drivers/rtc/rtc-wm831x.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  *	Real Time Clock driver for Wolfson Microelectronics WM831x
  *
  *	Copyright (C) 2009 Wolfson Microelectronics PLC.
  *
  *  Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
  *
  */

 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/time.h>
 #include <linux/rtc.h>
 #include <linux/slab.h>
 #include <linux/bcd.h>
 #include <linux/interrupt.h>
 #include <linux/ioctl.h>
 #include <linux/completion.h>
 #include <linux/mfd/wm831x/core.h>
 #include <linux/delay.h>
 #include <linux/platform_device.h>
 #include <linux/random.h>

 /*
  * R16416 (0x4020) - RTC Write Counter
  */
 #define WM831X_RTC_WR_CNT_MASK                  0xFFFF  /* RTC_WR_CNT - [15:0] */
 #define WM831X_RTC_WR_CNT_SHIFT                      0  /* RTC_WR_CNT - [15:0] */
 #define WM831X_RTC_WR_CNT_WIDTH                     16  /* RTC_WR_CNT - [15:0] */

 /*
  * R16417 (0x4021) - RTC Time 1
  */
 #define WM831X_RTC_TIME_MASK                    0xFFFF  /* RTC_TIME - [15:0] */
 #define WM831X_RTC_TIME_SHIFT                        0  /* RTC_TIME - [15:0] */
 #define WM831X_RTC_TIME_WIDTH                       16  /* RTC_TIME - [15:0] */

 /*
  * R16418 (0x4022) - RTC Time 2
  */
 #define WM831X_RTC_TIME_MASK                    0xFFFF  /* RTC_TIME - [15:0] */
 #define WM831X_RTC_TIME_SHIFT                        0  /* RTC_TIME - [15:0] */
 #define WM831X_RTC_TIME_WIDTH                       16  /* RTC_TIME - [15:0] */

 /*
  * R16419 (0x4023) - RTC Alarm 1
  */
 #define WM831X_RTC_ALM_MASK                     0xFFFF  /* RTC_ALM - [15:0] */
 #define WM831X_RTC_ALM_SHIFT                         0  /* RTC_ALM - [15:0] */
 #define WM831X_RTC_ALM_WIDTH                        16  /* RTC_ALM - [15:0] */

 /*
  * R16420 (0x4024) - RTC Alarm 2
  */
 #define WM831X_RTC_ALM_MASK                     0xFFFF  /* RTC_ALM - [15:0] */
 #define WM831X_RTC_ALM_SHIFT                         0  /* RTC_ALM - [15:0] */
 #define WM831X_RTC_ALM_WIDTH                        16  /* RTC_ALM - [15:0] */

 /*
  * R16421 (0x4025) - RTC Control
  */
 #define WM831X_RTC_VALID                        0x8000  /* RTC_VALID */
 #define WM831X_RTC_VALID_MASK                   0x8000  /* RTC_VALID */
 #define WM831X_RTC_VALID_SHIFT                      15  /* RTC_VALID */
 #define WM831X_RTC_VALID_WIDTH                       1  /* RTC_VALID */
 #define WM831X_RTC_SYNC_BUSY                    0x4000  /* RTC_SYNC_BUSY */
 #define WM831X_RTC_SYNC_BUSY_MASK               0x4000  /* RTC_SYNC_BUSY */
 #define WM831X_RTC_SYNC_BUSY_SHIFT                  14  /* RTC_SYNC_BUSY */
 #define WM831X_RTC_SYNC_BUSY_WIDTH                   1  /* RTC_SYNC_BUSY */
 #define WM831X_RTC_ALM_ENA                      0x0400  /* RTC_ALM_ENA */
 #define WM831X_RTC_ALM_ENA_MASK                 0x0400  /* RTC_ALM_ENA */
 #define WM831X_RTC_ALM_ENA_SHIFT                    10  /* RTC_ALM_ENA */
 #define WM831X_RTC_ALM_ENA_WIDTH                     1  /* RTC_ALM_ENA */
 #define WM831X_RTC_PINT_FREQ_MASK               0x0070  /* RTC_PINT_FREQ - [6:4] */
 #define WM831X_RTC_PINT_FREQ_SHIFT                   4  /* RTC_PINT_FREQ - [6:4] */
 #define WM831X_RTC_PINT_FREQ_WIDTH                   3  /* RTC_PINT_FREQ - [6:4] */

