drivers/rtc/rtc-rv3028.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * RTC driver for the Micro Crystal RV3028
  *
  * Copyright (C) 2019 Micro Crystal SA
  *
  * Alexandre Belloni <alexandre.belloni@bootlin.com>
  *
  */

 #include <linux/bcd.h>
 #include <linux/bitops.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/log2.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/regmap.h>
 #include <linux/rtc.h>

 #define RV3028_SEC			0x00
 #define RV3028_MIN			0x01
 #define RV3028_HOUR			0x02
 #define RV3028_WDAY			0x03
 #define RV3028_DAY			0x04
 #define RV3028_MONTH			0x05
 #define RV3028_YEAR			0x06
 #define RV3028_ALARM_MIN		0x07
 #define RV3028_ALARM_HOUR		0x08
 #define RV3028_ALARM_DAY		0x09
 #define RV3028_STATUS			0x0E
 #define RV3028_CTRL1			0x0F
 #define RV3028_CTRL2			0x10
 #define RV3028_EVT_CTRL			0x13
 #define RV3028_TS_COUNT			0x14
 #define RV3028_TS_SEC			0x15
 #define RV3028_RAM1			0x1F
 #define RV3028_EEPROM_ADDR		0x25
 #define RV3028_EEPROM_DATA		0x26
 #define RV3028_EEPROM_CMD		0x27
 #define RV3028_CLKOUT			0x35
 #define RV3028_OFFSET			0x36
 #define RV3028_BACKUP			0x37

 #define RV3028_STATUS_PORF		BIT(0)
 #define RV3028_STATUS_EVF		BIT(1)
 #define RV3028_STATUS_AF		BIT(2)
 #define RV3028_STATUS_TF		BIT(3)
 #define RV3028_STATUS_UF		BIT(4)
 #define RV3028_STATUS_BSF		BIT(5)
 #define RV3028_STATUS_CLKF		BIT(6)
 #define RV3028_STATUS_EEBUSY		BIT(7)

 #define RV3028_CTRL1_EERD		BIT(3)
 #define RV3028_CTRL1_WADA		BIT(5)

 #define RV3028_CTRL2_RESET		BIT(0)
 #define RV3028_CTRL2_12_24		BIT(1)
 #define RV3028_CTRL2_EIE		BIT(2)
 #define RV3028_CTRL2_AIE		BIT(3)
 #define RV3028_CTRL2_TIE		BIT(4)
 #define RV3028_CTRL2_UIE		BIT(5)
 #define RV3028_CTRL2_TSE		BIT(7)

 #define RV3028_EVT_CTRL_TSR		BIT(2)

 #define RV3028_EEPROM_CMD_WRITE		0x21
 #define RV3028_EEPROM_CMD_READ		0x22

 #define RV3028_EEBUSY_POLL		10000
 #define RV3028_EEBUSY_TIMEOUT		100000

 #define RV3028_BACKUP_TCE		BIT(5)
 #define RV3028_BACKUP_TCR_MASK		GENMASK(1,0)

 #define OFFSET_STEP_PPT			953674

 enum rv3028_type {
 	rv_3028,
 };

 struct rv3028_data {
 	struct regmap *regmap;
 	struct rtc_device *rtc;
 	enum rv3028_type type;
 };

 static u16 rv3028_trickle_resistors[] = {1000, 3000, 6000, 11000};

 static ssize_t timestamp0_store(struct device *dev,
 				struct device_attribute *attr,
 				const char *buf, size_t count)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);

 	regmap_update_bits(rv3028->regmap, RV3028_EVT_CTRL, RV3028_EVT_CTRL_TSR,
 			   RV3028_EVT_CTRL_TSR);

 	return count;
 };

 static ssize_t timestamp0_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);
 	struct rtc_time tm;
 	int ret, count;
 	u8 date[6];

 	ret = regmap_read(rv3028->regmap, RV3028_TS_COUNT, &count);
 	if (ret)
 		return ret;

 	if (!count)
 		return 0;

 	ret = regmap_bulk_read(rv3028->regmap, RV3028_TS_SEC, date,
 			       sizeof(date));
 	if (ret)
 		return ret;

 	tm.tm_sec = bcd2bin(date[0]);
 	tm.tm_min = bcd2bin(date[1]);
 	tm.tm_hour = bcd2bin(date[2]);
 	tm.tm_mday = bcd2bin(date[3]);
 	tm.tm_mon = bcd2bin(date[4]) - 1;
 	tm.tm_year = bcd2bin(date[5]) + 100;

 	ret = rtc_valid_tm(&tm);
 	if (ret)
 		return ret;

