drivers/rtc/rtc-imxdi.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
  * Copyright 2010 Orex Computed Radiography
  */

 /*
  * The code contained herein is licensed under the GNU General Public
  * License. You may obtain a copy of the GNU General Public License
  * Version 2 or later at the following locations:
  *
  * http://www.opensource.org/licenses/gpl-license.html
  * http://www.gnu.org/copyleft/gpl.html
  */

 /* based on rtc-mc13892.c */

 /*
  * This driver uses the 47-bit 32 kHz counter in the Freescale DryIce block
  * to implement a Linux RTC. Times and alarms are truncated to seconds.
  * Since the RTC framework performs API locking via rtc->ops_lock the
  * only simultaneous accesses we need to deal with is updating DryIce
  * registers while servicing an alarm.
  *
  * Note that reading the DSR (DryIce Status Register) automatically clears
  * the WCF (Write Complete Flag). All DryIce writes are synchronized to the
  * LP (Low Power) domain and set the WCF upon completion. Writes to the
  * DIER (DryIce Interrupt Enable Register) are the only exception. These
  * occur at normal bus speeds and do not set WCF.  Periodic interrupts are
  * not supported by the hardware.
  */

 #include <linux/io.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/rtc.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 #include <linux/of.h>

 /* DryIce Register Definitions */

 #define DTCMR     0x00           /* Time Counter MSB Reg */
 #define DTCLR     0x04           /* Time Counter LSB Reg */

 #define DCAMR     0x08           /* Clock Alarm MSB Reg */
 #define DCALR     0x0c           /* Clock Alarm LSB Reg */
 #define DCAMR_UNSET  0xFFFFFFFF  /* doomsday - 1 sec */

 #define DCR       0x10           /* Control Reg */
 #define DCR_TCE   (1 << 3)       /* Time Counter Enable */

 #define DSR       0x14           /* Status Reg */
 #define DSR_WBF   (1 << 10)      /* Write Busy Flag */
 #define DSR_WNF   (1 << 9)       /* Write Next Flag */
 #define DSR_WCF   (1 << 8)       /* Write Complete Flag */
 #define DSR_WEF   (1 << 7)       /* Write Error Flag */
 #define DSR_CAF   (1 << 4)       /* Clock Alarm Flag */
 #define DSR_NVF   (1 << 1)       /* Non-Valid Flag */
 #define DSR_SVF   (1 << 0)       /* Security Violation Flag */

 #define DIER      0x18           /* Interrupt Enable Reg */
 #define DIER_WNIE (1 << 9)       /* Write Next Interrupt Enable */
 #define DIER_WCIE (1 << 8)       /* Write Complete Interrupt Enable */
 #define DIER_WEIE (1 << 7)       /* Write Error Interrupt Enable */
 #define DIER_CAIE (1 << 4)       /* Clock Alarm Interrupt Enable */

 /**
  * struct imxdi_dev - private imxdi rtc data
  * @pdev: pionter to platform dev
  * @rtc: pointer to rtc struct
  * @ioaddr: IO registers pointer
  * @irq: dryice normal interrupt
  * @clk: input reference clock
  * @dsr: copy of the DSR register
  * @irq_lock: interrupt enable register (DIER) lock
  * @write_wait: registers write complete queue
  * @write_mutex: serialize registers write
  * @work: schedule alarm work
  */
 struct imxdi_dev {
 	struct platform_device *pdev;
 	struct rtc_device *rtc;
 	void __iomem *ioaddr;
 	int irq;
 	struct clk *clk;
 	u32 dsr;
 	spinlock_t irq_lock;
 	wait_queue_head_t write_wait;
 	struct mutex write_mutex;
 	struct work_struct work;
 };

 /*
  * enable a dryice interrupt
  */
 static void di_int_enable(struct imxdi_dev *imxdi, u32 intr)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&imxdi->irq_lock, flags);
 	__raw_writel(__raw_readl(imxdi->ioaddr + DIER) | intr,
 			imxdi->ioaddr + DIER);
 	spin_unlock_irqrestore(&imxdi->irq_lock, flags);
 }

