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

 /*
  * An RTC driver for the NVIDIA Tegra 200 series internal RTC.
  *
  * Copyright (c) 2010, NVIDIA Corporation.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  * more details.
  *
  * You should have received a copy of the GNU General Public License along
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */

 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/irq.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/platform_device.h>
 #include <linux/pm.h>
 #include <linux/rtc.h>
 #include <linux/slab.h>

 /* set to 1 = busy every eight 32kHz clocks during copy of sec+msec to AHB */
 #define TEGRA_RTC_REG_BUSY			0x004
 #define TEGRA_RTC_REG_SECONDS			0x008
 /* when msec is read, the seconds are buffered into shadow seconds. */
 #define TEGRA_RTC_REG_SHADOW_SECONDS		0x00c
 #define TEGRA_RTC_REG_MILLI_SECONDS		0x010
 #define TEGRA_RTC_REG_SECONDS_ALARM0		0x014
 #define TEGRA_RTC_REG_SECONDS_ALARM1		0x018
 #define TEGRA_RTC_REG_MILLI_SECONDS_ALARM0	0x01c
 #define TEGRA_RTC_REG_INTR_MASK			0x028
 /* write 1 bits to clear status bits */
 #define TEGRA_RTC_REG_INTR_STATUS		0x02c

 /* bits in INTR_MASK */
 #define TEGRA_RTC_INTR_MASK_MSEC_CDN_ALARM	(1<<4)
 #define TEGRA_RTC_INTR_MASK_SEC_CDN_ALARM	(1<<3)
 #define TEGRA_RTC_INTR_MASK_MSEC_ALARM		(1<<2)
 #define TEGRA_RTC_INTR_MASK_SEC_ALARM1		(1<<1)
 #define TEGRA_RTC_INTR_MASK_SEC_ALARM0		(1<<0)

 /* bits in INTR_STATUS */
 #define TEGRA_RTC_INTR_STATUS_MSEC_CDN_ALARM	(1<<4)
 #define TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM	(1<<3)
 #define TEGRA_RTC_INTR_STATUS_MSEC_ALARM	(1<<2)
 #define TEGRA_RTC_INTR_STATUS_SEC_ALARM1	(1<<1)
 #define TEGRA_RTC_INTR_STATUS_SEC_ALARM0	(1<<0)

 struct tegra_rtc_info {
 	struct platform_device	*pdev;
 	struct rtc_device	*rtc_dev;
 	void __iomem		*rtc_base; /* NULL if not initialized. */
 	struct clk		*clk;
 	int			tegra_rtc_irq; /* alarm and periodic irq */
 	spinlock_t		tegra_rtc_lock;
 };

 /* RTC hardware is busy when it is updating its values over AHB once
  * every eight 32kHz clocks (~250uS).
  * outside of these updates the CPU is free to write.
  * CPU is always free to read.
  */
 static inline u32 tegra_rtc_check_busy(struct tegra_rtc_info *info)
 {
 	return readl(info->rtc_base + TEGRA_RTC_REG_BUSY) & 1;
 }

 /* Wait for hardware to be ready for writing.
  * This function tries to maximize the amount of time before the next update.
  * It does this by waiting for the RTC to become busy with its periodic update,
  * then returning once the RTC first becomes not busy.
  * This periodic update (where the seconds and milliseconds are copied to the
  * AHB side) occurs every eight 32kHz clocks (~250uS).
  * The behavior of this function allows us to make some assumptions without
  * introducing a race, because 250uS is plenty of time to read/write a value.
  */
 static int tegra_rtc_wait_while_busy(struct device *dev)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);

 	int retries = 500; /* ~490 us is the worst case, ~250 us is best. */

 	/* first wait for the RTC to become busy. this is when it
 	 * posts its updated seconds+msec registers to AHB side. */
 	while (tegra_rtc_check_busy(info)) {
 		if (!retries--)
 			goto retry_failed;
 		udelay(1);
 	}

 	/* now we have about 250 us to manipulate registers */
 	return 0;

 retry_failed:
 	dev_err(dev, "write failed:retry count exceeded.\n");
 	return -ETIMEDOUT;
 }

 static int tegra_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);
 	unsigned long sec, msec;
 	unsigned long sl_irq_flags;

