drivers/rtc/rtc-88pm860x.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Real Time Clock driver for Marvell 88PM860x PMIC
  *
  * Copyright (c) 2010 Marvell International Ltd.
  * Author:	Haojian Zhuang <haojian.zhuang@marvell.com>
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/mutex.h>
 #include <linux/rtc.h>
 #include <linux/delay.h>
 #include <linux/mfd/core.h>
 #include <linux/mfd/88pm860x.h>

 #define VRTC_CALIBRATION

 struct pm860x_rtc_info {
 	struct pm860x_chip	*chip;
 	struct i2c_client	*i2c;
 	struct rtc_device	*rtc_dev;
 	struct device		*dev;
 	struct delayed_work	calib_work;

 	int			irq;
 	int			vrtc;
 };

 #define REG_VRTC_MEAS1		0x7D

 #define REG0_ADDR		0xB0
 #define REG1_ADDR		0xB2
 #define REG2_ADDR		0xB4
 #define REG3_ADDR		0xB6

 #define REG0_DATA		0xB1
 #define REG1_DATA		0xB3
 #define REG2_DATA		0xB5
 #define REG3_DATA		0xB7

 /* bit definitions of Measurement Enable Register 2 (0x51) */
 #define MEAS2_VRTC		(1 << 0)

 /* bit definitions of RTC Register 1 (0xA0) */
 #define ALARM_EN		(1 << 3)
 #define ALARM_WAKEUP		(1 << 4)
 #define ALARM			(1 << 5)
 #define RTC1_USE_XO		(1 << 7)

 #define VRTC_CALIB_INTERVAL	(HZ * 60 * 10)		/* 10 minutes */

 static irqreturn_t rtc_update_handler(int irq, void *data)
 {
 	struct pm860x_rtc_info *info = (struct pm860x_rtc_info *)data;
 	int mask;

 	mask = ALARM | ALARM_WAKEUP;
 	pm860x_set_bits(info->i2c, PM8607_RTC1, mask | ALARM_EN, mask);
 	rtc_update_irq(info->rtc_dev, 1, RTC_AF);
 	return IRQ_HANDLED;
 }

 static int pm860x_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
 {
 	struct pm860x_rtc_info *info = dev_get_drvdata(dev);

 	if (enabled)
 		pm860x_set_bits(info->i2c, PM8607_RTC1, ALARM_EN, ALARM_EN);
 	else
 		pm860x_set_bits(info->i2c, PM8607_RTC1, ALARM_EN, 0);
 	return 0;
 }

 static int pm860x_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct pm860x_rtc_info *info = dev_get_drvdata(dev);
 	unsigned char buf[8];
 	unsigned long ticks, base, data;

 	pm860x_page_bulk_read(info->i2c, REG0_ADDR, 8, buf);
 	dev_dbg(info->dev, "%x-%x-%x-%x-%x-%x-%x-%x\n", buf[0], buf[1],
 		buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
 	base = ((unsigned long)buf[1] << 24) | (buf[3] << 16) |
 		(buf[5] << 8) | buf[7];

 	/* load 32-bit read-only counter */
 	pm860x_bulk_read(info->i2c, PM8607_RTC_COUNTER1, 4, buf);
 	data = ((unsigned long)buf[3] << 24) | (buf[2] << 16) |
 		(buf[1] << 8) | buf[0];
 	ticks = base + data;
 	dev_dbg(info->dev, "get base:0x%lx, RO count:0x%lx, ticks:0x%lx\n",
 		base, data, ticks);

 	rtc_time64_to_tm(ticks, tm);

 	return 0;
 }

 static int pm860x_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct pm860x_rtc_info *info = dev_get_drvdata(dev);
 	unsigned char buf[4];
 	unsigned long ticks, base, data;

 	ticks = rtc_tm_to_time64(tm);