 /*
  * R16422 (0x4026) - RTC Trim
  */
 #define WM831X_RTC_TRIM_MASK                    0x03FF  /* RTC_TRIM - [9:0] */
 #define WM831X_RTC_TRIM_SHIFT                        0  /* RTC_TRIM - [9:0] */
 #define WM831X_RTC_TRIM_WIDTH                       10  /* RTC_TRIM - [9:0] */

 #define WM831X_SET_TIME_RETRIES	5
 #define WM831X_GET_TIME_RETRIES	5

 struct wm831x_rtc {
 	struct wm831x *wm831x;
 	struct rtc_device *rtc;
 	unsigned int alarm_enabled:1;
 };

 static void wm831x_rtc_add_randomness(struct wm831x *wm831x)
 {
 	int ret;
 	u16 reg;

 	/*
 	 * The write counter contains a pseudo-random number which is
 	 * regenerated every time we set the RTC so it should be a
 	 * useful per-system source of entropy.
 	 */
 	ret = wm831x_reg_read(wm831x, WM831X_RTC_WRITE_COUNTER);
 	if (ret >= 0) {
 		reg = ret;
 		add_device_randomness(&reg, sizeof(reg));
 	} else {
 		dev_warn(wm831x->dev, "Failed to read RTC write counter: %d\n",
 			 ret);
 	}
 }

 /*
  * Read current time and date in RTC
  */
 static int wm831x_rtc_readtime(struct device *dev, struct rtc_time *tm)
 {
 	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
 	struct wm831x *wm831x = wm831x_rtc->wm831x;
 	u16 time1[2], time2[2];
 	int ret;
 	int count = 0;

 	/* Has the RTC been programmed? */
 	ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
 	if (ret < 0) {
 		dev_err(dev, "Failed to read RTC control: %d\n", ret);
 		return ret;
 	}
 	if (!(ret & WM831X_RTC_VALID)) {
 		dev_dbg(dev, "RTC not yet configured\n");
 		return -EINVAL;
 	}

 	/* Read twice to make sure we don't read a corrupt, partially
 	 * incremented, value.
 	 */
 	do {
 		ret = wm831x_bulk_read(wm831x, WM831X_RTC_TIME_1,
 				       2, time1);
 		if (ret != 0)
 			continue;

 		ret = wm831x_bulk_read(wm831x, WM831X_RTC_TIME_1,
 				       2, time2);
 		if (ret != 0)
 			continue;

 		if (memcmp(time1, time2, sizeof(time1)) == 0) {
 			u32 time = (time1[0] << 16) | time1[1];

 			rtc_time64_to_tm(time, tm);
 			return 0;
 		}

 	} while (++count < WM831X_GET_TIME_RETRIES);

 	dev_err(dev, "Timed out reading current time\n");

 	return -EIO;
 }

 /*
  * Set current time and date in RTC
  */
 static int wm831x_rtc_settime(struct device *dev, struct rtc_time *tm)
 {
 	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
 	struct wm831x *wm831x = wm831x_rtc->wm831x;
 	struct rtc_time new_tm;
 	unsigned long time, new_time;
 	int ret;
 	int count = 0;

 	time = rtc_tm_to_time64(tm);

 	ret = wm831x_reg_write(wm831x, WM831X_RTC_TIME_1,
 			       (time >> 16) & 0xffff);
 	if (ret < 0) {
 		dev_err(dev, "Failed to write TIME_1: %d\n", ret);
 		return ret;
 	}

 	ret = wm831x_reg_write(wm831x, WM831X_RTC_TIME_2, time & 0xffff);
 	if (ret < 0) {
 		dev_err(dev, "Failed to write TIME_2: %d\n", ret);
 		return ret;
 	}

 	/* Wait for the update to complete - should happen first time
 	 * round but be conservative.
 	 */
 	do {
 		msleep(1);