 /*
  * disable a dryice interrupt
  */
 static void di_int_disable(struct imxdi_dev *imxdi, u32 intr)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&imxdi->irq_lock, flags);
 	__raw_writel(__raw_readl(imxdi->ioaddr + DIER) & ~intr,
 			imxdi->ioaddr + DIER);
 	spin_unlock_irqrestore(&imxdi->irq_lock, flags);
 }

 /*
  * This function attempts to clear the dryice write-error flag.
  *
  * A dryice write error is similar to a bus fault and should not occur in
  * normal operation.  Clearing the flag requires another write, so the root
  * cause of the problem may need to be fixed before the flag can be cleared.
  */
 static void clear_write_error(struct imxdi_dev *imxdi)
 {
 	int cnt;

 	dev_warn(&imxdi->pdev->dev, "WARNING: Register write error!\n");

 	/* clear the write error flag */
 	__raw_writel(DSR_WEF, imxdi->ioaddr + DSR);

 	/* wait for it to take effect */
 	for (cnt = 0; cnt < 1000; cnt++) {
 		if ((__raw_readl(imxdi->ioaddr + DSR) & DSR_WEF) == 0)
 			return;
 		udelay(10);
 	}
 	dev_err(&imxdi->pdev->dev,
 			"ERROR: Cannot clear write-error flag!\n");
 }

 /*
  * Write a dryice register and wait until it completes.
  *
  * This function uses interrupts to determine when the
  * write has completed.
  */
 static int di_write_wait(struct imxdi_dev *imxdi, u32 val, int reg)
 {
 	int ret;
 	int rc = 0;

 	/* serialize register writes */
 	mutex_lock(&imxdi->write_mutex);

 	/* enable the write-complete interrupt */
 	di_int_enable(imxdi, DIER_WCIE);

 	imxdi->dsr = 0;

 	/* do the register write */
 	__raw_writel(val, imxdi->ioaddr + reg);

 	/* wait for the write to finish */
 	ret = wait_event_interruptible_timeout(imxdi->write_wait,
 			imxdi->dsr & (DSR_WCF | DSR_WEF), msecs_to_jiffies(1));
 	if (ret < 0) {
 		rc = ret;
 		goto out;
 	} else if (ret == 0) {
 		dev_warn(&imxdi->pdev->dev,
 				"Write-wait timeout "
 				"val = 0x%08x reg = 0x%08x\n", val, reg);
 	}

 	/* check for write error */
 	if (imxdi->dsr & DSR_WEF) {
 		clear_write_error(imxdi);
 		rc = -EIO;
 	}

 out:
 	mutex_unlock(&imxdi->write_mutex);

 	return rc;
 }

 /*
  * read the seconds portion of the current time from the dryice time counter
  */
 static int dryice_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 	unsigned long now;

 	now = __raw_readl(imxdi->ioaddr + DTCMR);
 	rtc_time_to_tm(now, tm);

 	return 0;
 }

 /*
  * set the seconds portion of dryice time counter and clear the
  * fractional part.
  */
 static int dryice_rtc_set_mmss(struct device *dev, unsigned long secs)
 {
 	struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 	int rc;

 	/* zero the fractional part first */
 	rc = di_write_wait(imxdi, 0, DTCLR);
 	if (rc == 0)
 		rc = di_write_wait(imxdi, secs, DTCMR);

 	return rc;
 }

 static int dryice_rtc_alarm_irq_enable(struct device *dev,
 		unsigned int enabled)
 {
 	struct imxdi_dev *imxdi = dev_get_drvdata(dev);

 	if (enabled)
 		di_int_enable(imxdi, DIER_CAIE);
 	else
 		di_int_disable(imxdi, DIER_CAIE);

 	return 0;
 }

 /*
  * read the seconds portion of the alarm register.
  * the fractional part of the alarm register is always zero.
  */
 static int dryice_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 {
 	struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 	u32 dcamr;

 	dcamr = __raw_readl(imxdi->ioaddr + DCAMR);
 	rtc_time_to_tm(dcamr, &alarm->time);