 	/* load 32-bit read-only counter */
 	pm860x_bulk_read(info->i2c, PM8607_RTC_COUNTER1, 4, buf);
 	data = ((unsigned long)buf[3] << 24) | (buf[2] << 16) |
 		(buf[1] << 8) | buf[0];
 	base = ticks - data;
 	dev_dbg(info->dev, "set base:0x%lx, RO count:0x%lx, ticks:0x%lx\n",
 		base, data, ticks);

 	pm860x_page_reg_write(info->i2c, REG0_DATA, (base >> 24) & 0xFF);
 	pm860x_page_reg_write(info->i2c, REG1_DATA, (base >> 16) & 0xFF);
 	pm860x_page_reg_write(info->i2c, REG2_DATA, (base >> 8) & 0xFF);
 	pm860x_page_reg_write(info->i2c, REG3_DATA, base & 0xFF);

 	return 0;
 }

 static int pm860x_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct pm860x_rtc_info *info = dev_get_drvdata(dev);
 	unsigned char buf[8];
 	unsigned long ticks, base, data;
 	int ret;

 	pm860x_page_bulk_read(info->i2c, REG0_ADDR, 8, buf);
 	dev_dbg(info->dev, "%x-%x-%x-%x-%x-%x-%x-%x\n", buf[0], buf[1],
 		buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
 	base = ((unsigned long)buf[1] << 24) | (buf[3] << 16) |
 		(buf[5] << 8) | buf[7];

 	pm860x_bulk_read(info->i2c, PM8607_RTC_EXPIRE1, 4, buf);
 	data = ((unsigned long)buf[3] << 24) | (buf[2] << 16) |
 		(buf[1] << 8) | buf[0];
 	ticks = base + data;
 	dev_dbg(info->dev, "get base:0x%lx, RO count:0x%lx, ticks:0x%lx\n",
 		base, data, ticks);

 	rtc_time64_to_tm(ticks, &alrm->time);
 	ret = pm860x_reg_read(info->i2c, PM8607_RTC1);
 	alrm->enabled = (ret & ALARM_EN) ? 1 : 0;
 	alrm->pending = (ret & (ALARM | ALARM_WAKEUP)) ? 1 : 0;
 	return 0;
 }

 static int pm860x_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct pm860x_rtc_info *info = dev_get_drvdata(dev);
 	unsigned long ticks, base, data;
 	unsigned char buf[8];
 	int mask;

 	pm860x_set_bits(info->i2c, PM8607_RTC1, ALARM_EN, 0);

 	pm860x_page_bulk_read(info->i2c, REG0_ADDR, 8, buf);
 	dev_dbg(info->dev, "%x-%x-%x-%x-%x-%x-%x-%x\n", buf[0], buf[1],
 		buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
 	base = ((unsigned long)buf[1] << 24) | (buf[3] << 16) |
 		(buf[5] << 8) | buf[7];

 	ticks = rtc_tm_to_time64(&alrm->time);
 	data = ticks - base;

 	buf[0] = data & 0xff;
 	buf[1] = (data >> 8) & 0xff;
 	buf[2] = (data >> 16) & 0xff;
 	buf[3] = (data >> 24) & 0xff;
 	pm860x_bulk_write(info->i2c, PM8607_RTC_EXPIRE1, 4, buf);
 	if (alrm->enabled) {
 		mask = ALARM | ALARM_WAKEUP | ALARM_EN;
 		pm860x_set_bits(info->i2c, PM8607_RTC1, mask, mask);
 	} else {
 		mask = ALARM | ALARM_WAKEUP | ALARM_EN;
 		pm860x_set_bits(info->i2c, PM8607_RTC1, mask,
 				ALARM | ALARM_WAKEUP);
 	}
 	return 0;
 }

 static const struct rtc_class_ops pm860x_rtc_ops = {
 	.read_time	= pm860x_rtc_read_time,
 	.set_time	= pm860x_rtc_set_time,
 	.read_alarm	= pm860x_rtc_read_alarm,
 	.set_alarm	= pm860x_rtc_set_alarm,
 	.alarm_irq_enable = pm860x_rtc_alarm_irq_enable,
 };