 	return sprintf(buf, "%llu\n",
 		       (unsigned long long)rtc_tm_to_time64(&tm));
 };

 static DEVICE_ATTR_RW(timestamp0);

 static ssize_t timestamp0_count_show(struct device *dev,
 				     struct device_attribute *attr, char *buf)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);
 	int ret, count;

 	ret = regmap_read(rv3028->regmap, RV3028_TS_COUNT, &count);
 	if (ret)
 		return ret;

 	return sprintf(buf, "%u\n", count);
 };

 static DEVICE_ATTR_RO(timestamp0_count);

 static struct attribute *rv3028_attrs[] = {
 	&dev_attr_timestamp0.attr,
 	&dev_attr_timestamp0_count.attr,
 	NULL
 };

 static const struct attribute_group rv3028_attr_group = {
 	.attrs	= rv3028_attrs,
 };

 static irqreturn_t rv3028_handle_irq(int irq, void *dev_id)
 {
 	struct rv3028_data *rv3028 = dev_id;
 	unsigned long events = 0;
 	u32 status = 0, ctrl = 0;

 	if (regmap_read(rv3028->regmap, RV3028_STATUS, &status) < 0 ||
 	   status == 0) {
 		return IRQ_NONE;
 	}

 	if (status & RV3028_STATUS_PORF)
 		dev_warn(&rv3028->rtc->dev, "Voltage low, data loss detected.\n");

 	if (status & RV3028_STATUS_TF) {
 		status |= RV3028_STATUS_TF;
 		ctrl |= RV3028_CTRL2_TIE;
 		events |= RTC_PF;
 	}

 	if (status & RV3028_STATUS_AF) {
 		status |= RV3028_STATUS_AF;
 		ctrl |= RV3028_CTRL2_AIE;
 		events |= RTC_AF;
 	}

 	if (status & RV3028_STATUS_UF) {
 		status |= RV3028_STATUS_UF;
 		ctrl |= RV3028_CTRL2_UIE;
 		events |= RTC_UF;
 	}

 	if (events) {
 		rtc_update_irq(rv3028->rtc, 1, events);
 		regmap_update_bits(rv3028->regmap, RV3028_STATUS, status, 0);
 		regmap_update_bits(rv3028->regmap, RV3028_CTRL2, ctrl, 0);
 	}

 	if (status & RV3028_STATUS_EVF) {
 		sysfs_notify(&rv3028->rtc->dev.kobj, NULL,
 			     dev_attr_timestamp0.attr.name);
 		dev_warn(&rv3028->rtc->dev, "event detected");
 	}

 	return IRQ_HANDLED;
 }

 static int rv3028_get_time(struct device *dev, struct rtc_time *tm)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
 	u8 date[7];
 	int ret, status;

 	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
 	if (ret < 0)
 		return ret;

 	if (status & RV3028_STATUS_PORF) {
 		dev_warn(dev, "Voltage low, data is invalid.\n");
 		return -EINVAL;
 	}

 	ret = regmap_bulk_read(rv3028->regmap, RV3028_SEC, date, sizeof(date));
 	if (ret)
 		return ret;

 	tm->tm_sec  = bcd2bin(date[RV3028_SEC] & 0x7f);
 	tm->tm_min  = bcd2bin(date[RV3028_MIN] & 0x7f);
 	tm->tm_hour = bcd2bin(date[RV3028_HOUR] & 0x3f);
 	tm->tm_wday = ilog2(date[RV3028_WDAY] & 0x7f);
 	tm->tm_mday = bcd2bin(date[RV3028_DAY] & 0x3f);
 	tm->tm_mon  = bcd2bin(date[RV3028_MONTH] & 0x1f) - 1;
 	tm->tm_year = bcd2bin(date[RV3028_YEAR]) + 100;

 	return 0;
 }

 static int rv3028_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
 	u8 date[7];
 	int ret;

 	date[RV3028_SEC]   = bin2bcd(tm->tm_sec);
 	date[RV3028_MIN]   = bin2bcd(tm->tm_min);
 	date[RV3028_HOUR]  = bin2bcd(tm->tm_hour);
 	date[RV3028_WDAY]  = 1 << (tm->tm_wday);
 	date[RV3028_DAY]   = bin2bcd(tm->tm_mday);
 	date[RV3028_MONTH] = bin2bcd(tm->tm_mon + 1);
 	date[RV3028_YEAR]  = bin2bcd(tm->tm_year - 100);

 	/*
 	 * Writing to the Seconds register has the same effect as setting RESET
 	 * bit to 1
 	 */
 	ret = regmap_bulk_write(rv3028->regmap, RV3028_SEC, date,
 				sizeof(date));
 	if (ret)
 		return ret;