 	/* alarm is enabled if the interrupt is enabled */
 	alarm->enabled = (__raw_readl(imxdi->ioaddr + DIER) & DIER_CAIE) != 0;

 	/* don't allow the DSR read to mess up DSR_WCF */
 	mutex_lock(&imxdi->write_mutex);

 	/* alarm is pending if the alarm flag is set */
 	alarm->pending = (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) != 0;

 	mutex_unlock(&imxdi->write_mutex);

 	return 0;
 }

 /*
  * set the seconds portion of dryice alarm register
  */
 static int dryice_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 {
 	struct imxdi_dev *imxdi = dev_get_drvdata(dev);
 	unsigned long now;
 	unsigned long alarm_time;
 	int rc;

 	rc = rtc_tm_to_time(&alarm->time, &alarm_time);
 	if (rc)
 		return rc;

 	/* don't allow setting alarm in the past */
 	now = __raw_readl(imxdi->ioaddr + DTCMR);
 	if (alarm_time < now)
 		return -EINVAL;

 	/* write the new alarm time */
 	rc = di_write_wait(imxdi, (u32)alarm_time, DCAMR);
 	if (rc)
 		return rc;

 	if (alarm->enabled)
 		di_int_enable(imxdi, DIER_CAIE);  /* enable alarm intr */
 	else
 		di_int_disable(imxdi, DIER_CAIE); /* disable alarm intr */

 	return 0;
 }

 static struct rtc_class_ops dryice_rtc_ops = {
 	.read_time		= dryice_rtc_read_time,
 	.set_mmss		= dryice_rtc_set_mmss,
 	.alarm_irq_enable	= dryice_rtc_alarm_irq_enable,
 	.read_alarm		= dryice_rtc_read_alarm,
 	.set_alarm		= dryice_rtc_set_alarm,
 };

 /*
  * dryice "normal" interrupt handler
  */
 static irqreturn_t dryice_norm_irq(int irq, void *dev_id)
 {
 	struct imxdi_dev *imxdi = dev_id;
 	u32 dsr, dier;
 	irqreturn_t rc = IRQ_NONE;

 	dier = __raw_readl(imxdi->ioaddr + DIER);

 	/* handle write complete and write error cases */
 	if ((dier & DIER_WCIE)) {
 		/*If the write wait queue is empty then there is no pending
 		  operations. It means the interrupt is for DryIce -Security.
 		  IRQ must be returned as none.*/
 		if (list_empty_careful(&imxdi->write_wait.task_list))
 			return rc;

 		/* DSR_WCF clears itself on DSR read */
 		dsr = __raw_readl(imxdi->ioaddr + DSR);
 		if ((dsr & (DSR_WCF | DSR_WEF))) {
 			/* mask the interrupt */
 			di_int_disable(imxdi, DIER_WCIE);

 			/* save the dsr value for the wait queue */
 			imxdi->dsr |= dsr;

 			wake_up_interruptible(&imxdi->write_wait);
 			rc = IRQ_HANDLED;
 		}
 	}

 	/* handle the alarm case */
 	if ((dier & DIER_CAIE)) {
 		/* DSR_WCF clears itself on DSR read */
 		dsr = __raw_readl(imxdi->ioaddr + DSR);
 		if (dsr & DSR_CAF) {
 			/* mask the interrupt */
 			di_int_disable(imxdi, DIER_CAIE);

 			/* finish alarm in user context */
 			schedule_work(&imxdi->work);
 			rc = IRQ_HANDLED;
 		}
 	}
 	return rc;
 }

 /*
  * post the alarm event from user context so it can sleep
  * on the write completion.
  */
 static void dryice_work(struct work_struct *work)
 {
 	struct imxdi_dev *imxdi = container_of(work,
 			struct imxdi_dev, work);

 	/* dismiss the interrupt (ignore error) */
 	di_write_wait(imxdi, DSR_CAF, DSR);

 	/* pass the alarm event to the rtc framework. */
 	rtc_update_irq(imxdi->rtc, 1, RTC_AF | RTC_IRQF);
 }

 /*
  * probe for dryice rtc device
  */
 static int __init dryice_rtc_probe(struct platform_device *pdev)
 {
 	struct resource *res;
 	struct imxdi_dev *imxdi;
 	int rc;