 #ifdef VRTC_CALIBRATION
 static void calibrate_vrtc_work(struct work_struct *work)
 {
 	struct pm860x_rtc_info *info = container_of(work,
 		struct pm860x_rtc_info, calib_work.work);
 	unsigned char buf[2];
 	unsigned int sum, data, mean, vrtc_set;
 	int i;

 	for (i = 0, sum = 0; i < 16; i++) {
 		msleep(100);
 		pm860x_bulk_read(info->i2c, REG_VRTC_MEAS1, 2, buf);
 		data = (buf[0] << 4) | buf[1];
 		data = (data * 5400) >> 12;	/* convert to mv */
 		sum += data;
 	}
 	mean = sum >> 4;
 	vrtc_set = 2700 + (info->vrtc & 0x3) * 200;
 	dev_dbg(info->dev, "mean:%d, vrtc_set:%d\n", mean, vrtc_set);

 	sum = pm860x_reg_read(info->i2c, PM8607_RTC_MISC1);
 	data = sum & 0x3;
 	if ((mean + 200) < vrtc_set) {
 		/* try higher voltage */
 		if (++data == 4)
 			goto out;
 		data = (sum & 0xf8) | (data & 0x3);
 		pm860x_reg_write(info->i2c, PM8607_RTC_MISC1, data);
 	} else if ((mean - 200) > vrtc_set) {
 		/* try lower voltage */
 		if (data-- == 0)
 			goto out;
 		data = (sum & 0xf8) | (data & 0x3);
 		pm860x_reg_write(info->i2c, PM8607_RTC_MISC1, data);
 	} else
 		goto out;
 	dev_dbg(info->dev, "set 0x%x to RTC_MISC1\n", data);
 	/* trigger next calibration since VRTC is updated */
 	schedule_delayed_work(&info->calib_work, VRTC_CALIB_INTERVAL);
 	return;
 out:
 	/* disable measurement */
 	pm860x_set_bits(info->i2c, PM8607_MEAS_EN2, MEAS2_VRTC, 0);
 	dev_dbg(info->dev, "finish VRTC calibration\n");
 	return;
 }
 #endif

 #ifdef CONFIG_OF
 static int pm860x_rtc_dt_init(struct platform_device *pdev,
 			      struct pm860x_rtc_info *info)
 {
 	struct device_node *np = pdev->dev.parent->of_node;
 	int ret;
 	if (!np)
 		return -ENODEV;
 	np = of_get_child_by_name(np, "rtc");
 	if (!np) {
 		dev_err(&pdev->dev, "failed to find rtc node\n");
 		return -ENODEV;
 	}
 	ret = of_property_read_u32(np, "marvell,88pm860x-vrtc", &info->vrtc);
 	if (ret)
 		info->vrtc = 0;
 	of_node_put(np);
 	return 0;
 }
 #else
 #define pm860x_rtc_dt_init(x, y)	do { } while (0)
 #endif

 static int pm860x_rtc_probe(struct platform_device *pdev)
 {
 	struct pm860x_chip *chip = dev_get_drvdata(pdev->dev.parent);
 	struct pm860x_rtc_info *info;
 	int ret;

 	info = devm_kzalloc(&pdev->dev, sizeof(struct pm860x_rtc_info),
 			    GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;
 	info->irq = platform_get_irq(pdev, 0);
 	if (info->irq < 0)
 		return info->irq;

 	info->chip = chip;
 	info->i2c = (chip->id == CHIP_PM8607) ? chip->client : chip->companion;
 	info->dev = &pdev->dev;
 	dev_set_drvdata(&pdev->dev, info);

 	info->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
 	if (IS_ERR(info->rtc_dev))
 		return PTR_ERR(info->rtc_dev);

 	ret = devm_request_threaded_irq(&pdev->dev, info->irq, NULL,
 					rtc_update_handler, IRQF_ONESHOT, "rtc",
 					info);
 	if (ret < 0) {
 		dev_err(chip->dev, "Failed to request IRQ: #%d: %d\n",
 			info->irq, ret);
 		return ret;
 	}