 	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
 				 RV3028_STATUS_PORF, 0);

 	return ret;
 }

 static int rv3028_get_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
 	u8 alarmvals[3];
 	int status, ctrl, ret;

 	ret = regmap_bulk_read(rv3028->regmap, RV3028_ALARM_MIN, alarmvals,
 			       sizeof(alarmvals));
 	if (ret)
 		return ret;

 	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
 	if (ret < 0)
 		return ret;

 	ret = regmap_read(rv3028->regmap, RV3028_CTRL2, &ctrl);
 	if (ret < 0)
 		return ret;

 	alrm->time.tm_sec  = 0;
 	alrm->time.tm_min  = bcd2bin(alarmvals[0] & 0x7f);
 	alrm->time.tm_hour = bcd2bin(alarmvals[1] & 0x3f);
 	alrm->time.tm_mday = bcd2bin(alarmvals[2] & 0x3f);

 	alrm->enabled = !!(ctrl & RV3028_CTRL2_AIE);
 	alrm->pending = (status & RV3028_STATUS_AF) && alrm->enabled;

 	return 0;
 }

 static int rv3028_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
 	u8 alarmvals[3];
 	u8 ctrl = 0;
 	int ret;

 	/* The alarm has no seconds, round up to nearest minute */
 	if (alrm->time.tm_sec) {
 		time64_t alarm_time = rtc_tm_to_time64(&alrm->time);

 		alarm_time += 60 - alrm->time.tm_sec;
 		rtc_time64_to_tm(alarm_time, &alrm->time);
 	}

 	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
 				 RV3028_CTRL2_AIE | RV3028_CTRL2_UIE, 0);
 	if (ret)
 		return ret;

 	alarmvals[0] = bin2bcd(alrm->time.tm_min);
 	alarmvals[1] = bin2bcd(alrm->time.tm_hour);
 	alarmvals[2] = bin2bcd(alrm->time.tm_mday);

 	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
 				 RV3028_STATUS_AF, 0);
 	if (ret)
 		return ret;

 	ret = regmap_bulk_write(rv3028->regmap, RV3028_ALARM_MIN, alarmvals,
 				sizeof(alarmvals));
 	if (ret)
 		return ret;

 	if (alrm->enabled) {
 		if (rv3028->rtc->uie_rtctimer.enabled)
 			ctrl |= RV3028_CTRL2_UIE;
 		if (rv3028->rtc->aie_timer.enabled)
 			ctrl |= RV3028_CTRL2_AIE;
 	}

 	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
 				 RV3028_CTRL2_UIE | RV3028_CTRL2_AIE, ctrl);

 	return ret;
 }

 static int rv3028_alarm_irq_enable(struct device *dev, unsigned int enabled)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
 	int ctrl = 0, ret;

 	if (enabled) {
 		if (rv3028->rtc->uie_rtctimer.enabled)
 			ctrl |= RV3028_CTRL2_UIE;
 		if (rv3028->rtc->aie_timer.enabled)
 			ctrl |= RV3028_CTRL2_AIE;
 	}

 	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
 				 RV3028_STATUS_AF | RV3028_STATUS_UF, 0);
 	if (ret)
 		return ret;

 	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
 				 RV3028_CTRL2_UIE | RV3028_CTRL2_AIE, ctrl);
 	if (ret)
 		return ret;

 	return 0;
 }

 static int rv3028_read_offset(struct device *dev, long *offset)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
 	int ret, value, steps;

 	ret = regmap_read(rv3028->regmap, RV3028_OFFSET, &value);
 	if (ret < 0)
 		return ret;

 	steps = sign_extend32(value << 1, 8);

 	ret = regmap_read(rv3028->regmap, RV3028_BACKUP, &value);
 	if (ret < 0)
 		return ret;

 	steps += value >> 7;

 	*offset = DIV_ROUND_CLOSEST(steps * OFFSET_STEP_PPT, 1000);

 	return 0;
 }

 static int rv3028_set_offset(struct device *dev, long offset)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
 	int ret;

 	offset = clamp(offset, -244141L, 243187L) * 1000;
 	offset = DIV_ROUND_CLOSEST(offset, OFFSET_STEP_PPT);

 	ret = regmap_write(rv3028->regmap, RV3028_OFFSET, offset >> 1);
 	if (ret < 0)
 		return ret;

 	return regmap_update_bits(rv3028->regmap, RV3028_BACKUP, BIT(7),
 				  offset << 7);
 }

 static int rv3028_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 {
 	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
 	int status, ret = 0;