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

 	imxdi->pdev = pdev;

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

 	spin_lock_init(&imxdi->irq_lock);

 	imxdi->irq = platform_get_irq(pdev, 0);
 	if (imxdi->irq < 0)
 		return imxdi->irq;

 	init_waitqueue_head(&imxdi->write_wait);

 	INIT_WORK(&imxdi->work, dryice_work);

 	mutex_init(&imxdi->write_mutex);

 	imxdi->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(imxdi->clk))
 		return PTR_ERR(imxdi->clk);
 	clk_prepare_enable(imxdi->clk);

 	/*
 	 * Initialize dryice hardware
 	 */

 	/* mask all interrupts */
 	__raw_writel(0, imxdi->ioaddr + DIER);

 	rc = devm_request_irq(&pdev->dev, imxdi->irq, dryice_norm_irq,
 			IRQF_SHARED, pdev->name, imxdi);
 	if (rc) {
 		dev_warn(&pdev->dev, "interrupt not available.\n");
 		goto err;
 	}

 	/* put dryice into valid state */
 	if (__raw_readl(imxdi->ioaddr + DSR) & DSR_NVF) {
 		rc = di_write_wait(imxdi, DSR_NVF | DSR_SVF, DSR);
 		if (rc)
 			goto err;
 	}

 	/* initialize alarm */
 	rc = di_write_wait(imxdi, DCAMR_UNSET, DCAMR);
 	if (rc)
 		goto err;
 	rc = di_write_wait(imxdi, 0, DCALR);
 	if (rc)
 		goto err;

 	/* clear alarm flag */
 	if (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) {
 		rc = di_write_wait(imxdi, DSR_CAF, DSR);
 		if (rc)
 			goto err;
 	}

 	/* the timer won't count if it has never been written to */
 	if (__raw_readl(imxdi->ioaddr + DTCMR) == 0) {
 		rc = di_write_wait(imxdi, 0, DTCMR);
 		if (rc)
 			goto err;
 	}

 	/* start keeping time */
 	if (!(__raw_readl(imxdi->ioaddr + DCR) & DCR_TCE)) {
 		rc = di_write_wait(imxdi,
 				__raw_readl(imxdi->ioaddr + DCR) | DCR_TCE,
 				DCR);
 		if (rc)
 			goto err;
 	}

 	platform_set_drvdata(pdev, imxdi);
 	imxdi->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
 				  &dryice_rtc_ops, THIS_MODULE);
 	if (IS_ERR(imxdi->rtc)) {
 		rc = PTR_ERR(imxdi->rtc);
 		goto err;
 	}

 	return 0;

 err:
 	clk_disable_unprepare(imxdi->clk);

 	return rc;
 }

 static int __exit dryice_rtc_remove(struct platform_device *pdev)
 {
 	struct imxdi_dev *imxdi = platform_get_drvdata(pdev);

 	flush_work(&imxdi->work);

 	/* mask all interrupts */
 	__raw_writel(0, imxdi->ioaddr + DIER);

 	clk_disable_unprepare(imxdi->clk);

 	return 0;
 }

 #ifdef CONFIG_OF
 static const struct of_device_id dryice_dt_ids[] = {
 	{ .compatible = "fsl,imx25-rtc" },
 	{ /* sentinel */ }
 };

 MODULE_DEVICE_TABLE(of, dryice_dt_ids);
 #endif

 static struct platform_driver dryice_rtc_driver = {
 	.driver = {
 		   .name = "imxdi_rtc",
 		   .owner = THIS_MODULE,
 		   .of_match_table = of_match_ptr(dryice_dt_ids),
 		   },
 	.remove = __exit_p(dryice_rtc_remove),
 };

 module_platform_driver_probe(dryice_rtc_driver, dryice_rtc_probe);

 MODULE_AUTHOR("Freescale Semiconductor, Inc.");
 MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
 MODULE_DESCRIPTION("IMX DryIce Realtime Clock Driver (RTC)");
 MODULE_LICENSE("GPL");
	/*
	* Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
	* Copyright 2010 Orex Computed Radiography
	*/

