drivers/rtc/rtc-tps6594.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * RTC driver for tps6594 PMIC
  *
  * Copyright (C) 2023 BayLibre Incorporated - https://www.baylibre.com/
  */

 #include <linux/bcd.h>
 #include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/limits.h>
 #include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/mod_devicetable.h>
 #include <linux/property.h>
 #include <linux/rtc.h>
 #include <linux/types.h>
 #include <linux/units.h>

 #include <linux/mfd/tps6594.h>

 // Total number of RTC registers needed to set time
 #define NUM_TIME_REGS (TPS6594_REG_RTC_WEEKS - TPS6594_REG_RTC_SECONDS + 1)

 // Total number of RTC alarm registers
 #define NUM_TIME_ALARM_REGS (NUM_TIME_REGS - 1)

 /*
  * Min and max values supported by 'offset' interface (swapped sign).
  * After conversion, the values do not exceed the range [-32767, 33767]
  * which COMP_REG must conform to.
  */
 #define MIN_OFFSET (-277774)
 #define MAX_OFFSET (277774)

 // Number of ticks per hour
 #define TICKS_PER_HOUR (32768 * 3600)

 // Multiplier for ppb conversions
 #define PPB_MULT NANO

 static int tps6594_rtc_alarm_irq_enable(struct device *dev,
 					unsigned int enabled)
 {
 	struct tps6594 *tps = dev_get_drvdata(dev->parent);
 	u8 val;

 	val = enabled ? TPS6594_BIT_IT_ALARM : 0;

 	return regmap_update_bits(tps->regmap, TPS6594_REG_RTC_INTERRUPTS,
 				  TPS6594_BIT_IT_ALARM, val);
 }

 /* Pulse GET_TIME field of RTC_CTRL_1 to store a timestamp in shadow registers. */
 static int tps6594_rtc_shadow_timestamp(struct device *dev, struct tps6594 *tps)
 {
 	int ret;

 	/*
 	 * Set GET_TIME to 0. Next time we set GET_TIME to 1 we will be sure to store
 	 * an up-to-date timestamp.
 	 */
 	ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
 				TPS6594_BIT_GET_TIME);
 	if (ret < 0)
 		return ret;

 	/*
 	 * Copy content of RTC registers to shadow registers or latches to read
 	 * a coherent timestamp.
 	 */
 	return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
 			       TPS6594_BIT_GET_TIME);
 }

 static int tps6594_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	unsigned char rtc_data[NUM_TIME_REGS];
 	struct tps6594 *tps = dev_get_drvdata(dev->parent);
 	int ret;

 	// Check if RTC is running.
 	ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
 			       TPS6594_BIT_RUN);
 	if (ret < 0)
 		return ret;
 	if (ret == 0)
 		return -EINVAL;

 	ret = tps6594_rtc_shadow_timestamp(dev, tps);
 	if (ret < 0)
 		return ret;

 	// Read shadowed RTC registers.
 	ret = regmap_bulk_read(tps->regmap, TPS6594_REG_RTC_SECONDS, rtc_data,
 			       NUM_TIME_REGS);
 	if (ret < 0)
 		return ret;

 	tm->tm_sec = bcd2bin(rtc_data[0]);
 	tm->tm_min = bcd2bin(rtc_data[1]);
 	tm->tm_hour = bcd2bin(rtc_data[2]);
 	tm->tm_mday = bcd2bin(rtc_data[3]);
 	tm->tm_mon = bcd2bin(rtc_data[4]) - 1;
 	tm->tm_year = bcd2bin(rtc_data[5]) + 100;
 	tm->tm_wday = bcd2bin(rtc_data[6]);

 	return 0;
 }

 static int tps6594_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	unsigned char rtc_data[NUM_TIME_REGS];
 	struct tps6594 *tps = dev_get_drvdata(dev->parent);
 	int ret;

 	rtc_data[0] = bin2bcd(tm->tm_sec);
 	rtc_data[1] = bin2bcd(tm->tm_min);
 	rtc_data[2] = bin2bcd(tm->tm_hour);
 	rtc_data[3] = bin2bcd(tm->tm_mday);
 	rtc_data[4] = bin2bcd(tm->tm_mon + 1);
 	rtc_data[5] = bin2bcd(tm->tm_year - 100);
 	rtc_data[6] = bin2bcd(tm->tm_wday);