 	/* RTC hardware copies seconds to shadow seconds when a read
 	 * of milliseconds occurs. use a lock to keep other threads out. */
 	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);

 	msec = readl(info->rtc_base + TEGRA_RTC_REG_MILLI_SECONDS);
 	sec = readl(info->rtc_base + TEGRA_RTC_REG_SHADOW_SECONDS);

 	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);

 	rtc_time_to_tm(sec, tm);

 	dev_vdbg(dev, "time read as %lu. %d/%d/%d %d:%02u:%02u\n",
 		sec,
 		tm->tm_mon + 1,
 		tm->tm_mday,
 		tm->tm_year + 1900,
 		tm->tm_hour,
 		tm->tm_min,
 		tm->tm_sec
 	);

 	return 0;
 }

 static int tegra_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);
 	unsigned long sec;
 	int ret;

 	/* convert tm to seconds. */
 	rtc_tm_to_time(tm, &sec);

 	dev_vdbg(dev, "time set to %lu. %d/%d/%d %d:%02u:%02u\n",
 		sec,
 		tm->tm_mon+1,
 		tm->tm_mday,
 		tm->tm_year+1900,
 		tm->tm_hour,
 		tm->tm_min,
 		tm->tm_sec
 	);

 	/* seconds only written if wait succeeded. */
 	ret = tegra_rtc_wait_while_busy(dev);
 	if (!ret)
 		writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS);

 	dev_vdbg(dev, "time read back as %d\n",
 		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS));

 	return ret;
 }

 static int tegra_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);
 	unsigned long sec;
 	unsigned tmp;

 	sec = readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);

 	if (sec == 0) {
 		/* alarm is disabled. */
 		alarm->enabled = 0;
 	} else {
 		/* alarm is enabled. */
 		alarm->enabled = 1;
 		rtc_time_to_tm(sec, &alarm->time);
 	}

 	tmp = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 	alarm->pending = (tmp & TEGRA_RTC_INTR_STATUS_SEC_ALARM0) != 0;

 	return 0;
 }

 static int tegra_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);
 	unsigned status;
 	unsigned long sl_irq_flags;

 	tegra_rtc_wait_while_busy(dev);
 	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);

 	/* read the original value, and OR in the flag. */
 	status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
 	if (enabled)
 		status |= TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* set it */
 	else
 		status &= ~TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* clear it */

 	writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);

 	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);

 	return 0;
 }

 static int tegra_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);
 	unsigned long sec;

 	if (alarm->enabled)
 		rtc_tm_to_time(&alarm->time, &sec);
 	else
 		sec = 0;

 	tegra_rtc_wait_while_busy(dev);
 	writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
 	dev_vdbg(dev, "alarm read back as %d\n",
 		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));

 	/* if successfully written and alarm is enabled ... */
 	if (sec) {
 		tegra_rtc_alarm_irq_enable(dev, 1);

 		dev_vdbg(dev, "alarm set as %lu. %d/%d/%d %d:%02u:%02u\n",
 			sec,
 			alarm->time.tm_mon+1,
 			alarm->time.tm_mday,
 			alarm->time.tm_year+1900,
 			alarm->time.tm_hour,
 			alarm->time.tm_min,
 			alarm->time.tm_sec);
 	} else {
 		/* disable alarm if 0 or write error. */
 		dev_vdbg(dev, "alarm disabled\n");
 		tegra_rtc_alarm_irq_enable(dev, 0);
 	}

 	return 0;
 }

 static int tegra_rtc_proc(struct device *dev, struct seq_file *seq)
 {
 	if (!dev || !dev->driver)
 		return 0;

 	seq_printf(seq, "name\t\t: %s\n", dev_name(dev));

 	return 0;
 }

 static irqreturn_t tegra_rtc_irq_handler(int irq, void *data)
 {
 	struct device *dev = data;
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);
 	unsigned long events = 0;
 	unsigned status;
 	unsigned long sl_irq_flags;

 	status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 	if (status) {
 		/* clear the interrupt masks and status on any irq. */
 		tegra_rtc_wait_while_busy(dev);
 		spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
 		writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
 		writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 		spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
 	}