 		ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
 		if (ret < 0)
 			ret = WM831X_RTC_SYNC_BUSY;
 	} while (!(ret & WM831X_RTC_SYNC_BUSY) &&
 		 ++count < WM831X_SET_TIME_RETRIES);

 	if (ret & WM831X_RTC_SYNC_BUSY) {
 		dev_err(dev, "Timed out writing RTC update\n");
 		return -EIO;
 	}

 	/* Check that the update was accepted; security features may
 	 * have caused the update to be ignored.
 	 */
 	ret = wm831x_rtc_readtime(dev, &new_tm);
 	if (ret < 0)
 		return ret;

 	new_time = rtc_tm_to_time64(&new_tm);

 	/* Allow a second of change in case of tick */
 	if (new_time - time > 1) {
 		dev_err(dev, "RTC update not permitted by hardware\n");
 		return -EPERM;
 	}

 	return 0;
 }

 /*
  * Read alarm time and date in RTC
  */
 static int wm831x_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
 	int ret;
 	u16 data[2];
 	u32 time;

 	ret = wm831x_bulk_read(wm831x_rtc->wm831x, WM831X_RTC_ALARM_1,
 			       2, data);
 	if (ret != 0) {
 		dev_err(dev, "Failed to read alarm time: %d\n", ret);
 		return ret;
 	}

 	time = (data[0] << 16) | data[1];

 	rtc_time64_to_tm(time, &alrm->time);

 	ret = wm831x_reg_read(wm831x_rtc->wm831x, WM831X_RTC_CONTROL);
 	if (ret < 0) {
 		dev_err(dev, "Failed to read RTC control: %d\n", ret);
 		return ret;
 	}

 	if (ret & WM831X_RTC_ALM_ENA)
 		alrm->enabled = 1;
 	else
 		alrm->enabled = 0;

 	return 0;
 }

 static int wm831x_rtc_stop_alarm(struct wm831x_rtc *wm831x_rtc)
 {
 	wm831x_rtc->alarm_enabled = 0;

 	return wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
 			       WM831X_RTC_ALM_ENA, 0);
 }

 static int wm831x_rtc_start_alarm(struct wm831x_rtc *wm831x_rtc)
 {
 	wm831x_rtc->alarm_enabled = 1;

 	return wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
 			       WM831X_RTC_ALM_ENA, WM831X_RTC_ALM_ENA);
 }

 static int wm831x_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
 	struct wm831x *wm831x = wm831x_rtc->wm831x;
 	int ret;
 	unsigned long time;

 	time = rtc_tm_to_time64(&alrm->time);

 	ret = wm831x_rtc_stop_alarm(wm831x_rtc);
 	if (ret < 0) {
 		dev_err(dev, "Failed to stop alarm: %d\n", ret);
 		return ret;
 	}

 	ret = wm831x_reg_write(wm831x, WM831X_RTC_ALARM_1,
 			       (time >> 16) & 0xffff);
 	if (ret < 0) {
 		dev_err(dev, "Failed to write ALARM_1: %d\n", ret);
 		return ret;
 	}

 	ret = wm831x_reg_write(wm831x, WM831X_RTC_ALARM_2, time & 0xffff);
 	if (ret < 0) {
 		dev_err(dev, "Failed to write ALARM_2: %d\n", ret);
 		return ret;
 	}

 	if (alrm->enabled) {
 		ret = wm831x_rtc_start_alarm(wm831x_rtc);
 		if (ret < 0) {
 			dev_err(dev, "Failed to start alarm: %d\n", ret);
 			return ret;
 		}
 	}

 	return 0;
 }

 static int wm831x_rtc_alarm_irq_enable(struct device *dev,
 				       unsigned int enabled)
 {
 	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);

 	if (enabled)
 		return wm831x_rtc_start_alarm(wm831x_rtc);
 	else
 		return wm831x_rtc_stop_alarm(wm831x_rtc);
 }

 static irqreturn_t wm831x_alm_irq(int irq, void *data)
 {
 	struct wm831x_rtc *wm831x_rtc = data;

 	rtc_update_irq(wm831x_rtc->rtc, 1, RTC_IRQF | RTC_AF);

 	return IRQ_HANDLED;
 }

 static const struct rtc_class_ops wm831x_rtc_ops = {
 	.read_time = wm831x_rtc_readtime,
 	.set_time = wm831x_rtc_settime,
 	.read_alarm = wm831x_rtc_readalarm,
 	.set_alarm = wm831x_rtc_setalarm,
 	.alarm_irq_enable = wm831x_rtc_alarm_irq_enable,
 };