 	switch (cmd) {
 	case RTC_VL_READ:
 		ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
 		if (ret < 0)
 			return ret;

 		if (status & RV3028_STATUS_PORF)
 			dev_warn(&rv3028->rtc->dev, "Voltage low, data loss detected.\n");

 		status &= RV3028_STATUS_PORF;

 		if (copy_to_user((void __user *)arg, &status, sizeof(int)))
 			return -EFAULT;

 		return 0;

 	case RTC_VL_CLR:
 		ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
 					 RV3028_STATUS_PORF, 0);

 		return ret;

 	default:
 		return -ENOIOCTLCMD;
 	}
 }

 static int rv3028_nvram_write(void *priv, unsigned int offset, void *val,
 			      size_t bytes)
 {
 	return regmap_bulk_write(priv, RV3028_RAM1 + offset, val, bytes);
 }

 static int rv3028_nvram_read(void *priv, unsigned int offset, void *val,
 			     size_t bytes)
 {
 	return regmap_bulk_read(priv, RV3028_RAM1 + offset, val, bytes);
 }

 static int rv3028_eeprom_write(void *priv, unsigned int offset, void *val,
 			       size_t bytes)
 {
 	u32 status, ctrl1;
 	int i, ret, err;
 	u8 *buf = val;

 	ret = regmap_read(priv, RV3028_CTRL1, &ctrl1);
 	if (ret)
 		return ret;

 	if (!(ctrl1 & RV3028_CTRL1_EERD)) {
 		ret = regmap_update_bits(priv, RV3028_CTRL1,
 					 RV3028_CTRL1_EERD, RV3028_CTRL1_EERD);
 		if (ret)
 			return ret;

 		ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
 					       !(status & RV3028_STATUS_EEBUSY),
 					       RV3028_EEBUSY_POLL,
 					       RV3028_EEBUSY_TIMEOUT);
 		if (ret)
 			goto restore_eerd;
 	}

 	for (i = 0; i < bytes; i++) {
 		ret = regmap_write(priv, RV3028_EEPROM_ADDR, offset + i);
 		if (ret)
 			goto restore_eerd;

 		ret = regmap_write(priv, RV3028_EEPROM_DATA, buf[i]);
 		if (ret)
 			goto restore_eerd;

 		ret = regmap_write(priv, RV3028_EEPROM_CMD, 0x0);
 		if (ret)
 			goto restore_eerd;

 		ret = regmap_write(priv, RV3028_EEPROM_CMD,
 				   RV3028_EEPROM_CMD_WRITE);
 		if (ret)
 			goto restore_eerd;

 		usleep_range(RV3028_EEBUSY_POLL, RV3028_EEBUSY_TIMEOUT);

 		ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
 					       !(status & RV3028_STATUS_EEBUSY),
 					       RV3028_EEBUSY_POLL,
 					       RV3028_EEBUSY_TIMEOUT);
 		if (ret)
 			goto restore_eerd;
 	}

 restore_eerd:
 	if (!(ctrl1 & RV3028_CTRL1_EERD))
 	{
 		err = regmap_update_bits(priv, RV3028_CTRL1, RV3028_CTRL1_EERD,
 					 0);
 		if (err && !ret)
 			ret = err;
 	}

 	return ret;
 }

 static int rv3028_eeprom_read(void *priv, unsigned int offset, void *val,
 			      size_t bytes)
 {
 	u32 status, ctrl1, data;
 	int i, ret, err;
 	u8 *buf = val;

 	ret = regmap_read(priv, RV3028_CTRL1, &ctrl1);
 	if (ret)
 		return ret;

 	if (!(ctrl1 & RV3028_CTRL1_EERD)) {
 		ret = regmap_update_bits(priv, RV3028_CTRL1,
 					 RV3028_CTRL1_EERD, RV3028_CTRL1_EERD);
 		if (ret)
 			return ret;

 		ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
 					       !(status & RV3028_STATUS_EEBUSY),
 					       RV3028_EEBUSY_POLL,
 					       RV3028_EEBUSY_TIMEOUT);
 		if (ret)
 			goto restore_eerd;
 	}

 	for (i = 0; i < bytes; i++) {
 		ret = regmap_write(priv, RV3028_EEPROM_ADDR, offset + i);
 		if (ret)
 			goto restore_eerd;

 		ret = regmap_write(priv, RV3028_EEPROM_CMD, 0x0);
 		if (ret)
 			goto restore_eerd;

 		ret = regmap_write(priv, RV3028_EEPROM_CMD,
 				   RV3028_EEPROM_CMD_READ);
 		if (ret)
 			goto restore_eerd;