	/*
	* The code contained herein is licensed under the GNU General Public
	* License. You may obtain a copy of the GNU General Public License
	* Version 2 or later at the following locations:
	*
	* http://www.opensource.org/licenses/gpl-license.html
	* http://www.gnu.org/copyleft/gpl.html
	*/

	/* based on rtc-mc13892.c */

	/*
	* This driver uses the 47-bit 32 kHz counter in the Freescale DryIce block
	* to implement a Linux RTC. Times and alarms are truncated to seconds.
	* Since the RTC framework performs API locking via rtc->ops_lock the
	* only simultaneous accesses we need to deal with is updating DryIce
	* registers while servicing an alarm.
	*
	* Note that reading the DSR (DryIce Status Register) automatically clears
	* the WCF (Write Complete Flag). All DryIce writes are synchronized to the
	* LP (Low Power) domain and set the WCF upon completion. Writes to the
	* DIER (DryIce Interrupt Enable Register) are the only exception. These
	* occur at normal bus speeds and do not set WCF. Periodic interrupts are
	* not supported by the hardware.
	*/

	#include <linux/io.h>
	#include <linux/clk.h>
	#include <linux/delay.h>
	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/rtc.h>
	#include <linux/sched.h>
	#include <linux/spinlock.h>
	#include <linux/workqueue.h>
	#include <linux/of.h>

	/* DryIce Register Definitions */

	#define DTCMR 0x00 /* Time Counter MSB Reg */
	#define DTCLR 0x04 /* Time Counter LSB Reg */

	#define DCAMR 0x08 /* Clock Alarm MSB Reg */
	#define DCALR 0x0c /* Clock Alarm LSB Reg */
	#define DCAMR_UNSET 0xFFFFFFFF /* doomsday - 1 sec */

	#define DCR 0x10 /* Control Reg */
	#define DCR_TCE (1 << 3) /* Time Counter Enable */

	#define DSR 0x14 /* Status Reg */
	#define DSR_WBF (1 << 10) /* Write Busy Flag */
	#define DSR_WNF (1 << 9) /* Write Next Flag */
	#define DSR_WCF (1 << 8) /* Write Complete Flag */
	#define DSR_WEF (1 << 7) /* Write Error Flag */
	#define DSR_CAF (1 << 4) /* Clock Alarm Flag */
	#define DSR_NVF (1 << 1) /* Non-Valid Flag */
	#define DSR_SVF (1 << 0) /* Security Violation Flag */

	#define DIER 0x18 /* Interrupt Enable Reg */
	#define DIER_WNIE (1 << 9) /* Write Next Interrupt Enable */
	#define DIER_WCIE (1 << 8) /* Write Complete Interrupt Enable */
	#define DIER_WEIE (1 << 7) /* Write Error Interrupt Enable */
	#define DIER_CAIE (1 << 4) /* Clock Alarm Interrupt Enable */

	/**
	* struct imxdi_dev - private imxdi rtc data
	* @pdev: pionter to platform dev
	* @rtc: pointer to rtc struct
	* @ioaddr: IO registers pointer
	* @irq: dryice normal interrupt
	* @clk: input reference clock
	* @dsr: copy of the DSR register
	* @irq_lock: interrupt enable register (DIER) lock
	* @write_wait: registers write complete queue
	* @write_mutex: serialize registers write
	* @work: schedule alarm work
	*/
	struct imxdi_dev {
	struct platform_device *pdev;
	struct rtc_device *rtc;
	void __iomem *ioaddr;
	int irq;
	struct clk *clk;
	u32 dsr;
	spinlock_t irq_lock;
	wait_queue_head_t write_wait;
	struct mutex write_mutex;
	struct work_struct work;
	};

	/*
	* enable a dryice interrupt
	*/
	static void di_int_enable(struct imxdi_dev *imxdi, u32 intr)
	{
	unsigned long flags;

	spin_lock_irqsave(&imxdi->irq_lock, flags);
	__raw_writel(__raw_readl(imxdi->ioaddr + DIER) \| intr,
	imxdi->ioaddr + DIER);
	spin_unlock_irqrestore(&imxdi->irq_lock, flags);
	}