 #ifdef CONFIG_PM
 /* Turn off the alarm if it should not be a wake source. */
 static int wm831x_rtc_suspend(struct device *dev)
 {
 	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
 	int ret, enable;

 	if (wm831x_rtc->alarm_enabled && device_may_wakeup(dev))
 		enable = WM831X_RTC_ALM_ENA;
 	else
 		enable = 0;

 	ret = wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
 			      WM831X_RTC_ALM_ENA, enable);
 	if (ret != 0)
 		dev_err(dev, "Failed to update RTC alarm: %d\n", ret);

 	return 0;
 }

 /* Enable the alarm if it should be enabled (in case it was disabled to
  * prevent use as a wake source).
  */
 static int wm831x_rtc_resume(struct device *dev)
 {
 	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
 	int ret;

 	if (wm831x_rtc->alarm_enabled) {
 		ret = wm831x_rtc_start_alarm(wm831x_rtc);
 		if (ret != 0)
 			dev_err(dev, "Failed to restart RTC alarm: %d\n", ret);
 	}

 	return 0;
 }

 /* Unconditionally disable the alarm */
 static int wm831x_rtc_freeze(struct device *dev)
 {
 	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
 	int ret;

 	ret = wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
 			      WM831X_RTC_ALM_ENA, 0);
 	if (ret != 0)
 		dev_err(dev, "Failed to stop RTC alarm: %d\n", ret);

 	return 0;
 }
 #else
 #define wm831x_rtc_suspend NULL
 #define wm831x_rtc_resume NULL
 #define wm831x_rtc_freeze NULL
 #endif

 static int wm831x_rtc_probe(struct platform_device *pdev)
 {
 	struct wm831x *wm831x = dev_get_drvdata(pdev->dev.parent);
 	struct wm831x_rtc *wm831x_rtc;
 	int alm_irq = wm831x_irq(wm831x, platform_get_irq_byname(pdev, "ALM"));
 	int ret = 0;

 	wm831x_rtc = devm_kzalloc(&pdev->dev, sizeof(*wm831x_rtc), GFP_KERNEL);
 	if (wm831x_rtc == NULL)
 		return -ENOMEM;

 	platform_set_drvdata(pdev, wm831x_rtc);
 	wm831x_rtc->wm831x = wm831x;

 	ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Failed to read RTC control: %d\n", ret);
 		return ret;
 	}
 	if (ret & WM831X_RTC_ALM_ENA)
 		wm831x_rtc->alarm_enabled = 1;

 	device_init_wakeup(&pdev->dev, 1);

 	wm831x_rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
 	if (IS_ERR(wm831x_rtc->rtc))
 		return PTR_ERR(wm831x_rtc->rtc);

 	wm831x_rtc->rtc->ops = &wm831x_rtc_ops;
 	wm831x_rtc->rtc->range_max = U32_MAX;

 	ret = rtc_register_device(wm831x_rtc->rtc);
 	if (ret)
 		return ret;

 	ret = devm_request_threaded_irq(&pdev->dev, alm_irq, NULL,
 				wm831x_alm_irq,
 				IRQF_TRIGGER_RISING, "RTC alarm",
 				wm831x_rtc);
 	if (ret != 0) {
 		dev_err(&pdev->dev, "Failed to request alarm IRQ %d: %d\n",
 			alm_irq, ret);
 	}

 	wm831x_rtc_add_randomness(wm831x);

 	return 0;
 }

 static const struct dev_pm_ops wm831x_rtc_pm_ops = {
 	.suspend = wm831x_rtc_suspend,
 	.resume = wm831x_rtc_resume,

 	.freeze = wm831x_rtc_freeze,
 	.thaw = wm831x_rtc_resume,
 	.restore = wm831x_rtc_resume,

 	.poweroff = wm831x_rtc_suspend,
 };

 static struct platform_driver wm831x_rtc_driver = {
 	.probe = wm831x_rtc_probe,
 	.driver = {
 		.name = "wm831x-rtc",
 		.pm = &wm831x_rtc_pm_ops,
 	},
 };

 module_platform_driver(wm831x_rtc_driver);