 	// Stop RTC while updating the RTC time registers.
 	ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
 				TPS6594_BIT_STOP_RTC);
 	if (ret < 0)
 		return ret;

 	// Update all the time registers in one shot.
 	ret = regmap_bulk_write(tps->regmap, TPS6594_REG_RTC_SECONDS, rtc_data,
 				NUM_TIME_REGS);
 	if (ret < 0)
 		return ret;

 	// Start back RTC.
 	return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
 			       TPS6594_BIT_STOP_RTC);
 }

 static int tps6594_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
 {
 	unsigned char alarm_data[NUM_TIME_ALARM_REGS];
 	u32 int_val;
 	struct tps6594 *tps = dev_get_drvdata(dev->parent);
 	int ret;

 	ret = regmap_bulk_read(tps->regmap, TPS6594_REG_ALARM_SECONDS,
 			       alarm_data, NUM_TIME_ALARM_REGS);
 	if (ret < 0)
 		return ret;

 	alm->time.tm_sec = bcd2bin(alarm_data[0]);
 	alm->time.tm_min = bcd2bin(alarm_data[1]);
 	alm->time.tm_hour = bcd2bin(alarm_data[2]);
 	alm->time.tm_mday = bcd2bin(alarm_data[3]);
 	alm->time.tm_mon = bcd2bin(alarm_data[4]) - 1;
 	alm->time.tm_year = bcd2bin(alarm_data[5]) + 100;

 	ret = regmap_read(tps->regmap, TPS6594_REG_RTC_INTERRUPTS, &int_val);
 	if (ret < 0)
 		return ret;

 	alm->enabled = int_val & TPS6594_BIT_IT_ALARM;

 	return 0;
 }

 static int tps6594_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
 {
 	unsigned char alarm_data[NUM_TIME_ALARM_REGS];
 	struct tps6594 *tps = dev_get_drvdata(dev->parent);
 	int ret;

 	// Disable alarm irq before changing the alarm timestamp.
 	ret = tps6594_rtc_alarm_irq_enable(dev, 0);
 	if (ret)
 		return ret;

 	alarm_data[0] = bin2bcd(alm->time.tm_sec);
 	alarm_data[1] = bin2bcd(alm->time.tm_min);
 	alarm_data[2] = bin2bcd(alm->time.tm_hour);
 	alarm_data[3] = bin2bcd(alm->time.tm_mday);
 	alarm_data[4] = bin2bcd(alm->time.tm_mon + 1);
 	alarm_data[5] = bin2bcd(alm->time.tm_year - 100);

 	// Update all the alarm registers in one shot.
 	ret = regmap_bulk_write(tps->regmap, TPS6594_REG_ALARM_SECONDS,
 				alarm_data, NUM_TIME_ALARM_REGS);
 	if (ret < 0)
 		return ret;

 	if (alm->enabled)
 		ret = tps6594_rtc_alarm_irq_enable(dev, 1);

 	return ret;
 }

 static int tps6594_rtc_set_calibration(struct device *dev, int calibration)
 {
 	struct tps6594 *tps = dev_get_drvdata(dev->parent);
 	__le16 value;
 	int ret;

 	/*
 	 * TPS6594 uses two's complement 16 bit value for compensation of RTC
 	 * crystal inaccuracies. One time every hour when seconds counter
 	 * increments from 0 to 1 compensation value will be added to internal
 	 * RTC counter value.
 	 *
 	 * Valid range for compensation value: [-32767 .. 32767].
 	 */
 	if (calibration < S16_MIN + 1 || calibration > S16_MAX)
 		return -ERANGE;

 	value = cpu_to_le16(calibration);

