*/
	spin_lock_irq(&rtcdrv->lock);

	rtc_status_reg = sirfsoc_rtc_readl(rtcdrv, RTC_STATUS);
	if (rtc_status_reg & SIRFSOC_RTC_AL0E) {
	/* clear the RTC status register's alarm bit */
	rtc_status_reg &= ~0x07;
	/* write 1 into SIRFSOC_RTC_AL0 to force a clear */
	rtc_status_reg \|= (SIRFSOC_RTC_AL0);
	/* Clear the Alarm enable bit */
	rtc_status_reg &= ~(SIRFSOC_RTC_AL0E);

	sirfsoc_rtc_writel(rtcdrv, RTC_STATUS,
	rtc_status_reg);
	}

	spin_unlock_irq(&rtcdrv->lock);
	}

	return 0;
	}

	static int sirfsoc_rtc_read_time(struct device *dev,
	struct rtc_time *tm)
	{
	unsigned long tmp_rtc = 0;
	struct sirfsoc_rtc_drv *rtcdrv;
	rtcdrv = dev_get_drvdata(dev);
	/*
	* This patch is taken from WinCE - Need to validate this for
	* correctness. To work around sirfsoc RTC counter double sync logic
	* fail, read several times to make sure get stable value.
	*/
	do {
	tmp_rtc = sirfsoc_rtc_readl(rtcdrv, RTC_CN);
	cpu_relax();
	} while (tmp_rtc != sirfsoc_rtc_readl(rtcdrv, RTC_CN));

	rtc_time_to_tm(rtcdrv->overflow_rtc << (BITS_PER_LONG - RTC_SHIFT) \|
	tmp_rtc >> RTC_SHIFT, tm);
	return 0;
	}

	static int sirfsoc_rtc_set_time(struct device *dev,
	struct rtc_time *tm)
	{
	unsigned long rtc_time;
	struct sirfsoc_rtc_drv *rtcdrv;
	rtcdrv = dev_get_drvdata(dev);

	rtc_tm_to_time(tm, &rtc_time);

	rtcdrv->overflow_rtc = rtc_time >> (BITS_PER_LONG - RTC_SHIFT);

	sirfsoc_rtc_writel(rtcdrv, RTC_SW_VALUE, rtcdrv->overflow_rtc);
	sirfsoc_rtc_writel(rtcdrv, RTC_CN, rtc_time << RTC_SHIFT);

	return 0;
	}

	static int sirfsoc_rtc_alarm_irq_enable(struct device *dev,
	unsigned int enabled)
	{
	unsigned long rtc_status_reg = 0x0;
	struct sirfsoc_rtc_drv *rtcdrv;

	rtcdrv = dev_get_drvdata(dev);

	spin_lock_irq(&rtcdrv->lock);

	rtc_status_reg = sirfsoc_rtc_readl(rtcdrv, RTC_STATUS);
	if (enabled)
	rtc_status_reg \|= SIRFSOC_RTC_AL0E;
	else
	rtc_status_reg &= ~SIRFSOC_RTC_AL0E;

	sirfsoc_rtc_writel(rtcdrv, RTC_STATUS, rtc_status_reg);

	spin_unlock_irq(&rtcdrv->lock);

	return 0;

	}

	static const struct rtc_class_ops sirfsoc_rtc_ops = {
	.read_time = sirfsoc_rtc_read_time,
	.set_time = sirfsoc_rtc_set_time,
	.read_alarm = sirfsoc_rtc_read_alarm,
	.set_alarm = sirfsoc_rtc_set_alarm,
	.alarm_irq_enable = sirfsoc_rtc_alarm_irq_enable
	};

	static irqreturn_t sirfsoc_rtc_irq_handler(int irq, void *pdata)
	{
	struct sirfsoc_rtc_drv *rtcdrv = pdata;
	unsigned long rtc_status_reg = 0x0;
	unsigned long events = 0x0;

	spin_lock(&rtcdrv->lock);