 MODULE_AUTHOR("Mark Brown <broonie@opensource.wolfsonmicro.com>");
 MODULE_DESCRIPTION("RTC driver for the WM831x series PMICs");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:wm831x-rtc");
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Real Time Clock driver for Wolfson Microelectronics WM831x
	*
	* Copyright (C) 2009 Wolfson Microelectronics PLC.
	*
	* Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
	*
	*/

	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/time.h>
	#include <linux/rtc.h>
	#include <linux/slab.h>
	#include <linux/bcd.h>
	#include <linux/interrupt.h>
	#include <linux/ioctl.h>
	#include <linux/completion.h>
	#include <linux/mfd/wm831x/core.h>
	#include <linux/delay.h>
	#include <linux/platform_device.h>
	#include <linux/random.h>

	/*
	* R16416 (0x4020) - RTC Write Counter
	*/
	#define WM831X_RTC_WR_CNT_MASK 0xFFFF /* RTC_WR_CNT - [15:0] */
	#define WM831X_RTC_WR_CNT_SHIFT 0 /* RTC_WR_CNT - [15:0] */
	#define WM831X_RTC_WR_CNT_WIDTH 16 /* RTC_WR_CNT - [15:0] */

	/*
	* R16417 (0x4021) - RTC Time 1
	*/
	#define WM831X_RTC_TIME_MASK 0xFFFF /* RTC_TIME - [15:0] */
	#define WM831X_RTC_TIME_SHIFT 0 /* RTC_TIME - [15:0] */
	#define WM831X_RTC_TIME_WIDTH 16 /* RTC_TIME - [15:0] */

	/*
	* R16418 (0x4022) - RTC Time 2
	*/
	#define WM831X_RTC_TIME_MASK 0xFFFF /* RTC_TIME - [15:0] */
	#define WM831X_RTC_TIME_SHIFT 0 /* RTC_TIME - [15:0] */
	#define WM831X_RTC_TIME_WIDTH 16 /* RTC_TIME - [15:0] */

	/*
	* R16419 (0x4023) - RTC Alarm 1
	*/
	#define WM831X_RTC_ALM_MASK 0xFFFF /* RTC_ALM - [15:0] */
	#define WM831X_RTC_ALM_SHIFT 0 /* RTC_ALM - [15:0] */
	#define WM831X_RTC_ALM_WIDTH 16 /* RTC_ALM - [15:0] */

	/*
	* R16420 (0x4024) - RTC Alarm 2
	*/
	#define WM831X_RTC_ALM_MASK 0xFFFF /* RTC_ALM - [15:0] */
	#define WM831X_RTC_ALM_SHIFT 0 /* RTC_ALM - [15:0] */
	#define WM831X_RTC_ALM_WIDTH 16 /* RTC_ALM - [15:0] */

	/*
	* R16421 (0x4025) - RTC Control
	*/
	#define WM831X_RTC_VALID 0x8000 /* RTC_VALID */
	#define WM831X_RTC_VALID_MASK 0x8000 /* RTC_VALID */
	#define WM831X_RTC_VALID_SHIFT 15 /* RTC_VALID */
	#define WM831X_RTC_VALID_WIDTH 1 /* RTC_VALID */
	#define WM831X_RTC_SYNC_BUSY 0x4000 /* RTC_SYNC_BUSY */
	#define WM831X_RTC_SYNC_BUSY_MASK 0x4000 /* RTC_SYNC_BUSY */
	#define WM831X_RTC_SYNC_BUSY_SHIFT 14 /* RTC_SYNC_BUSY */
	#define WM831X_RTC_SYNC_BUSY_WIDTH 1 /* RTC_SYNC_BUSY */
	#define WM831X_RTC_ALM_ENA 0x0400 /* RTC_ALM_ENA */
	#define WM831X_RTC_ALM_ENA_MASK 0x0400 /* RTC_ALM_ENA */
	#define WM831X_RTC_ALM_ENA_SHIFT 10 /* RTC_ALM_ENA */
	#define WM831X_RTC_ALM_ENA_WIDTH 1 /* RTC_ALM_ENA */
	#define WM831X_RTC_PINT_FREQ_MASK 0x0070 /* RTC_PINT_FREQ - [6:4] */
	#define WM831X_RTC_PINT_FREQ_SHIFT 4 /* RTC_PINT_FREQ - [6:4] */
	#define WM831X_RTC_PINT_FREQ_WIDTH 3 /* RTC_PINT_FREQ - [6:4] */