 	// Update all the compensation registers in one shot.
 	ret = regmap_bulk_write(tps->regmap, TPS6594_REG_RTC_COMP_LSB, &value,
 				sizeof(value));
 	if (ret < 0)
 		return ret;

 	// Enable automatic compensation.
 	return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
 			       TPS6594_BIT_AUTO_COMP);
 }

 static int tps6594_rtc_get_calibration(struct device *dev, int *calibration)
 {
 	struct tps6594 *tps = dev_get_drvdata(dev->parent);
 	unsigned int ctrl;
 	__le16 value;
 	int ret;

 	ret = regmap_read(tps->regmap, TPS6594_REG_RTC_CTRL_1, &ctrl);
 	if (ret < 0)
 		return ret;

 	// If automatic compensation is not enabled report back zero.
 	if (!(ctrl & TPS6594_BIT_AUTO_COMP)) {
 		*calibration = 0;
 		return 0;
 	}

 	ret = regmap_bulk_read(tps->regmap, TPS6594_REG_RTC_COMP_LSB, &value,
 			       sizeof(value));
 	if (ret < 0)
 		return ret;

 	*calibration = le16_to_cpu(value);

 	return 0;
 }

 static int tps6594_rtc_read_offset(struct device *dev, long *offset)
 {
 	int calibration;
 	s64 tmp;
 	int ret;

 	ret = tps6594_rtc_get_calibration(dev, &calibration);
 	if (ret < 0)
 		return ret;

 	// Convert from RTC calibration register format to ppb format.
 	tmp = calibration * PPB_MULT;

 	if (tmp < 0)
 		tmp -= TICKS_PER_HOUR / 2LL;
 	else
 		tmp += TICKS_PER_HOUR / 2LL;
 	tmp = div_s64(tmp, TICKS_PER_HOUR);

 	/*
 	 * SAFETY:
 	 * Computatiion is the reverse operation of the one done in
 	 * `tps6594_rtc_set_offset`. The safety remarks applie here too.
 	 */

 	/*
 	 * Offset value operates in negative way, so swap sign.
 	 * See 8.3.10.5, (32768 - COMP_REG).
 	 */
 	*offset = (long)-tmp;

 	return 0;
 }

 static int tps6594_rtc_set_offset(struct device *dev, long offset)
 {
 	int calibration;
 	s64 tmp;

 	// Make sure offset value is within supported range.
 	if (offset < MIN_OFFSET || offset > MAX_OFFSET)
 		return -ERANGE;

 	// Convert from ppb format to RTC calibration register format.

 	tmp = offset * TICKS_PER_HOUR;
 	if (tmp < 0)
 		tmp -= PPB_MULT / 2LL;
 	else
 		tmp += PPB_MULT / 2LL;
 	tmp = div_s64(tmp, PPB_MULT);

 	/*
 	 * SAFETY:
 	 * - tmp = offset * TICK_PER_HOUR :
 	 *	`offset` can't be more than 277774, so `tmp` can't exceed 277774000000000
 	 *	which is lower than the maximum value in an `s64` (2^63-1). No overflow here.
 	 *
 	 * - tmp += TICK_PER_HOUR / 2LL :
 	 *	tmp will have a maximum value of 277774117964800 which is still inferior to 2^63-1.
 	 */