 		ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
 					       !(status & RV3028_STATUS_EEBUSY),
 					       RV3028_EEBUSY_POLL,
 					       RV3028_EEBUSY_TIMEOUT);
 		if (ret)
 			goto restore_eerd;

 		ret = regmap_read(priv, RV3028_EEPROM_DATA, &data);
 		if (ret)
 			goto restore_eerd;
 		buf[i] = data;
 	}

 restore_eerd:
 	if (!(ctrl1 & RV3028_CTRL1_EERD))
 	{
 		err = regmap_update_bits(priv, RV3028_CTRL1, RV3028_CTRL1_EERD,
 					 0);
 		if (err && !ret)
 			ret = err;
 	}

 	return ret;
 }

 static struct rtc_class_ops rv3028_rtc_ops = {
 	.read_time = rv3028_get_time,
 	.set_time = rv3028_set_time,
 	.read_offset = rv3028_read_offset,
 	.set_offset = rv3028_set_offset,
 	.ioctl = rv3028_ioctl,
 };

 static const struct regmap_config regmap_config = {
         .reg_bits = 8,
         .val_bits = 8,
         .max_register = 0x37,
 };

 static int rv3028_probe(struct i2c_client *client)
 {
 	struct rv3028_data *rv3028;
 	int ret, status;
 	u32 ohms;
 	struct nvmem_config nvmem_cfg = {
 		.name = "rv3028_nvram",
 		.word_size = 1,
 		.stride = 1,
 		.size = 2,
 		.type = NVMEM_TYPE_BATTERY_BACKED,
 		.reg_read = rv3028_nvram_read,
 		.reg_write = rv3028_nvram_write,
 	};
 	struct nvmem_config eeprom_cfg = {
 		.name = "rv3028_eeprom",
 		.word_size = 1,
 		.stride = 1,
 		.size = 43,
 		.type = NVMEM_TYPE_EEPROM,
 		.reg_read = rv3028_eeprom_read,
 		.reg_write = rv3028_eeprom_write,
 	};

 	rv3028 = devm_kzalloc(&client->dev, sizeof(struct rv3028_data),
 			      GFP_KERNEL);
 	if (!rv3028)
 		return -ENOMEM;

 	rv3028->regmap = devm_regmap_init_i2c(client, &regmap_config);
 	if (IS_ERR(rv3028->regmap))
 		return PTR_ERR(rv3028->regmap);

 	i2c_set_clientdata(client, rv3028);

 	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
 	if (ret < 0)
 		return ret;

 	if (status & RV3028_STATUS_PORF)
 		dev_warn(&client->dev, "Voltage low, data loss detected.\n");

 	if (status & RV3028_STATUS_AF)
 		dev_warn(&client->dev, "An alarm may have been missed.\n");

 	rv3028->rtc = devm_rtc_allocate_device(&client->dev);
 	if (IS_ERR(rv3028->rtc))
 		return PTR_ERR(rv3028->rtc);

 	if (client->irq > 0) {
 		ret = devm_request_threaded_irq(&client->dev, client->irq,
 						NULL, rv3028_handle_irq,
 						IRQF_TRIGGER_LOW | IRQF_ONESHOT,
 						"rv3028", rv3028);
 		if (ret) {
 			dev_warn(&client->dev, "unable to request IRQ, alarms disabled\n");
 			client->irq = 0;
 		} else {
 			rv3028_rtc_ops.read_alarm = rv3028_get_alarm;
 			rv3028_rtc_ops.set_alarm = rv3028_set_alarm;
 			rv3028_rtc_ops.alarm_irq_enable = rv3028_alarm_irq_enable;
 		}
 	}

 	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL1,
 				 RV3028_CTRL1_WADA, RV3028_CTRL1_WADA);
 	if (ret)
 		return ret;

 	/* setup timestamping */
 	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
 				 RV3028_CTRL2_EIE | RV3028_CTRL2_TSE,
 				 RV3028_CTRL2_EIE | RV3028_CTRL2_TSE);
 	if (ret)
 		return ret;