 	/* set addresses of 32-bit base value for RTC time */
 	pm860x_page_reg_write(info->i2c, REG0_ADDR, REG0_DATA);
 	pm860x_page_reg_write(info->i2c, REG1_ADDR, REG1_DATA);
 	pm860x_page_reg_write(info->i2c, REG2_ADDR, REG2_DATA);
 	pm860x_page_reg_write(info->i2c, REG3_ADDR, REG3_DATA);

 	pm860x_rtc_dt_init(pdev, info);

 	info->rtc_dev->ops = &pm860x_rtc_ops;
 	info->rtc_dev->range_max = U32_MAX;

 	ret = devm_rtc_register_device(info->rtc_dev);
 	if (ret)
 		return ret;

 	/*
 	 * enable internal XO instead of internal 3.25MHz clock since it can
 	 * free running in PMIC power-down state.
 	 */
 	pm860x_set_bits(info->i2c, PM8607_RTC1, RTC1_USE_XO, RTC1_USE_XO);

 #ifdef VRTC_CALIBRATION
 	/* <00> -- 2.7V, <01> -- 2.9V, <10> -- 3.1V, <11> -- 3.3V */
 	pm860x_set_bits(info->i2c, PM8607_MEAS_EN2, MEAS2_VRTC, MEAS2_VRTC);

 	/* calibrate VRTC */
 	INIT_DELAYED_WORK(&info->calib_work, calibrate_vrtc_work);
 	schedule_delayed_work(&info->calib_work, VRTC_CALIB_INTERVAL);
 #endif	/* VRTC_CALIBRATION */

 	device_init_wakeup(&pdev->dev, 1);

 	return 0;
 }

 static int pm860x_rtc_remove(struct platform_device *pdev)
 {
 	struct pm860x_rtc_info *info = platform_get_drvdata(pdev);

 #ifdef VRTC_CALIBRATION
 	cancel_delayed_work_sync(&info->calib_work);
 	/* disable measurement */
 	pm860x_set_bits(info->i2c, PM8607_MEAS_EN2, MEAS2_VRTC, 0);
 #endif	/* VRTC_CALIBRATION */

 	return 0;
 }

 #ifdef CONFIG_PM_SLEEP
 static int pm860x_rtc_suspend(struct device *dev)
 {
 	struct platform_device *pdev = to_platform_device(dev);
 	struct pm860x_chip *chip = dev_get_drvdata(pdev->dev.parent);

 	if (device_may_wakeup(dev))
 		chip->wakeup_flag |= 1 << PM8607_IRQ_RTC;
 	return 0;
 }
 static int pm860x_rtc_resume(struct device *dev)
 {
 	struct platform_device *pdev = to_platform_device(dev);
 	struct pm860x_chip *chip = dev_get_drvdata(pdev->dev.parent);

 	if (device_may_wakeup(dev))
 		chip->wakeup_flag &= ~(1 << PM8607_IRQ_RTC);
 	return 0;
 }
 #endif

 static SIMPLE_DEV_PM_OPS(pm860x_rtc_pm_ops, pm860x_rtc_suspend, pm860x_rtc_resume);

 static struct platform_driver pm860x_rtc_driver = {
 	.driver		= {
 		.name	= "88pm860x-rtc",
 		.pm	= &pm860x_rtc_pm_ops,
 	},
 	.probe		= pm860x_rtc_probe,
 	.remove		= pm860x_rtc_remove,
 };

 module_platform_driver(pm860x_rtc_driver);