 	// Offset value operates in negative way, so swap sign.
 	calibration = (int)-tmp;

 	return tps6594_rtc_set_calibration(dev, calibration);
 }

 static irqreturn_t tps6594_rtc_interrupt(int irq, void *rtc)
 {
 	struct device *dev = rtc;
 	struct tps6594 *tps = dev_get_drvdata(dev->parent);
 	struct rtc_device *rtc_dev = dev_get_drvdata(dev);
 	int ret;
 	u32 rtc_reg;

 	ret = regmap_read(tps->regmap, TPS6594_REG_RTC_STATUS, &rtc_reg);
 	if (ret)
 		return IRQ_NONE;

 	rtc_update_irq(rtc_dev, 1, RTC_IRQF | RTC_AF);

 	return IRQ_HANDLED;
 }

 static const struct rtc_class_ops tps6594_rtc_ops = {
 	.read_time = tps6594_rtc_read_time,
 	.set_time = tps6594_rtc_set_time,
 	.read_alarm = tps6594_rtc_read_alarm,
 	.set_alarm = tps6594_rtc_set_alarm,
 	.alarm_irq_enable = tps6594_rtc_alarm_irq_enable,
 	.read_offset = tps6594_rtc_read_offset,
 	.set_offset = tps6594_rtc_set_offset,
 };

 static int tps6594_rtc_probe(struct platform_device *pdev)
 {
 	struct tps6594 *tps = dev_get_drvdata(pdev->dev.parent);
 	struct device *dev = &pdev->dev;
 	struct rtc_device *rtc;
 	int irq;
 	int ret;

 	rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL);
 	if (!rtc)
 		return -ENOMEM;

 	rtc = devm_rtc_allocate_device(dev);
 	if (IS_ERR(rtc))
 		return PTR_ERR(rtc);

 	// Enable crystal oscillator.
 	ret = regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_2,
 			      TPS6594_BIT_XTAL_EN);
 	if (ret < 0)
 		return ret;

 	ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
 			       TPS6594_BIT_RUN);
 	if (ret < 0)
 		return ret;
 	// RTC not running.
 	if (ret == 0) {
 		ret = regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
 				      TPS6594_BIT_STOP_RTC);
 		if (ret < 0)
 			return ret;

 		/*
 		 * On some boards, a 40 ms delay is needed before BIT_RUN is set.
 		 * 80 ms should provide sufficient margin.
 		 */
 		mdelay(80);

 		/*
 		 * RTC should be running now. Check if this is the case.
 		 * If not it might be a missing oscillator.
 		 */
 		ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
 				       TPS6594_BIT_RUN);
 		if (ret < 0)
 			return ret;
 		if (ret == 0)
 			return -ENODEV;

 		// Stop RTC until first call to `tps6594_rtc_set_time`.
 		ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
 					TPS6594_BIT_STOP_RTC);
 		if (ret < 0)
 			return ret;
 	}

 	platform_set_drvdata(pdev, rtc);

 	irq = platform_get_irq_byname(pdev, TPS6594_IRQ_NAME_ALARM);
 	if (irq < 0)
 		return dev_err_probe(dev, irq, "Failed to get irq\n");

 	ret = devm_request_threaded_irq(dev, irq, NULL, tps6594_rtc_interrupt,
 					IRQF_ONESHOT, TPS6594_IRQ_NAME_ALARM,
 					dev);
 	if (ret < 0)
 		return dev_err_probe(dev, ret,
 				     "Failed to request_threaded_irq\n");

 	ret = device_init_wakeup(dev, true);
 	if (ret < 0)
 		return dev_err_probe(dev, ret,
 				     "Failed to init rtc as wakeup source\n");

 	rtc->ops = &tps6594_rtc_ops;
 	rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 	rtc->range_max = RTC_TIMESTAMP_END_2099;

 	return devm_rtc_register_device(rtc);
 }

 static const struct platform_device_id tps6594_rtc_id_table[] = {
 	{ "tps6594-rtc", },
 	{}
 };
 MODULE_DEVICE_TABLE(platform, tps6594_rtc_id_table);

 static struct platform_driver tps6594_rtc_driver = {
 	.probe		= tps6594_rtc_probe,
 	.driver		= {
 		.name	= "tps6594-rtc",
 	},
 	.id_table = tps6594_rtc_id_table,
 };

 module_platform_driver(tps6594_rtc_driver);
 MODULE_AUTHOR("Esteban Blanc <eblanc@baylibre.com>");
 MODULE_DESCRIPTION("TPS6594 RTC driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* RTC driver for tps6594 PMIC
	*
	* Copyright (C) 2023 BayLibre Incorporated - https://www.baylibre.com/
	*/