 	/* setup trickle charger */
 	if (!device_property_read_u32(&client->dev, "trickle-resistor-ohms",
 				      &ohms)) {
 		int i;

 		for (i = 0; i < ARRAY_SIZE(rv3028_trickle_resistors); i++)
 			if (ohms == rv3028_trickle_resistors[i])
 				break;

 		if (i < ARRAY_SIZE(rv3028_trickle_resistors)) {
 			ret = regmap_update_bits(rv3028->regmap, RV3028_BACKUP,
 						 RV3028_BACKUP_TCE |
 						 RV3028_BACKUP_TCR_MASK,
 						 RV3028_BACKUP_TCE | i);
 			if (ret)
 				return ret;
 		} else {
 			dev_warn(&client->dev, "invalid trickle resistor value\n");
 		}
 	}

 	ret = rtc_add_group(rv3028->rtc, &rv3028_attr_group);
 	if (ret)
 		return ret;

 	rv3028->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 	rv3028->rtc->range_max = RTC_TIMESTAMP_END_2099;
 	rv3028->rtc->ops = &rv3028_rtc_ops;
 	ret = rtc_register_device(rv3028->rtc);
 	if (ret)
 		return ret;

 	nvmem_cfg.priv = rv3028->regmap;
 	rtc_nvmem_register(rv3028->rtc, &nvmem_cfg);
 	eeprom_cfg.priv = rv3028->regmap;
 	rtc_nvmem_register(rv3028->rtc, &eeprom_cfg);

 	rv3028->rtc->max_user_freq = 1;

 	return 0;
 }

 static const struct of_device_id rv3028_of_match[] = {
 	{ .compatible = "microcrystal,rv3028", },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, rv3028_of_match);

 static struct i2c_driver rv3028_driver = {
 	.driver = {
 		.name = "rtc-rv3028",
 		.of_match_table = of_match_ptr(rv3028_of_match),
 	},
 	.probe_new	= rv3028_probe,
 };
 module_i2c_driver(rv3028_driver);

 MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@bootlin.com>");
 MODULE_DESCRIPTION("Micro Crystal RV3028 RTC driver");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* RTC driver for the Micro Crystal RV3028
	*
	* Copyright (C) 2019 Micro Crystal SA
	*
	* Alexandre Belloni <alexandre.belloni@bootlin.com>
	*
	*/

	#include <linux/bcd.h>
	#include <linux/bitops.h>
	#include <linux/i2c.h>
	#include <linux/interrupt.h>
	#include <linux/kernel.h>
	#include <linux/log2.h>
	#include <linux/module.h>
	#include <linux/of_device.h>
	#include <linux/regmap.h>
	#include <linux/rtc.h>

	#define RV3028_SEC 0x00
	#define RV3028_MIN 0x01
	#define RV3028_HOUR 0x02
	#define RV3028_WDAY 0x03
	#define RV3028_DAY 0x04
	#define RV3028_MONTH 0x05
	#define RV3028_YEAR 0x06
	#define RV3028_ALARM_MIN 0x07
	#define RV3028_ALARM_HOUR 0x08
	#define RV3028_ALARM_DAY 0x09
	#define RV3028_STATUS 0x0E
	#define RV3028_CTRL1 0x0F
	#define RV3028_CTRL2 0x10
	#define RV3028_EVT_CTRL 0x13
	#define RV3028_TS_COUNT 0x14
	#define RV3028_TS_SEC 0x15
	#define RV3028_RAM1 0x1F
	#define RV3028_EEPROM_ADDR 0x25
	#define RV3028_EEPROM_DATA 0x26
	#define RV3028_EEPROM_CMD 0x27
	#define RV3028_CLKOUT 0x35
	#define RV3028_OFFSET 0x36
	#define RV3028_BACKUP 0x37

	#define RV3028_STATUS_PORF BIT(0)
	#define RV3028_STATUS_EVF BIT(1)
	#define RV3028_STATUS_AF BIT(2)
	#define RV3028_STATUS_TF BIT(3)
	#define RV3028_STATUS_UF BIT(4)
	#define RV3028_STATUS_BSF BIT(5)
	#define RV3028_STATUS_CLKF BIT(6)
	#define RV3028_STATUS_EEBUSY BIT(7)

	#define RV3028_CTRL1_EERD BIT(3)
	#define RV3028_CTRL1_WADA BIT(5)

	#define RV3028_CTRL2_RESET BIT(0)
	#define RV3028_CTRL2_12_24 BIT(1)
	#define RV3028_CTRL2_EIE BIT(2)
	#define RV3028_CTRL2_AIE BIT(3)
	#define RV3028_CTRL2_TIE BIT(4)
	#define RV3028_CTRL2_UIE BIT(5)
	#define RV3028_CTRL2_TSE BIT(7)

	#define RV3028_EVT_CTRL_TSR BIT(2)

	#define RV3028_EEPROM_CMD_WRITE 0x21
	#define RV3028_EEPROM_CMD_READ 0x22

	#define RV3028_EEBUSY_POLL 10000
	#define RV3028_EEBUSY_TIMEOUT 100000

	#define RV3028_BACKUP_TCE BIT(5)
	#define RV3028_BACKUP_TCR_MASK GENMASK(1,0)