 	/* check if Alarm */
 	if ((status & TEGRA_RTC_INTR_STATUS_SEC_ALARM0))
 		events |= RTC_IRQF | RTC_AF;

 	/* check if Periodic */
 	if ((status & TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM))
 		events |= RTC_IRQF | RTC_PF;

 	rtc_update_irq(info->rtc_dev, 1, events);

 	return IRQ_HANDLED;
 }

 static const struct rtc_class_ops tegra_rtc_ops = {
 	.read_time	= tegra_rtc_read_time,
 	.set_time	= tegra_rtc_set_time,
 	.read_alarm	= tegra_rtc_read_alarm,
 	.set_alarm	= tegra_rtc_set_alarm,
 	.proc		= tegra_rtc_proc,
 	.alarm_irq_enable = tegra_rtc_alarm_irq_enable,
 };

 static const struct of_device_id tegra_rtc_dt_match[] = {
 	{ .compatible = "nvidia,tegra20-rtc", },
 	{}
 };
 MODULE_DEVICE_TABLE(of, tegra_rtc_dt_match);

 static int __init tegra_rtc_probe(struct platform_device *pdev)
 {
 	struct tegra_rtc_info *info;
 	struct resource *res;
 	int ret;

 	info = devm_kzalloc(&pdev->dev, sizeof(struct tegra_rtc_info),
 		GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;

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

 	ret = platform_get_irq(pdev, 0);
 	if (ret <= 0) {
 		dev_err(&pdev->dev, "failed to get platform IRQ: %d\n", ret);
 		return ret;
 	}

 	info->tegra_rtc_irq = ret;

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

 	ret = clk_prepare_enable(info->clk);
 	if (ret < 0)
 		return ret;

 	/* set context info. */
 	info->pdev = pdev;
 	spin_lock_init(&info->tegra_rtc_lock);

 	platform_set_drvdata(pdev, info);

 	/* clear out the hardware. */
 	writel(0, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
 	writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 	writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);

 	device_init_wakeup(&pdev->dev, 1);

 	info->rtc_dev = devm_rtc_device_register(&pdev->dev,
 				dev_name(&pdev->dev), &tegra_rtc_ops,
 				THIS_MODULE);
 	if (IS_ERR(info->rtc_dev)) {
 		ret = PTR_ERR(info->rtc_dev);
 		dev_err(&pdev->dev, "Unable to register device (err=%d).\n",
 			ret);
 		goto disable_clk;
 	}

 	ret = devm_request_irq(&pdev->dev, info->tegra_rtc_irq,
 			tegra_rtc_irq_handler, IRQF_TRIGGER_HIGH,
 			dev_name(&pdev->dev), &pdev->dev);
 	if (ret) {
 		dev_err(&pdev->dev,
 			"Unable to request interrupt for device (err=%d).\n",
 			ret);
 		goto disable_clk;
 	}

 	dev_notice(&pdev->dev, "Tegra internal Real Time Clock\n");

 	return 0;

 disable_clk:
 	clk_disable_unprepare(info->clk);
 	return ret;
 }

 static int tegra_rtc_remove(struct platform_device *pdev)
 {
 	struct tegra_rtc_info *info = platform_get_drvdata(pdev);

 	clk_disable_unprepare(info->clk);

 	return 0;
 }

 #ifdef CONFIG_PM_SLEEP
 static int tegra_rtc_suspend(struct device *dev)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);

 	tegra_rtc_wait_while_busy(dev);

 	/* only use ALARM0 as a wake source. */
 	writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
 	writel(TEGRA_RTC_INTR_STATUS_SEC_ALARM0,
 		info->rtc_base + TEGRA_RTC_REG_INTR_MASK);

 	dev_vdbg(dev, "alarm sec = %d\n",
 		readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));

 	dev_vdbg(dev, "Suspend (device_may_wakeup=%d) irq:%d\n",
 		device_may_wakeup(dev), info->tegra_rtc_irq);