	#include <linux/bcd.h>
	#include <linux/errno.h>
	#include <linux/init.h>
	#include <linux/interrupt.h>
	#include <linux/kernel.h>
	#include <linux/limits.h>
	#include <linux/math64.h>
	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/mod_devicetable.h>
	#include <linux/property.h>
	#include <linux/rtc.h>
	#include <linux/types.h>
	#include <linux/units.h>

	#include <linux/mfd/tps6594.h>

	// Total number of RTC registers needed to set time
	#define NUM_TIME_REGS (TPS6594_REG_RTC_WEEKS - TPS6594_REG_RTC_SECONDS + 1)

	// Total number of RTC alarm registers
	#define NUM_TIME_ALARM_REGS (NUM_TIME_REGS - 1)

	/*
	* Min and max values supported by 'offset' interface (swapped sign).
	* After conversion, the values do not exceed the range [-32767, 33767]
	* which COMP_REG must conform to.
	*/
	#define MIN_OFFSET (-277774)
	#define MAX_OFFSET (277774)

	// Number of ticks per hour
	#define TICKS_PER_HOUR (32768 * 3600)

	// Multiplier for ppb conversions
	#define PPB_MULT NANO

	static int tps6594_rtc_alarm_irq_enable(struct device *dev,
	unsigned int enabled)
	{
	struct tps6594 *tps = dev_get_drvdata(dev->parent);
	u8 val;

	val = enabled ? TPS6594_BIT_IT_ALARM : 0;

	return regmap_update_bits(tps->regmap, TPS6594_REG_RTC_INTERRUPTS,
	TPS6594_BIT_IT_ALARM, val);
	}

	/* Pulse GET_TIME field of RTC_CTRL_1 to store a timestamp in shadow registers. */
	static int tps6594_rtc_shadow_timestamp(struct device dev, struct tps6594 tps)
	{
	int ret;

	/*
	* Set GET_TIME to 0. Next time we set GET_TIME to 1 we will be sure to store
	* an up-to-date timestamp.
	*/
	ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
	TPS6594_BIT_GET_TIME);
	if (ret < 0)
	return ret;

	/*
	* Copy content of RTC registers to shadow registers or latches to read
	* a coherent timestamp.
	*/
	return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
	TPS6594_BIT_GET_TIME);
	}

	static int tps6594_rtc_read_time(struct device dev, struct rtc_time tm)
	{
	unsigned char rtc_data[NUM_TIME_REGS];
	struct tps6594 *tps = dev_get_drvdata(dev->parent);
	int ret;

	// Check if RTC is running.
	ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
	TPS6594_BIT_RUN);
	if (ret < 0)
	return ret;
	if (ret == 0)
	return -EINVAL;

	ret = tps6594_rtc_shadow_timestamp(dev, tps);
	if (ret < 0)
	return ret;

	// Read shadowed RTC registers.
	ret = regmap_bulk_read(tps->regmap, TPS6594_REG_RTC_SECONDS, rtc_data,
	NUM_TIME_REGS);
	if (ret < 0)
	return ret;

	tm->tm_sec = bcd2bin(rtc_data[0]);
	tm->tm_min = bcd2bin(rtc_data[1]);
	tm->tm_hour = bcd2bin(rtc_data[2]);
	tm->tm_mday = bcd2bin(rtc_data[3]);
	tm->tm_mon = bcd2bin(rtc_data[4]) - 1;
	tm->tm_year = bcd2bin(rtc_data[5]) + 100;
	tm->tm_wday = bcd2bin(rtc_data[6]);