	/*
	* R16422 (0x4026) - RTC Trim
	*/
	#define WM831X_RTC_TRIM_MASK 0x03FF /* RTC_TRIM - [9:0] */
	#define WM831X_RTC_TRIM_SHIFT 0 /* RTC_TRIM - [9:0] */
	#define WM831X_RTC_TRIM_WIDTH 10 /* RTC_TRIM - [9:0] */

	#define WM831X_SET_TIME_RETRIES 5
	#define WM831X_GET_TIME_RETRIES 5

	struct wm831x_rtc {
	struct wm831x *wm831x;
	struct rtc_device *rtc;
	unsigned int alarm_enabled:1;
	};

	static void wm831x_rtc_add_randomness(struct wm831x *wm831x)
	{
	int ret;
	u16 reg;

	/*
	* The write counter contains a pseudo-random number which is
	* regenerated every time we set the RTC so it should be a
	* useful per-system source of entropy.
	*/
	ret = wm831x_reg_read(wm831x, WM831X_RTC_WRITE_COUNTER);
	if (ret >= 0) {
	reg = ret;
	add_device_randomness(&reg, sizeof(reg));
	} else {
	dev_warn(wm831x->dev, "Failed to read RTC write counter: %d\n",
	ret);
	}
	}

	/*
	* Read current time and date in RTC
	*/
	static int wm831x_rtc_readtime(struct device dev, struct rtc_time tm)
	{
	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
	struct wm831x *wm831x = wm831x_rtc->wm831x;
	u16 time1[2], time2[2];
	int ret;
	int count = 0;

	/* Has the RTC been programmed? */
	ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
	if (ret < 0) {
	dev_err(dev, "Failed to read RTC control: %d\n", ret);
	return ret;
	}
	if (!(ret & WM831X_RTC_VALID)) {
	dev_dbg(dev, "RTC not yet configured\n");
	return -EINVAL;
	}

	/* Read twice to make sure we don't read a corrupt, partially
	* incremented, value.
	*/
	do {
	ret = wm831x_bulk_read(wm831x, WM831X_RTC_TIME_1,
	2, time1);
	if (ret != 0)
	continue;

	ret = wm831x_bulk_read(wm831x, WM831X_RTC_TIME_1,
	2, time2);
	if (ret != 0)
	continue;

	if (memcmp(time1, time2, sizeof(time1)) == 0) {
	u32 time = (time1[0] << 16) \| time1[1];

	rtc_time64_to_tm(time, tm);
	return 0;
	}

	} while (++count < WM831X_GET_TIME_RETRIES);

	dev_err(dev, "Timed out reading current time\n");

	return -EIO;
	}

	/*
	* Set current time and date in RTC
	*/
	static int wm831x_rtc_settime(struct device dev, struct rtc_time tm)
	{
	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
	struct wm831x *wm831x = wm831x_rtc->wm831x;
	struct rtc_time new_tm;
	unsigned long time, new_time;
	int ret;
	int count = 0;

	time = rtc_tm_to_time64(tm);

	ret = wm831x_reg_write(wm831x, WM831X_RTC_TIME_1,
	(time >> 16) & 0xffff);
	if (ret < 0) {
	dev_err(dev, "Failed to write TIME_1: %d\n", ret);
	return ret;
	}

	ret = wm831x_reg_write(wm831x, WM831X_RTC_TIME_2, time & 0xffff);
	if (ret < 0) {
	dev_err(dev, "Failed to write TIME_2: %d\n", ret);
	return ret;
	}

	/* Wait for the update to complete - should happen first time
	* round but be conservative.
	*/
	do {
	msleep(1);

	ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
	if (ret < 0)
	ret = WM831X_RTC_SYNC_BUSY;
	} while (!(ret & WM831X_RTC_SYNC_BUSY) &&
	++count < WM831X_SET_TIME_RETRIES);

	if (ret & WM831X_RTC_SYNC_BUSY) {
	dev_err(dev, "Timed out writing RTC update\n");
	return -EIO;
	}