	rtc_status_reg = sirfsoc_rtc_readl(rtcdrv, RTC_STATUS);
	/* this bit will be set ONLY if an alarm was active
	* and it expired NOW
	* So this is being used as an ASSERT
	*/
	if (rtc_status_reg & SIRFSOC_RTC_AL0) {
	/*
	* clear the RTC status register's alarm bit
	* mask out the lower status bits
	*/
	rtc_status_reg &= ~0x07;
	/* write 1 into SIRFSOC_RTC_AL0 to ACK the alarm interrupt */
	rtc_status_reg \|= (SIRFSOC_RTC_AL0);
	/* Clear the Alarm enable bit */
	rtc_status_reg &= ~(SIRFSOC_RTC_AL0E);
	}

	sirfsoc_rtc_writel(rtcdrv, RTC_STATUS, rtc_status_reg);

	spin_unlock(&rtcdrv->lock);

	/* this should wake up any apps polling/waiting on the read
	* after setting the alarm
	*/
	events \|= RTC_IRQF \| RTC_AF;
	rtc_update_irq(rtcdrv->rtc, 1, events);

	return IRQ_HANDLED;
	}

	static const struct of_device_id sirfsoc_rtc_of_match[] = {
	{ .compatible = "sirf,prima2-sysrtc"},
	{},
	};

	static const struct regmap_config sysrtc_regmap_config = {
	.reg_bits = 32,
	.val_bits = 32,
	.fast_io = true,
	};

	MODULE_DEVICE_TABLE(of, sirfsoc_rtc_of_match);

	static int sirfsoc_rtc_probe(struct platform_device *pdev)
	{
	int err;
	unsigned long rtc_div;
	struct sirfsoc_rtc_drv *rtcdrv;
	struct device_node *np = pdev->dev.of_node;

	rtcdrv = devm_kzalloc(&pdev->dev,
	sizeof(struct sirfsoc_rtc_drv), GFP_KERNEL);
	if (rtcdrv == NULL)
	return -ENOMEM;

	spin_lock_init(&rtcdrv->lock);

	err = of_property_read_u32(np, "reg", &rtcdrv->rtc_base);
	if (err) {
	dev_err(&pdev->dev, "unable to find base address of rtc node in dtb\n");
	return err;
	}

	platform_set_drvdata(pdev, rtcdrv);

	/* Register rtc alarm as a wakeup source */
	device_init_wakeup(&pdev->dev, 1);

	rtcdrv->regmap = devm_regmap_init_iobg(&pdev->dev,
	&sysrtc_regmap_config);
	if (IS_ERR(rtcdrv->regmap)) {
	err = PTR_ERR(rtcdrv->regmap);
	dev_err(&pdev->dev, "Failed to allocate register map: %d\n",
	err);
	return err;
	}

	/*
	* Set SYS_RTC counter in RTC_HZ HZ Units
	* We are using 32K RTC crystal (32768 / RTC_HZ / 2) -1
	* If 16HZ, therefore RTC_DIV = 1023;
	*/
	rtc_div = ((32768 / RTC_HZ) / 2) - 1;
	sirfsoc_rtc_writel(rtcdrv, RTC_DIV, rtc_div);

	/* 0x3 -> RTC_CLK */
	sirfsoc_rtc_writel(rtcdrv, RTC_CLOCK_SWITCH, SIRFSOC_RTC_CLK);

	/* reset SYS RTC ALARM0 */
	sirfsoc_rtc_writel(rtcdrv, RTC_ALARM0, 0x0);

	/* reset SYS RTC ALARM1 */
	sirfsoc_rtc_writel(rtcdrv, RTC_ALARM1, 0x0);