 MODULE_DESCRIPTION("Marvell 88PM860x RTC driver");
 MODULE_AUTHOR("Haojian Zhuang <haojian.zhuang@marvell.com>");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Real Time Clock driver for Marvell 88PM860x PMIC
	*
	* Copyright (c) 2010 Marvell International Ltd.
	* Author: Haojian Zhuang <haojian.zhuang@marvell.com>
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/slab.h>
	#include <linux/mutex.h>
	#include <linux/rtc.h>
	#include <linux/delay.h>
	#include <linux/mfd/core.h>
	#include <linux/mfd/88pm860x.h>

	#define VRTC_CALIBRATION

	struct pm860x_rtc_info {
	struct pm860x_chip *chip;
	struct i2c_client *i2c;
	struct rtc_device *rtc_dev;
	struct device *dev;
	struct delayed_work calib_work;

	int irq;
	int vrtc;
	};

	#define REG_VRTC_MEAS1 0x7D

	#define REG0_ADDR 0xB0
	#define REG1_ADDR 0xB2
	#define REG2_ADDR 0xB4
	#define REG3_ADDR 0xB6

	#define REG0_DATA 0xB1
	#define REG1_DATA 0xB3
	#define REG2_DATA 0xB5
	#define REG3_DATA 0xB7

	/* bit definitions of Measurement Enable Register 2 (0x51) */
	#define MEAS2_VRTC (1 << 0)

	/* bit definitions of RTC Register 1 (0xA0) */
	#define ALARM_EN (1 << 3)
	#define ALARM_WAKEUP (1 << 4)
	#define ALARM (1 << 5)
	#define RTC1_USE_XO (1 << 7)

	#define VRTC_CALIB_INTERVAL (HZ * 60 * 10) /* 10 minutes */

	static irqreturn_t rtc_update_handler(int irq, void *data)
	{
	struct pm860x_rtc_info info = (struct pm860x_rtc_info )data;
	int mask;

	mask = ALARM \| ALARM_WAKEUP;
	pm860x_set_bits(info->i2c, PM8607_RTC1, mask \| ALARM_EN, mask);
	rtc_update_irq(info->rtc_dev, 1, RTC_AF);
	return IRQ_HANDLED;
	}

	static int pm860x_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
	{
	struct pm860x_rtc_info *info = dev_get_drvdata(dev);

	if (enabled)
	pm860x_set_bits(info->i2c, PM8607_RTC1, ALARM_EN, ALARM_EN);
	else
	pm860x_set_bits(info->i2c, PM8607_RTC1, ALARM_EN, 0);
	return 0;
	}

	static int pm860x_rtc_read_time(struct device dev, struct rtc_time tm)
	{
	struct pm860x_rtc_info *info = dev_get_drvdata(dev);
	unsigned char buf[8];
	unsigned long ticks, base, data;

	pm860x_page_bulk_read(info->i2c, REG0_ADDR, 8, buf);
	dev_dbg(info->dev, "%x-%x-%x-%x-%x-%x-%x-%x\n", buf[0], buf[1],
	buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
	base = ((unsigned long)buf[1] << 24) \| (buf[3] << 16) \|
	(buf[5] << 8) \| buf[7];

	/* load 32-bit read-only counter */
	pm860x_bulk_read(info->i2c, PM8607_RTC_COUNTER1, 4, buf);
	data = ((unsigned long)buf[3] << 24) \| (buf[2] << 16) \|
	(buf[1] << 8) \| buf[0];
	ticks = base + data;
	dev_dbg(info->dev, "get base:0x%lx, RO count:0x%lx, ticks:0x%lx\n",
	base, data, ticks);

	rtc_time64_to_tm(ticks, tm);

	return 0;
	}

	static int pm860x_rtc_set_time(struct device dev, struct rtc_time tm)
	{
	struct pm860x_rtc_info *info = dev_get_drvdata(dev);
	unsigned char buf[4];
	unsigned long ticks, base, data;

	ticks = rtc_tm_to_time64(tm);