 	/* leave the alarms on as a wake source. */
 	if (device_may_wakeup(dev))
 		enable_irq_wake(info->tegra_rtc_irq);

 	return 0;
 }

 static int tegra_rtc_resume(struct device *dev)
 {
 	struct tegra_rtc_info *info = dev_get_drvdata(dev);

 	dev_vdbg(dev, "Resume (device_may_wakeup=%d)\n",
 		device_may_wakeup(dev));
 	/* alarms were left on as a wake source, turn them off. */
 	if (device_may_wakeup(dev))
 		disable_irq_wake(info->tegra_rtc_irq);

 	return 0;
 }
 #endif

 static SIMPLE_DEV_PM_OPS(tegra_rtc_pm_ops, tegra_rtc_suspend, tegra_rtc_resume);

 static void tegra_rtc_shutdown(struct platform_device *pdev)
 {
 	dev_vdbg(&pdev->dev, "disabling interrupts.\n");
 	tegra_rtc_alarm_irq_enable(&pdev->dev, 0);
 }

 MODULE_ALIAS("platform:tegra_rtc");
 static struct platform_driver tegra_rtc_driver = {
 	.remove		= tegra_rtc_remove,
 	.shutdown	= tegra_rtc_shutdown,
 	.driver		= {
 		.name	= "tegra_rtc",
 		.of_match_table = tegra_rtc_dt_match,
 		.pm	= &tegra_rtc_pm_ops,
 	},
 };

 module_platform_driver_probe(tegra_rtc_driver, tegra_rtc_probe);

 MODULE_AUTHOR("Jon Mayo <jmayo@nvidia.com>");
 MODULE_DESCRIPTION("driver for Tegra internal RTC");
 MODULE_LICENSE("GPL");
	/*
	* An RTC driver for the NVIDIA Tegra 200 series internal RTC.
	*
	* Copyright (c) 2010, NVIDIA Corporation.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
	* more details.
	*
	* You should have received a copy of the GNU General Public License along
	* with this program; if not, write to the Free Software Foundation, Inc.,
	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
	*/

	#include <linux/clk.h>
	#include <linux/delay.h>
	#include <linux/init.h>
	#include <linux/io.h>
	#include <linux/irq.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/mod_devicetable.h>
	#include <linux/platform_device.h>
	#include <linux/pm.h>
	#include <linux/rtc.h>
	#include <linux/slab.h>

	/* set to 1 = busy every eight 32kHz clocks during copy of sec+msec to AHB */
	#define TEGRA_RTC_REG_BUSY 0x004
	#define TEGRA_RTC_REG_SECONDS 0x008
	/* when msec is read, the seconds are buffered into shadow seconds. */
	#define TEGRA_RTC_REG_SHADOW_SECONDS 0x00c
	#define TEGRA_RTC_REG_MILLI_SECONDS 0x010
	#define TEGRA_RTC_REG_SECONDS_ALARM0 0x014
	#define TEGRA_RTC_REG_SECONDS_ALARM1 0x018
	#define TEGRA_RTC_REG_MILLI_SECONDS_ALARM0 0x01c
	#define TEGRA_RTC_REG_INTR_MASK 0x028
	/* write 1 bits to clear status bits */
	#define TEGRA_RTC_REG_INTR_STATUS 0x02c

	/* bits in INTR_MASK */
	#define TEGRA_RTC_INTR_MASK_MSEC_CDN_ALARM (1<<4)
	#define TEGRA_RTC_INTR_MASK_SEC_CDN_ALARM (1<<3)
	#define TEGRA_RTC_INTR_MASK_MSEC_ALARM (1<<2)
	#define TEGRA_RTC_INTR_MASK_SEC_ALARM1 (1<<1)
	#define TEGRA_RTC_INTR_MASK_SEC_ALARM0 (1<<0)

	/* bits in INTR_STATUS */
	#define TEGRA_RTC_INTR_STATUS_MSEC_CDN_ALARM (1<<4)
	#define TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM (1<<3)
	#define TEGRA_RTC_INTR_STATUS_MSEC_ALARM (1<<2)
	#define TEGRA_RTC_INTR_STATUS_SEC_ALARM1 (1<<1)
	#define TEGRA_RTC_INTR_STATUS_SEC_ALARM0 (1<<0)

	struct tegra_rtc_info {
	struct platform_device *pdev;
	struct rtc_device *rtc_dev;
	void __iomem rtc_base; / NULL if not initialized. */
	struct clk *clk;
	int tegra_rtc_irq; /* alarm and periodic irq */
	spinlock_t tegra_rtc_lock;
	};