	#define OFFSET_STEP_PPT 953674

	enum rv3028_type {
	rv_3028,
	};

	struct rv3028_data {
	struct regmap *regmap;
	struct rtc_device *rtc;
	enum rv3028_type type;
	};

	static u16 rv3028_trickle_resistors[] = {1000, 3000, 6000, 11000};

	static ssize_t timestamp0_store(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t count)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);

	regmap_update_bits(rv3028->regmap, RV3028_EVT_CTRL, RV3028_EVT_CTRL_TSR,
	RV3028_EVT_CTRL_TSR);

	return count;
	};

	static ssize_t timestamp0_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);
	struct rtc_time tm;
	int ret, count;
	u8 date[6];

	ret = regmap_read(rv3028->regmap, RV3028_TS_COUNT, &count);
	if (ret)
	return ret;

	if (!count)
	return 0;

	ret = regmap_bulk_read(rv3028->regmap, RV3028_TS_SEC, date,
	sizeof(date));
	if (ret)
	return ret;

	tm.tm_sec = bcd2bin(date[0]);
	tm.tm_min = bcd2bin(date[1]);
	tm.tm_hour = bcd2bin(date[2]);
	tm.tm_mday = bcd2bin(date[3]);
	tm.tm_mon = bcd2bin(date[4]) - 1;
	tm.tm_year = bcd2bin(date[5]) + 100;

	ret = rtc_valid_tm(&tm);
	if (ret)
	return ret;

	return sprintf(buf, "%llu\n",
	(unsigned long long)rtc_tm_to_time64(&tm));
	};

	static DEVICE_ATTR_RW(timestamp0);

	static ssize_t timestamp0_count_show(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev->parent);
	int ret, count;

	ret = regmap_read(rv3028->regmap, RV3028_TS_COUNT, &count);
	if (ret)
	return ret;

	return sprintf(buf, "%u\n", count);
	};

	static DEVICE_ATTR_RO(timestamp0_count);

	static struct attribute *rv3028_attrs[] = {
	&dev_attr_timestamp0.attr,
	&dev_attr_timestamp0_count.attr,
	NULL
	};

	static const struct attribute_group rv3028_attr_group = {
	.attrs = rv3028_attrs,
	};

	static irqreturn_t rv3028_handle_irq(int irq, void *dev_id)
	{
	struct rv3028_data *rv3028 = dev_id;
	unsigned long events = 0;
	u32 status = 0, ctrl = 0;

	if (regmap_read(rv3028->regmap, RV3028_STATUS, &status) < 0 \|\|
	status == 0) {
	return IRQ_NONE;
	}

	if (status & RV3028_STATUS_PORF)
	dev_warn(&rv3028->rtc->dev, "Voltage low, data loss detected.\n");

	if (status & RV3028_STATUS_TF) {
	status \|= RV3028_STATUS_TF;
	ctrl \|= RV3028_CTRL2_TIE;
	events \|= RTC_PF;
	}

	if (status & RV3028_STATUS_AF) {
	status \|= RV3028_STATUS_AF;
	ctrl \|= RV3028_CTRL2_AIE;
	events \|= RTC_AF;
	}

	if (status & RV3028_STATUS_UF) {
	status \|= RV3028_STATUS_UF;
	ctrl \|= RV3028_CTRL2_UIE;
	events \|= RTC_UF;
	}

	if (events) {
	rtc_update_irq(rv3028->rtc, 1, events);
	regmap_update_bits(rv3028->regmap, RV3028_STATUS, status, 0);
	regmap_update_bits(rv3028->regmap, RV3028_CTRL2, ctrl, 0);
	}

	if (status & RV3028_STATUS_EVF) {
	sysfs_notify(&rv3028->rtc->dev.kobj, NULL,
	dev_attr_timestamp0.attr.name);
	dev_warn(&rv3028->rtc->dev, "event detected");
	}

	return IRQ_HANDLED;
	}

	static int rv3028_get_time(struct device dev, struct rtc_time tm)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
	u8 date[7];
	int ret, status;