	return 0;
	}

	static int tps6594_rtc_set_time(struct device dev, struct rtc_time tm)
	{
	unsigned char rtc_data[NUM_TIME_REGS];
	struct tps6594 *tps = dev_get_drvdata(dev->parent);
	int ret;

	rtc_data[0] = bin2bcd(tm->tm_sec);
	rtc_data[1] = bin2bcd(tm->tm_min);
	rtc_data[2] = bin2bcd(tm->tm_hour);
	rtc_data[3] = bin2bcd(tm->tm_mday);
	rtc_data[4] = bin2bcd(tm->tm_mon + 1);
	rtc_data[5] = bin2bcd(tm->tm_year - 100);
	rtc_data[6] = bin2bcd(tm->tm_wday);

	// Stop RTC while updating the RTC time registers.
	ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
	TPS6594_BIT_STOP_RTC);
	if (ret < 0)
	return ret;

	// Update all the time registers in one shot.
	ret = regmap_bulk_write(tps->regmap, TPS6594_REG_RTC_SECONDS, rtc_data,
	NUM_TIME_REGS);
	if (ret < 0)
	return ret;

	// Start back RTC.
	return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
	TPS6594_BIT_STOP_RTC);
	}

	static int tps6594_rtc_read_alarm(struct device dev, struct rtc_wkalrm alm)
	{
	unsigned char alarm_data[NUM_TIME_ALARM_REGS];
	u32 int_val;
	struct tps6594 *tps = dev_get_drvdata(dev->parent);
	int ret;

	ret = regmap_bulk_read(tps->regmap, TPS6594_REG_ALARM_SECONDS,
	alarm_data, NUM_TIME_ALARM_REGS);
	if (ret < 0)
	return ret;

	alm->time.tm_sec = bcd2bin(alarm_data[0]);
	alm->time.tm_min = bcd2bin(alarm_data[1]);
	alm->time.tm_hour = bcd2bin(alarm_data[2]);
	alm->time.tm_mday = bcd2bin(alarm_data[3]);
	alm->time.tm_mon = bcd2bin(alarm_data[4]) - 1;
	alm->time.tm_year = bcd2bin(alarm_data[5]) + 100;

	ret = regmap_read(tps->regmap, TPS6594_REG_RTC_INTERRUPTS, &int_val);
	if (ret < 0)
	return ret;

	alm->enabled = int_val & TPS6594_BIT_IT_ALARM;

	return 0;
	}

	static int tps6594_rtc_set_alarm(struct device dev, struct rtc_wkalrm alm)
	{
	unsigned char alarm_data[NUM_TIME_ALARM_REGS];
	struct tps6594 *tps = dev_get_drvdata(dev->parent);
	int ret;

	// Disable alarm irq before changing the alarm timestamp.
	ret = tps6594_rtc_alarm_irq_enable(dev, 0);
	if (ret)
	return ret;

	alarm_data[0] = bin2bcd(alm->time.tm_sec);
	alarm_data[1] = bin2bcd(alm->time.tm_min);
	alarm_data[2] = bin2bcd(alm->time.tm_hour);
	alarm_data[3] = bin2bcd(alm->time.tm_mday);
	alarm_data[4] = bin2bcd(alm->time.tm_mon + 1);
	alarm_data[5] = bin2bcd(alm->time.tm_year - 100);

	// Update all the alarm registers in one shot.
	ret = regmap_bulk_write(tps->regmap, TPS6594_REG_ALARM_SECONDS,
	alarm_data, NUM_TIME_ALARM_REGS);
	if (ret < 0)
	return ret;

	if (alm->enabled)
	ret = tps6594_rtc_alarm_irq_enable(dev, 1);

	return ret;
	}

	static int tps6594_rtc_set_calibration(struct device *dev, int calibration)
	{
	struct tps6594 *tps = dev_get_drvdata(dev->parent);
	__le16 value;
	int ret;