	/* Check that the update was accepted; security features may
	* have caused the update to be ignored.
	*/
	ret = wm831x_rtc_readtime(dev, &new_tm);
	if (ret < 0)
	return ret;

	new_time = rtc_tm_to_time64(&new_tm);

	/* Allow a second of change in case of tick */
	if (new_time - time > 1) {
	dev_err(dev, "RTC update not permitted by hardware\n");
	return -EPERM;
	}

	return 0;
	}

	/*
	* Read alarm time and date in RTC
	*/
	static int wm831x_rtc_readalarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
	int ret;
	u16 data[2];
	u32 time;

	ret = wm831x_bulk_read(wm831x_rtc->wm831x, WM831X_RTC_ALARM_1,
	2, data);
	if (ret != 0) {
	dev_err(dev, "Failed to read alarm time: %d\n", ret);
	return ret;
	}

	time = (data[0] << 16) \| data[1];

	rtc_time64_to_tm(time, &alrm->time);

	ret = wm831x_reg_read(wm831x_rtc->wm831x, WM831X_RTC_CONTROL);
	if (ret < 0) {
	dev_err(dev, "Failed to read RTC control: %d\n", ret);
	return ret;
	}

	if (ret & WM831X_RTC_ALM_ENA)
	alrm->enabled = 1;
	else
	alrm->enabled = 0;

	return 0;
	}

	static int wm831x_rtc_stop_alarm(struct wm831x_rtc *wm831x_rtc)
	{
	wm831x_rtc->alarm_enabled = 0;

	return wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
	WM831X_RTC_ALM_ENA, 0);
	}

	static int wm831x_rtc_start_alarm(struct wm831x_rtc *wm831x_rtc)
	{
	wm831x_rtc->alarm_enabled = 1;

	return wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
	WM831X_RTC_ALM_ENA, WM831X_RTC_ALM_ENA);
	}

	static int wm831x_rtc_setalarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
	struct wm831x *wm831x = wm831x_rtc->wm831x;
	int ret;
	unsigned long time;

	time = rtc_tm_to_time64(&alrm->time);

	ret = wm831x_rtc_stop_alarm(wm831x_rtc);
	if (ret < 0) {
	dev_err(dev, "Failed to stop alarm: %d\n", ret);
	return ret;
	}

	ret = wm831x_reg_write(wm831x, WM831X_RTC_ALARM_1,
	(time >> 16) & 0xffff);
	if (ret < 0) {
	dev_err(dev, "Failed to write ALARM_1: %d\n", ret);
	return ret;
	}

	ret = wm831x_reg_write(wm831x, WM831X_RTC_ALARM_2, time & 0xffff);
	if (ret < 0) {
	dev_err(dev, "Failed to write ALARM_2: %d\n", ret);
	return ret;
	}

	if (alrm->enabled) {
	ret = wm831x_rtc_start_alarm(wm831x_rtc);
	if (ret < 0) {
	dev_err(dev, "Failed to start alarm: %d\n", ret);
	return ret;
	}
	}

	return 0;
	}

	static int wm831x_rtc_alarm_irq_enable(struct device *dev,
	unsigned int enabled)
	{
	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);

	if (enabled)
	return wm831x_rtc_start_alarm(wm831x_rtc);
	else
	return wm831x_rtc_stop_alarm(wm831x_rtc);
	}

	static irqreturn_t wm831x_alm_irq(int irq, void *data)
	{
	struct wm831x_rtc *wm831x_rtc = data;

	rtc_update_irq(wm831x_rtc->rtc, 1, RTC_IRQF \| RTC_AF);

	return IRQ_HANDLED;
	}

	static const struct rtc_class_ops wm831x_rtc_ops = {
	.read_time = wm831x_rtc_readtime,
	.set_time = wm831x_rtc_settime,
	.read_alarm = wm831x_rtc_readalarm,
	.set_alarm = wm831x_rtc_setalarm,
	.alarm_irq_enable = wm831x_rtc_alarm_irq_enable,
	};