	/*
	* disable a dryice interrupt
	*/
	static void di_int_disable(struct imxdi_dev *imxdi, u32 intr)
	{
	unsigned long flags;

	spin_lock_irqsave(&imxdi->irq_lock, flags);
	__raw_writel(__raw_readl(imxdi->ioaddr + DIER) & ~intr,
	imxdi->ioaddr + DIER);
	spin_unlock_irqrestore(&imxdi->irq_lock, flags);
	}

	/*
	* This function attempts to clear the dryice write-error flag.
	*
	* A dryice write error is similar to a bus fault and should not occur in
	* normal operation. Clearing the flag requires another write, so the root
	* cause of the problem may need to be fixed before the flag can be cleared.
	*/
	static void clear_write_error(struct imxdi_dev *imxdi)
	{
	int cnt;

	dev_warn(&imxdi->pdev->dev, "WARNING: Register write error!\n");

	/* clear the write error flag */
	__raw_writel(DSR_WEF, imxdi->ioaddr + DSR);

	/* wait for it to take effect */
	for (cnt = 0; cnt < 1000; cnt++) {
	if ((__raw_readl(imxdi->ioaddr + DSR) & DSR_WEF) == 0)
	return;
	udelay(10);
	}
	dev_err(&imxdi->pdev->dev,
	"ERROR: Cannot clear write-error flag!\n");
	}

	/*
	* Write a dryice register and wait until it completes.
	*
	* This function uses interrupts to determine when the
	* write has completed.
	*/
	static int di_write_wait(struct imxdi_dev *imxdi, u32 val, int reg)
	{
	int ret;
	int rc = 0;

	/* serialize register writes */
	mutex_lock(&imxdi->write_mutex);

	/* enable the write-complete interrupt */
	di_int_enable(imxdi, DIER_WCIE);

	imxdi->dsr = 0;

	/* do the register write */
	__raw_writel(val, imxdi->ioaddr + reg);

	/* wait for the write to finish */
	ret = wait_event_interruptible_timeout(imxdi->write_wait,
	imxdi->dsr & (DSR_WCF \| DSR_WEF), msecs_to_jiffies(1));
	if (ret < 0) {
	rc = ret;
	goto out;
	} else if (ret == 0) {
	dev_warn(&imxdi->pdev->dev,
	"Write-wait timeout "
	"val = 0x%08x reg = 0x%08x\n", val, reg);
	}

	/* check for write error */
	if (imxdi->dsr & DSR_WEF) {
	clear_write_error(imxdi);
	rc = -EIO;
	}

	out:
	mutex_unlock(&imxdi->write_mutex);

	return rc;
	}

	/*
	* read the seconds portion of the current time from the dryice time counter
	*/
	static int dryice_rtc_read_time(struct device dev, struct rtc_time tm)
	{
	struct imxdi_dev *imxdi = dev_get_drvdata(dev);
	unsigned long now;

	now = __raw_readl(imxdi->ioaddr + DTCMR);
	rtc_time_to_tm(now, tm);

	return 0;
	}

	/*
	* set the seconds portion of dryice time counter and clear the
	* fractional part.
	*/
	static int dryice_rtc_set_mmss(struct device *dev, unsigned long secs)
	{
	struct imxdi_dev *imxdi = dev_get_drvdata(dev);
	int rc;

	/* zero the fractional part first */
	rc = di_write_wait(imxdi, 0, DTCLR);
	if (rc == 0)
	rc = di_write_wait(imxdi, secs, DTCMR);

	return rc;
	}

	static int dryice_rtc_alarm_irq_enable(struct device *dev,
	unsigned int enabled)
	{
	struct imxdi_dev *imxdi = dev_get_drvdata(dev);

	if (enabled)
	di_int_enable(imxdi, DIER_CAIE);
	else
	di_int_disable(imxdi, DIER_CAIE);

	return 0;
	}

	/*
	* read the seconds portion of the alarm register.
	* the fractional part of the alarm register is always zero.
	*/
	static int dryice_rtc_read_alarm(struct device dev, struct rtc_wkalrm alarm)
	{
	struct imxdi_dev *imxdi = dev_get_drvdata(dev);
	u32 dcamr;

	dcamr = __raw_readl(imxdi->ioaddr + DCAMR);
	rtc_time_to_tm(dcamr, &alarm->time);