	/*
	* TPS6594 uses two's complement 16 bit value for compensation of RTC
	* crystal inaccuracies. One time every hour when seconds counter
	* increments from 0 to 1 compensation value will be added to internal
	* RTC counter value.
	*
	* Valid range for compensation value: [-32767 .. 32767].
	*/
	if (calibration < S16_MIN + 1 \|\| calibration > S16_MAX)
	return -ERANGE;

	value = cpu_to_le16(calibration);

	// Update all the compensation registers in one shot.
	ret = regmap_bulk_write(tps->regmap, TPS6594_REG_RTC_COMP_LSB, &value,
	sizeof(value));
	if (ret < 0)
	return ret;

	// Enable automatic compensation.
	return regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
	TPS6594_BIT_AUTO_COMP);
	}

	static int tps6594_rtc_get_calibration(struct device dev, int calibration)
	{
	struct tps6594 *tps = dev_get_drvdata(dev->parent);
	unsigned int ctrl;
	__le16 value;
	int ret;

	ret = regmap_read(tps->regmap, TPS6594_REG_RTC_CTRL_1, &ctrl);
	if (ret < 0)
	return ret;

	// If automatic compensation is not enabled report back zero.
	if (!(ctrl & TPS6594_BIT_AUTO_COMP)) {
	*calibration = 0;
	return 0;
	}

	ret = regmap_bulk_read(tps->regmap, TPS6594_REG_RTC_COMP_LSB, &value,
	sizeof(value));
	if (ret < 0)
	return ret;

	*calibration = le16_to_cpu(value);

	return 0;
	}

	static int tps6594_rtc_read_offset(struct device dev, long offset)
	{
	int calibration;
	s64 tmp;
	int ret;

	ret = tps6594_rtc_get_calibration(dev, &calibration);
	if (ret < 0)
	return ret;

	// Convert from RTC calibration register format to ppb format.
	tmp = calibration * PPB_MULT;

	if (tmp < 0)
	tmp -= TICKS_PER_HOUR / 2LL;
	else
	tmp += TICKS_PER_HOUR / 2LL;
	tmp = div_s64(tmp, TICKS_PER_HOUR);

	/*
	* SAFETY:
	* Computatiion is the reverse operation of the one done in
	* `tps6594_rtc_set_offset`. The safety remarks applie here too.
	*/

	/*
	* Offset value operates in negative way, so swap sign.
	* See 8.3.10.5, (32768 - COMP_REG).
	*/
	*offset = (long)-tmp;

	return 0;
	}

	static int tps6594_rtc_set_offset(struct device *dev, long offset)
	{
	int calibration;
	s64 tmp;

	// Make sure offset value is within supported range.
	if (offset < MIN_OFFSET \|\| offset > MAX_OFFSET)
	return -ERANGE;

	// Convert from ppb format to RTC calibration register format.

	tmp = offset * TICKS_PER_HOUR;
	if (tmp < 0)
	tmp -= PPB_MULT / 2LL;
	else
	tmp += PPB_MULT / 2LL;
	tmp = div_s64(tmp, PPB_MULT);

	/*
	* SAFETY:
	* - tmp = offset * TICK_PER_HOUR :
	* `offset` can't be more than 277774, so `tmp` can't exceed 277774000000000
	* which is lower than the maximum value in an `s64` (2^63-1). No overflow here.
	*
	* - tmp += TICK_PER_HOUR / 2LL :
	* tmp will have a maximum value of 277774117964800 which is still inferior to 2^63-1.
	*/