	/* load 32-bit read-only counter */
	pm860x_bulk_read(info->i2c, PM8607_RTC_COUNTER1, 4, buf);
	data = ((unsigned long)buf[3] << 24) \| (buf[2] << 16) \|
	(buf[1] << 8) \| buf[0];
	base = ticks - data;
	dev_dbg(info->dev, "set base:0x%lx, RO count:0x%lx, ticks:0x%lx\n",
	base, data, ticks);

	pm860x_page_reg_write(info->i2c, REG0_DATA, (base >> 24) & 0xFF);
	pm860x_page_reg_write(info->i2c, REG1_DATA, (base >> 16) & 0xFF);
	pm860x_page_reg_write(info->i2c, REG2_DATA, (base >> 8) & 0xFF);
	pm860x_page_reg_write(info->i2c, REG3_DATA, base & 0xFF);

	return 0;
	}

	static int pm860x_rtc_read_alarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct pm860x_rtc_info *info = dev_get_drvdata(dev);
	unsigned char buf[8];
	unsigned long ticks, base, data;
	int ret;

	pm860x_page_bulk_read(info->i2c, REG0_ADDR, 8, buf);
	dev_dbg(info->dev, "%x-%x-%x-%x-%x-%x-%x-%x\n", buf[0], buf[1],
	buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
	base = ((unsigned long)buf[1] << 24) \| (buf[3] << 16) \|
	(buf[5] << 8) \| buf[7];

	pm860x_bulk_read(info->i2c, PM8607_RTC_EXPIRE1, 4, buf);
	data = ((unsigned long)buf[3] << 24) \| (buf[2] << 16) \|
	(buf[1] << 8) \| buf[0];
	ticks = base + data;
	dev_dbg(info->dev, "get base:0x%lx, RO count:0x%lx, ticks:0x%lx\n",
	base, data, ticks);

	rtc_time64_to_tm(ticks, &alrm->time);
	ret = pm860x_reg_read(info->i2c, PM8607_RTC1);
	alrm->enabled = (ret & ALARM_EN) ? 1 : 0;
	alrm->pending = (ret & (ALARM \| ALARM_WAKEUP)) ? 1 : 0;
	return 0;
	}

	static int pm860x_rtc_set_alarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct pm860x_rtc_info *info = dev_get_drvdata(dev);
	unsigned long ticks, base, data;
	unsigned char buf[8];
	int mask;

	pm860x_set_bits(info->i2c, PM8607_RTC1, ALARM_EN, 0);

	pm860x_page_bulk_read(info->i2c, REG0_ADDR, 8, buf);
	dev_dbg(info->dev, "%x-%x-%x-%x-%x-%x-%x-%x\n", buf[0], buf[1],
	buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
	base = ((unsigned long)buf[1] << 24) \| (buf[3] << 16) \|
	(buf[5] << 8) \| buf[7];

	ticks = rtc_tm_to_time64(&alrm->time);
	data = ticks - base;

	buf[0] = data & 0xff;
	buf[1] = (data >> 8) & 0xff;
	buf[2] = (data >> 16) & 0xff;
	buf[3] = (data >> 24) & 0xff;
	pm860x_bulk_write(info->i2c, PM8607_RTC_EXPIRE1, 4, buf);
	if (alrm->enabled) {
	mask = ALARM \| ALARM_WAKEUP \| ALARM_EN;
	pm860x_set_bits(info->i2c, PM8607_RTC1, mask, mask);
	} else {
	mask = ALARM \| ALARM_WAKEUP \| ALARM_EN;
	pm860x_set_bits(info->i2c, PM8607_RTC1, mask,
	ALARM \| ALARM_WAKEUP);
	}
	return 0;
	}

	static const struct rtc_class_ops pm860x_rtc_ops = {
	.read_time = pm860x_rtc_read_time,
	.set_time = pm860x_rtc_set_time,
	.read_alarm = pm860x_rtc_read_alarm,
	.set_alarm = pm860x_rtc_set_alarm,
	.alarm_irq_enable = pm860x_rtc_alarm_irq_enable,
	};