	/* alarm is enabled if the interrupt is enabled */
	alarm->enabled = (__raw_readl(imxdi->ioaddr + DIER) & DIER_CAIE) != 0;

	/* don't allow the DSR read to mess up DSR_WCF */
	mutex_lock(&imxdi->write_mutex);

	/* alarm is pending if the alarm flag is set */
	alarm->pending = (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) != 0;

	mutex_unlock(&imxdi->write_mutex);

	return 0;
	}

	/*
	* set the seconds portion of dryice alarm register
	*/
	static int dryice_rtc_set_alarm(struct device dev, struct rtc_wkalrm alarm)
	{
	struct imxdi_dev *imxdi = dev_get_drvdata(dev);
	unsigned long now;
	unsigned long alarm_time;
	int rc;

	rc = rtc_tm_to_time(&alarm->time, &alarm_time);
	if (rc)
	return rc;

	/* don't allow setting alarm in the past */
	now = __raw_readl(imxdi->ioaddr + DTCMR);
	if (alarm_time < now)
	return -EINVAL;

	/* write the new alarm time */
	rc = di_write_wait(imxdi, (u32)alarm_time, DCAMR);
	if (rc)
	return rc;

	if (alarm->enabled)
	di_int_enable(imxdi, DIER_CAIE); /* enable alarm intr */
	else
	di_int_disable(imxdi, DIER_CAIE); /* disable alarm intr */

	return 0;
	}

	static struct rtc_class_ops dryice_rtc_ops = {
	.read_time = dryice_rtc_read_time,
	.set_mmss = dryice_rtc_set_mmss,
	.alarm_irq_enable = dryice_rtc_alarm_irq_enable,
	.read_alarm = dryice_rtc_read_alarm,
	.set_alarm = dryice_rtc_set_alarm,
	};

	/*
	* dryice "normal" interrupt handler
	*/
	static irqreturn_t dryice_norm_irq(int irq, void *dev_id)
	{
	struct imxdi_dev *imxdi = dev_id;
	u32 dsr, dier;
	irqreturn_t rc = IRQ_NONE;

	dier = __raw_readl(imxdi->ioaddr + DIER);

	/* handle write complete and write error cases */
	if ((dier & DIER_WCIE)) {
	/*If the write wait queue is empty then there is no pending
	operations. It means the interrupt is for DryIce -Security.
	IRQ must be returned as none.*/
	if (list_empty_careful(&imxdi->write_wait.task_list))
	return rc;

	/* DSR_WCF clears itself on DSR read */
	dsr = __raw_readl(imxdi->ioaddr + DSR);
	if ((dsr & (DSR_WCF \| DSR_WEF))) {
	/* mask the interrupt */
	di_int_disable(imxdi, DIER_WCIE);

	/* save the dsr value for the wait queue */
	imxdi->dsr \|= dsr;

	wake_up_interruptible(&imxdi->write_wait);
	rc = IRQ_HANDLED;
	}
	}

	/* handle the alarm case */
	if ((dier & DIER_CAIE)) {
	/* DSR_WCF clears itself on DSR read */
	dsr = __raw_readl(imxdi->ioaddr + DSR);
	if (dsr & DSR_CAF) {
	/* mask the interrupt */
	di_int_disable(imxdi, DIER_CAIE);

	/* finish alarm in user context */
	schedule_work(&imxdi->work);
	rc = IRQ_HANDLED;
	}
	}
	return rc;
	}

	/*
	* post the alarm event from user context so it can sleep
	* on the write completion.
	*/
	static void dryice_work(struct work_struct *work)
	{
	struct imxdi_dev *imxdi = container_of(work,
	struct imxdi_dev, work);

	/* dismiss the interrupt (ignore error) */
	di_write_wait(imxdi, DSR_CAF, DSR);