	/* RTC hardware is busy when it is updating its values over AHB once
	* every eight 32kHz clocks (~250uS).
	* outside of these updates the CPU is free to write.
	* CPU is always free to read.
	*/
	static inline u32 tegra_rtc_check_busy(struct tegra_rtc_info *info)
	{
	return readl(info->rtc_base + TEGRA_RTC_REG_BUSY) & 1;
	}

	/* Wait for hardware to be ready for writing.
	* This function tries to maximize the amount of time before the next update.
	* It does this by waiting for the RTC to become busy with its periodic update,
	* then returning once the RTC first becomes not busy.
	* This periodic update (where the seconds and milliseconds are copied to the
	* AHB side) occurs every eight 32kHz clocks (~250uS).
	* The behavior of this function allows us to make some assumptions without
	* introducing a race, because 250uS is plenty of time to read/write a value.
	*/
	static int tegra_rtc_wait_while_busy(struct device *dev)
	{
	struct tegra_rtc_info *info = dev_get_drvdata(dev);

	int retries = 500; /* ~490 us is the worst case, ~250 us is best. */

	/* first wait for the RTC to become busy. this is when it
	* posts its updated seconds+msec registers to AHB side. */
	while (tegra_rtc_check_busy(info)) {
	if (!retries--)
	goto retry_failed;
	udelay(1);
	}

	/* now we have about 250 us to manipulate registers */
	return 0;

	retry_failed:
	dev_err(dev, "write failed:retry count exceeded.\n");
	return -ETIMEDOUT;
	}

	static int tegra_rtc_read_time(struct device dev, struct rtc_time tm)
	{
	struct tegra_rtc_info *info = dev_get_drvdata(dev);
	unsigned long sec, msec;
	unsigned long sl_irq_flags;

	/* RTC hardware copies seconds to shadow seconds when a read
	* of milliseconds occurs. use a lock to keep other threads out. */
	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);

	msec = readl(info->rtc_base + TEGRA_RTC_REG_MILLI_SECONDS);
	sec = readl(info->rtc_base + TEGRA_RTC_REG_SHADOW_SECONDS);

	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);

	rtc_time_to_tm(sec, tm);

	dev_vdbg(dev, "time read as %lu. %d/%d/%d %d:%02u:%02u\n",
	sec,
	tm->tm_mon + 1,
	tm->tm_mday,
	tm->tm_year + 1900,
	tm->tm_hour,
	tm->tm_min,
	tm->tm_sec
	);

	return 0;
	}

	static int tegra_rtc_set_time(struct device dev, struct rtc_time tm)
	{
	struct tegra_rtc_info *info = dev_get_drvdata(dev);
	unsigned long sec;
	int ret;

	/* convert tm to seconds. */
	rtc_tm_to_time(tm, &sec);

	dev_vdbg(dev, "time set to %lu. %d/%d/%d %d:%02u:%02u\n",
	sec,
	tm->tm_mon+1,
	tm->tm_mday,
	tm->tm_year+1900,
	tm->tm_hour,
	tm->tm_min,
	tm->tm_sec
	);

	/* seconds only written if wait succeeded. */
	ret = tegra_rtc_wait_while_busy(dev);
	if (!ret)
	writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS);

	dev_vdbg(dev, "time read back as %d\n",
	readl(info->rtc_base + TEGRA_RTC_REG_SECONDS));

	return ret;
	}

	static int tegra_rtc_read_alarm(struct device dev, struct rtc_wkalrm alarm)
	{
	struct tegra_rtc_info *info = dev_get_drvdata(dev);
	unsigned long sec;
	unsigned tmp;

	sec = readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);

	if (sec == 0) {
	/* alarm is disabled. */
	alarm->enabled = 0;
	} else {
	/* alarm is enabled. */
	alarm->enabled = 1;
	rtc_time_to_tm(sec, &alarm->time);
	}

	tmp = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
	alarm->pending = (tmp & TEGRA_RTC_INTR_STATUS_SEC_ALARM0) != 0;

	return 0;
	}

	static int tegra_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
	{
	struct tegra_rtc_info *info = dev_get_drvdata(dev);
	unsigned status;
	unsigned long sl_irq_flags;

	tegra_rtc_wait_while_busy(dev);
	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);