	#ifdef VRTC_CALIBRATION
	static void calibrate_vrtc_work(struct work_struct *work)
	{
	struct pm860x_rtc_info *info = container_of(work,
	struct pm860x_rtc_info, calib_work.work);
	unsigned char buf[2];
	unsigned int sum, data, mean, vrtc_set;
	int i;

	for (i = 0, sum = 0; i < 16; i++) {
	msleep(100);
	pm860x_bulk_read(info->i2c, REG_VRTC_MEAS1, 2, buf);
	data = (buf[0] << 4) \| buf[1];
	data = (data * 5400) >> 12; /* convert to mv */
	sum += data;
	}
	mean = sum >> 4;
	vrtc_set = 2700 + (info->vrtc & 0x3) * 200;
	dev_dbg(info->dev, "mean:%d, vrtc_set:%d\n", mean, vrtc_set);

	sum = pm860x_reg_read(info->i2c, PM8607_RTC_MISC1);
	data = sum & 0x3;
	if ((mean + 200) < vrtc_set) {
	/* try higher voltage */
	if (++data == 4)
	goto out;
	data = (sum & 0xf8) \| (data & 0x3);
	pm860x_reg_write(info->i2c, PM8607_RTC_MISC1, data);
	} else if ((mean - 200) > vrtc_set) {
	/* try lower voltage */
	if (data-- == 0)
	goto out;
	data = (sum & 0xf8) \| (data & 0x3);
	pm860x_reg_write(info->i2c, PM8607_RTC_MISC1, data);
	} else
	goto out;
	dev_dbg(info->dev, "set 0x%x to RTC_MISC1\n", data);
	/* trigger next calibration since VRTC is updated */
	schedule_delayed_work(&info->calib_work, VRTC_CALIB_INTERVAL);
	return;
	out:
	/* disable measurement */
	pm860x_set_bits(info->i2c, PM8607_MEAS_EN2, MEAS2_VRTC, 0);
	dev_dbg(info->dev, "finish VRTC calibration\n");
	return;
	}
	#endif

	#ifdef CONFIG_OF
	static int pm860x_rtc_dt_init(struct platform_device *pdev,
	struct pm860x_rtc_info *info)
	{
	struct device_node *np = pdev->dev.parent->of_node;
	int ret;
	if (!np)
	return -ENODEV;
	np = of_get_child_by_name(np, "rtc");
	if (!np) {
	dev_err(&pdev->dev, "failed to find rtc node\n");
	return -ENODEV;
	}
	ret = of_property_read_u32(np, "marvell,88pm860x-vrtc", &info->vrtc);
	if (ret)
	info->vrtc = 0;
	of_node_put(np);
	return 0;
	}
	#else
	#define pm860x_rtc_dt_init(x, y) do { } while (0)
	#endif

	static int pm860x_rtc_probe(struct platform_device *pdev)
	{
	struct pm860x_chip *chip = dev_get_drvdata(pdev->dev.parent);
	struct pm860x_rtc_info *info;
	int ret;

	info = devm_kzalloc(&pdev->dev, sizeof(struct pm860x_rtc_info),
	GFP_KERNEL);
	if (!info)
	return -ENOMEM;
	info->irq = platform_get_irq(pdev, 0);
	if (info->irq < 0)
	return info->irq;

	info->chip = chip;
	info->i2c = (chip->id == CHIP_PM8607) ? chip->client : chip->companion;
	info->dev = &pdev->dev;
	dev_set_drvdata(&pdev->dev, info);

	info->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
	if (IS_ERR(info->rtc_dev))
	return PTR_ERR(info->rtc_dev);

	ret = devm_request_threaded_irq(&pdev->dev, info->irq, NULL,
	rtc_update_handler, IRQF_ONESHOT, "rtc",
	info);
	if (ret < 0) {
	dev_err(chip->dev, "Failed to request IRQ: #%d: %d\n",
	info->irq, ret);
	return ret;
	}