	/* pass the alarm event to the rtc framework. */
	rtc_update_irq(imxdi->rtc, 1, RTC_AF \| RTC_IRQF);
	}

	/*
	* probe for dryice rtc device
	*/
	static int __init dryice_rtc_probe(struct platform_device *pdev)
	{
	struct resource *res;
	struct imxdi_dev *imxdi;
	int rc;

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

	imxdi->pdev = pdev;

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

	spin_lock_init(&imxdi->irq_lock);

	imxdi->irq = platform_get_irq(pdev, 0);
	if (imxdi->irq < 0)
	return imxdi->irq;

	init_waitqueue_head(&imxdi->write_wait);

	INIT_WORK(&imxdi->work, dryice_work);

	mutex_init(&imxdi->write_mutex);

	imxdi->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(imxdi->clk))
	return PTR_ERR(imxdi->clk);
	clk_prepare_enable(imxdi->clk);

	/*
	* Initialize dryice hardware
	*/

	/* mask all interrupts */
	__raw_writel(0, imxdi->ioaddr + DIER);

	rc = devm_request_irq(&pdev->dev, imxdi->irq, dryice_norm_irq,
	IRQF_SHARED, pdev->name, imxdi);
	if (rc) {
	dev_warn(&pdev->dev, "interrupt not available.\n");
	goto err;
	}

	/* put dryice into valid state */
	if (__raw_readl(imxdi->ioaddr + DSR) & DSR_NVF) {
	rc = di_write_wait(imxdi, DSR_NVF \| DSR_SVF, DSR);
	if (rc)
	goto err;
	}

	/* initialize alarm */
	rc = di_write_wait(imxdi, DCAMR_UNSET, DCAMR);
	if (rc)
	goto err;
	rc = di_write_wait(imxdi, 0, DCALR);
	if (rc)
	goto err;

	/* clear alarm flag */
	if (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) {
	rc = di_write_wait(imxdi, DSR_CAF, DSR);
	if (rc)
	goto err;
	}

	/* the timer won't count if it has never been written to */
	if (__raw_readl(imxdi->ioaddr + DTCMR) == 0) {
	rc = di_write_wait(imxdi, 0, DTCMR);
	if (rc)
	goto err;
	}

	/* start keeping time */
	if (!(__raw_readl(imxdi->ioaddr + DCR) & DCR_TCE)) {
	rc = di_write_wait(imxdi,
	__raw_readl(imxdi->ioaddr + DCR) \| DCR_TCE,
	DCR);
	if (rc)
	goto err;
	}

	platform_set_drvdata(pdev, imxdi);
	imxdi->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
	&dryice_rtc_ops, THIS_MODULE);
	if (IS_ERR(imxdi->rtc)) {
	rc = PTR_ERR(imxdi->rtc);
	goto err;
	}

	return 0;

	err:
	clk_disable_unprepare(imxdi->clk);

	return rc;
	}

	static int __exit dryice_rtc_remove(struct platform_device *pdev)
	{
	struct imxdi_dev *imxdi = platform_get_drvdata(pdev);

	flush_work(&imxdi->work);

	/* mask all interrupts */
	__raw_writel(0, imxdi->ioaddr + DIER);

	clk_disable_unprepare(imxdi->clk);

	return 0;
	}

	#ifdef CONFIG_OF
	static const struct of_device_id dryice_dt_ids[] = {
	{ .compatible = "fsl,imx25-rtc" },
	{ /* sentinel */ }
	};

	MODULE_DEVICE_TABLE(of, dryice_dt_ids);
	#endif

	static struct platform_driver dryice_rtc_driver = {
	.driver = {
	.name = "imxdi_rtc",
	.owner = THIS_MODULE,
	.of_match_table = of_match_ptr(dryice_dt_ids),
	},
	.remove = __exit_p(dryice_rtc_remove),
	};

	module_platform_driver_probe(dryice_rtc_driver, dryice_rtc_probe);

	MODULE_AUTHOR("Freescale Semiconductor, Inc.");
	MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
	MODULE_DESCRIPTION("IMX DryIce Realtime Clock Driver (RTC)");
	MODULE_LICENSE("GPL");