	#ifdef CONFIG_PM
	/* Turn off the alarm if it should not be a wake source. */
	static int wm831x_rtc_suspend(struct device *dev)
	{
	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
	int ret, enable;

	if (wm831x_rtc->alarm_enabled && device_may_wakeup(dev))
	enable = WM831X_RTC_ALM_ENA;
	else
	enable = 0;

	ret = wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
	WM831X_RTC_ALM_ENA, enable);
	if (ret != 0)
	dev_err(dev, "Failed to update RTC alarm: %d\n", ret);

	return 0;
	}

	/* Enable the alarm if it should be enabled (in case it was disabled to
	* prevent use as a wake source).
	*/
	static int wm831x_rtc_resume(struct device *dev)
	{
	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
	int ret;

	if (wm831x_rtc->alarm_enabled) {
	ret = wm831x_rtc_start_alarm(wm831x_rtc);
	if (ret != 0)
	dev_err(dev, "Failed to restart RTC alarm: %d\n", ret);
	}

	return 0;
	}

	/* Unconditionally disable the alarm */
	static int wm831x_rtc_freeze(struct device *dev)
	{
	struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
	int ret;

	ret = wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
	WM831X_RTC_ALM_ENA, 0);
	if (ret != 0)
	dev_err(dev, "Failed to stop RTC alarm: %d\n", ret);

	return 0;
	}
	#else
	#define wm831x_rtc_suspend NULL
	#define wm831x_rtc_resume NULL
	#define wm831x_rtc_freeze NULL
	#endif

	static int wm831x_rtc_probe(struct platform_device *pdev)
	{
	struct wm831x *wm831x = dev_get_drvdata(pdev->dev.parent);
	struct wm831x_rtc *wm831x_rtc;
	int alm_irq = wm831x_irq(wm831x, platform_get_irq_byname(pdev, "ALM"));
	int ret = 0;

	wm831x_rtc = devm_kzalloc(&pdev->dev, sizeof(*wm831x_rtc), GFP_KERNEL);
	if (wm831x_rtc == NULL)
	return -ENOMEM;

	platform_set_drvdata(pdev, wm831x_rtc);
	wm831x_rtc->wm831x = wm831x;

	ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
	if (ret < 0) {
	dev_err(&pdev->dev, "Failed to read RTC control: %d\n", ret);
	return ret;
	}
	if (ret & WM831X_RTC_ALM_ENA)
	wm831x_rtc->alarm_enabled = 1;

	device_init_wakeup(&pdev->dev, 1);

	wm831x_rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
	if (IS_ERR(wm831x_rtc->rtc))
	return PTR_ERR(wm831x_rtc->rtc);

	wm831x_rtc->rtc->ops = &wm831x_rtc_ops;
	wm831x_rtc->rtc->range_max = U32_MAX;

	ret = rtc_register_device(wm831x_rtc->rtc);
	if (ret)
	return ret;

	ret = devm_request_threaded_irq(&pdev->dev, alm_irq, NULL,
	wm831x_alm_irq,
	IRQF_TRIGGER_RISING, "RTC alarm",
	wm831x_rtc);
	if (ret != 0) {
	dev_err(&pdev->dev, "Failed to request alarm IRQ %d: %d\n",
	alm_irq, ret);
	}

	wm831x_rtc_add_randomness(wm831x);

	return 0;
	}

	static const struct dev_pm_ops wm831x_rtc_pm_ops = {
	.suspend = wm831x_rtc_suspend,
	.resume = wm831x_rtc_resume,

	.freeze = wm831x_rtc_freeze,
	.thaw = wm831x_rtc_resume,
	.restore = wm831x_rtc_resume,

	.poweroff = wm831x_rtc_suspend,
	};

	static struct platform_driver wm831x_rtc_driver = {
	.probe = wm831x_rtc_probe,
	.driver = {
	.name = "wm831x-rtc",
	.pm = &wm831x_rtc_pm_ops,
	},
	};

	module_platform_driver(wm831x_rtc_driver);

	MODULE_AUTHOR("Mark Brown <broonie@opensource.wolfsonmicro.com>");
	MODULE_DESCRIPTION("RTC driver for the WM831x series PMICs");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("platform:wm831x-rtc");