	/* read the original value, and OR in the flag. */
	status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
	if (enabled)
	status \|= TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* set it */
	else
	status &= ~TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* clear it */

	writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);

	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);

	return 0;
	}

	static int tegra_rtc_set_alarm(struct device dev, struct rtc_wkalrm alarm)
	{
	struct tegra_rtc_info *info = dev_get_drvdata(dev);
	unsigned long sec;

	if (alarm->enabled)
	rtc_tm_to_time(&alarm->time, &sec);
	else
	sec = 0;

	tegra_rtc_wait_while_busy(dev);
	writel(sec, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
	dev_vdbg(dev, "alarm read back as %d\n",
	readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));

	/* if successfully written and alarm is enabled ... */
	if (sec) {
	tegra_rtc_alarm_irq_enable(dev, 1);

	dev_vdbg(dev, "alarm set as %lu. %d/%d/%d %d:%02u:%02u\n",
	sec,
	alarm->time.tm_mon+1,
	alarm->time.tm_mday,
	alarm->time.tm_year+1900,
	alarm->time.tm_hour,
	alarm->time.tm_min,
	alarm->time.tm_sec);
	} else {
	/* disable alarm if 0 or write error. */
	dev_vdbg(dev, "alarm disabled\n");
	tegra_rtc_alarm_irq_enable(dev, 0);
	}

	return 0;
	}

	static int tegra_rtc_proc(struct device dev, struct seq_file seq)
	{
	if (!dev \|\| !dev->driver)
	return 0;

	seq_printf(seq, "name\t\t: %s\n", dev_name(dev));

	return 0;
	}

	static irqreturn_t tegra_rtc_irq_handler(int irq, void *data)
	{
	struct device *dev = data;
	struct tegra_rtc_info *info = dev_get_drvdata(dev);
	unsigned long events = 0;
	unsigned status;
	unsigned long sl_irq_flags;

	status = readl(info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
	if (status) {
	/* clear the interrupt masks and status on any irq. */
	tegra_rtc_wait_while_busy(dev);
	spin_lock_irqsave(&info->tegra_rtc_lock, sl_irq_flags);
	writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);
	writel(status, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
	spin_unlock_irqrestore(&info->tegra_rtc_lock, sl_irq_flags);
	}

	/* check if Alarm */
	if ((status & TEGRA_RTC_INTR_STATUS_SEC_ALARM0))
	events \|= RTC_IRQF \| RTC_AF;

	/* check if Periodic */
	if ((status & TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM))
	events \|= RTC_IRQF \| RTC_PF;

	rtc_update_irq(info->rtc_dev, 1, events);

	return IRQ_HANDLED;
	}

	static const struct rtc_class_ops tegra_rtc_ops = {
	.read_time = tegra_rtc_read_time,
	.set_time = tegra_rtc_set_time,
	.read_alarm = tegra_rtc_read_alarm,
	.set_alarm = tegra_rtc_set_alarm,
	.proc = tegra_rtc_proc,
	.alarm_irq_enable = tegra_rtc_alarm_irq_enable,
	};

	static const struct of_device_id tegra_rtc_dt_match[] = {
	{ .compatible = "nvidia,tegra20-rtc", },
	{}
	};
	MODULE_DEVICE_TABLE(of, tegra_rtc_dt_match);

	static int __init tegra_rtc_probe(struct platform_device *pdev)
	{
	struct tegra_rtc_info *info;
	struct resource *res;
	int ret;

	info = devm_kzalloc(&pdev->dev, sizeof(struct tegra_rtc_info),
	GFP_KERNEL);
	if (!info)
	return -ENOMEM;

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

	ret = platform_get_irq(pdev, 0);
	if (ret <= 0) {
	dev_err(&pdev->dev, "failed to get platform IRQ: %d\n", ret);
	return ret;
	}

	info->tegra_rtc_irq = ret;

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

	ret = clk_prepare_enable(info->clk);
	if (ret < 0)
	return ret;