	/* set addresses of 32-bit base value for RTC time */
	pm860x_page_reg_write(info->i2c, REG0_ADDR, REG0_DATA);
	pm860x_page_reg_write(info->i2c, REG1_ADDR, REG1_DATA);
	pm860x_page_reg_write(info->i2c, REG2_ADDR, REG2_DATA);
	pm860x_page_reg_write(info->i2c, REG3_ADDR, REG3_DATA);

	pm860x_rtc_dt_init(pdev, info);

	info->rtc_dev->ops = &pm860x_rtc_ops;
	info->rtc_dev->range_max = U32_MAX;

	ret = devm_rtc_register_device(info->rtc_dev);
	if (ret)
	return ret;

	/*
	* enable internal XO instead of internal 3.25MHz clock since it can
	* free running in PMIC power-down state.
	*/
	pm860x_set_bits(info->i2c, PM8607_RTC1, RTC1_USE_XO, RTC1_USE_XO);

	#ifdef VRTC_CALIBRATION
	/* <00> -- 2.7V, <01> -- 2.9V, <10> -- 3.1V, <11> -- 3.3V */
	pm860x_set_bits(info->i2c, PM8607_MEAS_EN2, MEAS2_VRTC, MEAS2_VRTC);

	/* calibrate VRTC */
	INIT_DELAYED_WORK(&info->calib_work, calibrate_vrtc_work);
	schedule_delayed_work(&info->calib_work, VRTC_CALIB_INTERVAL);
	#endif /* VRTC_CALIBRATION */

	device_init_wakeup(&pdev->dev, 1);

	return 0;
	}

	static int pm860x_rtc_remove(struct platform_device *pdev)
	{
	struct pm860x_rtc_info *info = platform_get_drvdata(pdev);

	#ifdef VRTC_CALIBRATION
	cancel_delayed_work_sync(&info->calib_work);
	/* disable measurement */
	pm860x_set_bits(info->i2c, PM8607_MEAS_EN2, MEAS2_VRTC, 0);
	#endif /* VRTC_CALIBRATION */

	return 0;
	}

	#ifdef CONFIG_PM_SLEEP
	static int pm860x_rtc_suspend(struct device *dev)
	{
	struct platform_device *pdev = to_platform_device(dev);
	struct pm860x_chip *chip = dev_get_drvdata(pdev->dev.parent);

	if (device_may_wakeup(dev))
	chip->wakeup_flag \|= 1 << PM8607_IRQ_RTC;
	return 0;
	}
	static int pm860x_rtc_resume(struct device *dev)
	{
	struct platform_device *pdev = to_platform_device(dev);
	struct pm860x_chip *chip = dev_get_drvdata(pdev->dev.parent);

	if (device_may_wakeup(dev))
	chip->wakeup_flag &= ~(1 << PM8607_IRQ_RTC);
	return 0;
	}
	#endif

	static SIMPLE_DEV_PM_OPS(pm860x_rtc_pm_ops, pm860x_rtc_suspend, pm860x_rtc_resume);

	static struct platform_driver pm860x_rtc_driver = {
	.driver = {
	.name = "88pm860x-rtc",
	.pm = &pm860x_rtc_pm_ops,
	},
	.probe = pm860x_rtc_probe,
	.remove = pm860x_rtc_remove,
	};

	module_platform_driver(pm860x_rtc_driver);

	MODULE_DESCRIPTION("Marvell 88PM860x RTC driver");
	MODULE_AUTHOR("Haojian Zhuang <haojian.zhuang@marvell.com>");
	MODULE_LICENSE("GPL");