	// Offset value operates in negative way, so swap sign.
	calibration = (int)-tmp;

	return tps6594_rtc_set_calibration(dev, calibration);
	}

	static irqreturn_t tps6594_rtc_interrupt(int irq, void *rtc)
	{
	struct device *dev = rtc;
	struct tps6594 *tps = dev_get_drvdata(dev->parent);
	struct rtc_device *rtc_dev = dev_get_drvdata(dev);
	int ret;
	u32 rtc_reg;

	ret = regmap_read(tps->regmap, TPS6594_REG_RTC_STATUS, &rtc_reg);
	if (ret)
	return IRQ_NONE;

	rtc_update_irq(rtc_dev, 1, RTC_IRQF \| RTC_AF);

	return IRQ_HANDLED;
	}

	static const struct rtc_class_ops tps6594_rtc_ops = {
	.read_time = tps6594_rtc_read_time,
	.set_time = tps6594_rtc_set_time,
	.read_alarm = tps6594_rtc_read_alarm,
	.set_alarm = tps6594_rtc_set_alarm,
	.alarm_irq_enable = tps6594_rtc_alarm_irq_enable,
	.read_offset = tps6594_rtc_read_offset,
	.set_offset = tps6594_rtc_set_offset,
	};

	static int tps6594_rtc_probe(struct platform_device *pdev)
	{
	struct tps6594 *tps = dev_get_drvdata(pdev->dev.parent);
	struct device *dev = &pdev->dev;
	struct rtc_device *rtc;
	int irq;
	int ret;

	rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL);
	if (!rtc)
	return -ENOMEM;

	rtc = devm_rtc_allocate_device(dev);
	if (IS_ERR(rtc))
	return PTR_ERR(rtc);

	// Enable crystal oscillator.
	ret = regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_2,
	TPS6594_BIT_XTAL_EN);
	if (ret < 0)
	return ret;

	ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
	TPS6594_BIT_RUN);
	if (ret < 0)
	return ret;
	// RTC not running.
	if (ret == 0) {
	ret = regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
	TPS6594_BIT_STOP_RTC);
	if (ret < 0)
	return ret;

	/*
	* On some boards, a 40 ms delay is needed before BIT_RUN is set.
	* 80 ms should provide sufficient margin.
	*/
	mdelay(80);

	/*
	* RTC should be running now. Check if this is the case.
	* If not it might be a missing oscillator.
	*/
	ret = regmap_test_bits(tps->regmap, TPS6594_REG_RTC_STATUS,
	TPS6594_BIT_RUN);
	if (ret < 0)
	return ret;
	if (ret == 0)
	return -ENODEV;

	// Stop RTC until first call to `tps6594_rtc_set_time`.
	ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
	TPS6594_BIT_STOP_RTC);
	if (ret < 0)
	return ret;
	}

	platform_set_drvdata(pdev, rtc);

	irq = platform_get_irq_byname(pdev, TPS6594_IRQ_NAME_ALARM);
	if (irq < 0)
	return dev_err_probe(dev, irq, "Failed to get irq\n");

	ret = devm_request_threaded_irq(dev, irq, NULL, tps6594_rtc_interrupt,
	IRQF_ONESHOT, TPS6594_IRQ_NAME_ALARM,
	dev);
	if (ret < 0)
	return dev_err_probe(dev, ret,
	"Failed to request_threaded_irq\n");

	ret = device_init_wakeup(dev, true);
	if (ret < 0)
	return dev_err_probe(dev, ret,
	"Failed to init rtc as wakeup source\n");

	rtc->ops = &tps6594_rtc_ops;
	rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
	rtc->range_max = RTC_TIMESTAMP_END_2099;

	return devm_rtc_register_device(rtc);
	}

	static const struct platform_device_id tps6594_rtc_id_table[] = {
	{ "tps6594-rtc", },
	{}
	};
	MODULE_DEVICE_TABLE(platform, tps6594_rtc_id_table);

	static struct platform_driver tps6594_rtc_driver = {
	.probe = tps6594_rtc_probe,
	.driver = {
	.name = "tps6594-rtc",
	},
	.id_table = tps6594_rtc_id_table,
	};

	module_platform_driver(tps6594_rtc_driver);
	MODULE_AUTHOR("Esteban Blanc <eblanc@baylibre.com>");
	MODULE_DESCRIPTION("TPS6594 RTC driver");
	MODULE_LICENSE("GPL");