	/* Restore RTC Overflow From Register After Command Reboot */
	rtcdrv->overflow_rtc =
	sirfsoc_rtc_readl(rtcdrv, RTC_SW_VALUE);

	rtcdrv->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
	&sirfsoc_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtcdrv->rtc)) {
	err = PTR_ERR(rtcdrv->rtc);
	dev_err(&pdev->dev, "can't register RTC device\n");
	return err;
	}

	rtcdrv->irq = platform_get_irq(pdev, 0);
	err = devm_request_irq(
	&pdev->dev,
	rtcdrv->irq,
	sirfsoc_rtc_irq_handler,
	IRQF_SHARED,
	pdev->name,
	rtcdrv);
	if (err) {
	dev_err(&pdev->dev, "Unable to register for the SiRF SOC RTC IRQ\n");
	return err;
	}

	return 0;
	}

	#ifdef CONFIG_PM_SLEEP
	static int sirfsoc_rtc_suspend(struct device *dev)
	{
	struct sirfsoc_rtc_drv *rtcdrv = dev_get_drvdata(dev);
	rtcdrv->overflow_rtc =
	sirfsoc_rtc_readl(rtcdrv, RTC_SW_VALUE);

	rtcdrv->saved_counter =
	sirfsoc_rtc_readl(rtcdrv, RTC_CN);
	rtcdrv->saved_overflow_rtc = rtcdrv->overflow_rtc;
	if (device_may_wakeup(dev) && !enable_irq_wake(rtcdrv->irq))
	rtcdrv->irq_wake = 1;

	return 0;
	}

	static int sirfsoc_rtc_resume(struct device *dev)
	{
	u32 tmp;
	struct sirfsoc_rtc_drv *rtcdrv = dev_get_drvdata(dev);

	/*
	* if resume from snapshot and the rtc power is lost,
	* restroe the rtc settings
	*/
	if (SIRFSOC_RTC_CLK != sirfsoc_rtc_readl(rtcdrv, RTC_CLOCK_SWITCH)) {
	u32 rtc_div;
	/* 0x3 -> RTC_CLK */
	sirfsoc_rtc_writel(rtcdrv, RTC_CLOCK_SWITCH, SIRFSOC_RTC_CLK);
	/*
	* Set SYS_RTC counter in RTC_HZ HZ Units
	* We are using 32K RTC crystal (32768 / RTC_HZ / 2) -1
	* If 16HZ, therefore RTC_DIV = 1023;
	*/
	rtc_div = ((32768 / RTC_HZ) / 2) - 1;

	sirfsoc_rtc_writel(rtcdrv, RTC_DIV, rtc_div);

	/* reset SYS RTC ALARM0 */
	sirfsoc_rtc_writel(rtcdrv, RTC_ALARM0, 0x0);

	/* reset SYS RTC ALARM1 */
	sirfsoc_rtc_writel(rtcdrv, RTC_ALARM1, 0x0);
	}
	rtcdrv->overflow_rtc = rtcdrv->saved_overflow_rtc;

	/*
	* if current counter is small than previous,
	* it means overflow in sleep
	*/
	tmp = sirfsoc_rtc_readl(rtcdrv, RTC_CN);
	if (tmp <= rtcdrv->saved_counter)
	rtcdrv->overflow_rtc++;
	/*
	*PWRC Value Be Changed When Suspend, Restore Overflow
	* In Memory To Register
	*/
	sirfsoc_rtc_writel(rtcdrv, RTC_SW_VALUE, rtcdrv->overflow_rtc);

	if (device_may_wakeup(dev) && rtcdrv->irq_wake) {
	disable_irq_wake(rtcdrv->irq);
	rtcdrv->irq_wake = 0;
	}

	return 0;
	}
	#endif

	static SIMPLE_DEV_PM_OPS(sirfsoc_rtc_pm_ops,
	sirfsoc_rtc_suspend, sirfsoc_rtc_resume);

	static struct platform_driver sirfsoc_rtc_driver = {
	.driver = {
	.name = "sirfsoc-rtc",
	.pm = &sirfsoc_rtc_pm_ops,
	.of_match_table = sirfsoc_rtc_of_match,
	},
	.probe = sirfsoc_rtc_probe,
	};
	module_platform_driver(sirfsoc_rtc_driver);

	MODULE_DESCRIPTION("SiRF SoC rtc driver");
	MODULE_AUTHOR("Xianglong Du <Xianglong.Du@csr.com>");
	MODULE_LICENSE("GPL v2");
	MODULE_ALIAS("platform:sirfsoc-rtc");