	/* set context info. */
	info->pdev = pdev;
	spin_lock_init(&info->tegra_rtc_lock);

	platform_set_drvdata(pdev, info);

	/* clear out the hardware. */
	writel(0, info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0);
	writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
	writel(0, info->rtc_base + TEGRA_RTC_REG_INTR_MASK);

	device_init_wakeup(&pdev->dev, 1);

	info->rtc_dev = devm_rtc_device_register(&pdev->dev,
	dev_name(&pdev->dev), &tegra_rtc_ops,
	THIS_MODULE);
	if (IS_ERR(info->rtc_dev)) {
	ret = PTR_ERR(info->rtc_dev);
	dev_err(&pdev->dev, "Unable to register device (err=%d).\n",
	ret);
	goto disable_clk;
	}

	ret = devm_request_irq(&pdev->dev, info->tegra_rtc_irq,
	tegra_rtc_irq_handler, IRQF_TRIGGER_HIGH,
	dev_name(&pdev->dev), &pdev->dev);
	if (ret) {
	dev_err(&pdev->dev,
	"Unable to request interrupt for device (err=%d).\n",
	ret);
	goto disable_clk;
	}

	dev_notice(&pdev->dev, "Tegra internal Real Time Clock\n");

	return 0;

	disable_clk:
	clk_disable_unprepare(info->clk);
	return ret;
	}

	static int tegra_rtc_remove(struct platform_device *pdev)
	{
	struct tegra_rtc_info *info = platform_get_drvdata(pdev);

	clk_disable_unprepare(info->clk);

	return 0;
	}

	#ifdef CONFIG_PM_SLEEP
	static int tegra_rtc_suspend(struct device *dev)
	{
	struct tegra_rtc_info *info = dev_get_drvdata(dev);

	tegra_rtc_wait_while_busy(dev);

	/* only use ALARM0 as a wake source. */
	writel(0xffffffff, info->rtc_base + TEGRA_RTC_REG_INTR_STATUS);
	writel(TEGRA_RTC_INTR_STATUS_SEC_ALARM0,
	info->rtc_base + TEGRA_RTC_REG_INTR_MASK);

	dev_vdbg(dev, "alarm sec = %d\n",
	readl(info->rtc_base + TEGRA_RTC_REG_SECONDS_ALARM0));

	dev_vdbg(dev, "Suspend (device_may_wakeup=%d) irq:%d\n",
	device_may_wakeup(dev), info->tegra_rtc_irq);

	/* leave the alarms on as a wake source. */
	if (device_may_wakeup(dev))
	enable_irq_wake(info->tegra_rtc_irq);

	return 0;
	}

	static int tegra_rtc_resume(struct device *dev)
	{
	struct tegra_rtc_info *info = dev_get_drvdata(dev);

	dev_vdbg(dev, "Resume (device_may_wakeup=%d)\n",
	device_may_wakeup(dev));
	/* alarms were left on as a wake source, turn them off. */
	if (device_may_wakeup(dev))
	disable_irq_wake(info->tegra_rtc_irq);

	return 0;
	}
	#endif

	static SIMPLE_DEV_PM_OPS(tegra_rtc_pm_ops, tegra_rtc_suspend, tegra_rtc_resume);

	static void tegra_rtc_shutdown(struct platform_device *pdev)
	{
	dev_vdbg(&pdev->dev, "disabling interrupts.\n");
	tegra_rtc_alarm_irq_enable(&pdev->dev, 0);
	}

	MODULE_ALIAS("platform:tegra_rtc");
	static struct platform_driver tegra_rtc_driver = {
	.remove = tegra_rtc_remove,
	.shutdown = tegra_rtc_shutdown,
	.driver = {
	.name = "tegra_rtc",
	.of_match_table = tegra_rtc_dt_match,
	.pm = &tegra_rtc_pm_ops,
	},
	};

	module_platform_driver_probe(tegra_rtc_driver, tegra_rtc_probe);

	MODULE_AUTHOR("Jon Mayo <jmayo@nvidia.com>");
	MODULE_DESCRIPTION("driver for Tegra internal RTC");
	MODULE_LICENSE("GPL");