	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
	if (ret < 0)
	return ret;

	if (status & RV3028_STATUS_PORF) {
	dev_warn(dev, "Voltage low, data is invalid.\n");
	return -EINVAL;
	}

	ret = regmap_bulk_read(rv3028->regmap, RV3028_SEC, date, sizeof(date));
	if (ret)
	return ret;

	tm->tm_sec = bcd2bin(date[RV3028_SEC] & 0x7f);
	tm->tm_min = bcd2bin(date[RV3028_MIN] & 0x7f);
	tm->tm_hour = bcd2bin(date[RV3028_HOUR] & 0x3f);
	tm->tm_wday = ilog2(date[RV3028_WDAY] & 0x7f);
	tm->tm_mday = bcd2bin(date[RV3028_DAY] & 0x3f);
	tm->tm_mon = bcd2bin(date[RV3028_MONTH] & 0x1f) - 1;
	tm->tm_year = bcd2bin(date[RV3028_YEAR]) + 100;

	return 0;
	}

	static int rv3028_set_time(struct device dev, struct rtc_time tm)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
	u8 date[7];
	int ret;

	date[RV3028_SEC] = bin2bcd(tm->tm_sec);
	date[RV3028_MIN] = bin2bcd(tm->tm_min);
	date[RV3028_HOUR] = bin2bcd(tm->tm_hour);
	date[RV3028_WDAY] = 1 << (tm->tm_wday);
	date[RV3028_DAY] = bin2bcd(tm->tm_mday);
	date[RV3028_MONTH] = bin2bcd(tm->tm_mon + 1);
	date[RV3028_YEAR] = bin2bcd(tm->tm_year - 100);

	/*
	* Writing to the Seconds register has the same effect as setting RESET
	* bit to 1
	*/
	ret = regmap_bulk_write(rv3028->regmap, RV3028_SEC, date,
	sizeof(date));
	if (ret)
	return ret;

	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
	RV3028_STATUS_PORF, 0);

	return ret;
	}

	static int rv3028_get_alarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
	u8 alarmvals[3];
	int status, ctrl, ret;

	ret = regmap_bulk_read(rv3028->regmap, RV3028_ALARM_MIN, alarmvals,
	sizeof(alarmvals));
	if (ret)
	return ret;

	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
	if (ret < 0)
	return ret;

	ret = regmap_read(rv3028->regmap, RV3028_CTRL2, &ctrl);
	if (ret < 0)
	return ret;

	alrm->time.tm_sec = 0;
	alrm->time.tm_min = bcd2bin(alarmvals[0] & 0x7f);
	alrm->time.tm_hour = bcd2bin(alarmvals[1] & 0x3f);
	alrm->time.tm_mday = bcd2bin(alarmvals[2] & 0x3f);

	alrm->enabled = !!(ctrl & RV3028_CTRL2_AIE);
	alrm->pending = (status & RV3028_STATUS_AF) && alrm->enabled;

	return 0;
	}

	static int rv3028_set_alarm(struct device dev, struct rtc_wkalrm alrm)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
	u8 alarmvals[3];
	u8 ctrl = 0;
	int ret;

	/* The alarm has no seconds, round up to nearest minute */
	if (alrm->time.tm_sec) {
	time64_t alarm_time = rtc_tm_to_time64(&alrm->time);

	alarm_time += 60 - alrm->time.tm_sec;
	rtc_time64_to_tm(alarm_time, &alrm->time);
	}

	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
	RV3028_CTRL2_AIE \| RV3028_CTRL2_UIE, 0);
	if (ret)
	return ret;

	alarmvals[0] = bin2bcd(alrm->time.tm_min);
	alarmvals[1] = bin2bcd(alrm->time.tm_hour);
	alarmvals[2] = bin2bcd(alrm->time.tm_mday);

	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
	RV3028_STATUS_AF, 0);
	if (ret)
	return ret;

	ret = regmap_bulk_write(rv3028->regmap, RV3028_ALARM_MIN, alarmvals,
	sizeof(alarmvals));
	if (ret)
	return ret;

	if (alrm->enabled) {
	if (rv3028->rtc->uie_rtctimer.enabled)
	ctrl \|= RV3028_CTRL2_UIE;
	if (rv3028->rtc->aie_timer.enabled)
	ctrl \|= RV3028_CTRL2_AIE;
	}

	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
	RV3028_CTRL2_UIE \| RV3028_CTRL2_AIE, ctrl);

	return ret;
	}

	static int rv3028_alarm_irq_enable(struct device *dev, unsigned int enabled)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
	int ctrl = 0, ret;

	if (enabled) {
	if (rv3028->rtc->uie_rtctimer.enabled)
	ctrl \|= RV3028_CTRL2_UIE;
	if (rv3028->rtc->aie_timer.enabled)
	ctrl \|= RV3028_CTRL2_AIE;
	}

	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
	RV3028_STATUS_AF \| RV3028_STATUS_UF, 0);
	if (ret)
	return ret;

	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
	RV3028_CTRL2_UIE \| RV3028_CTRL2_AIE, ctrl);
	if (ret)
	return ret;

	return 0;
	}

	static int rv3028_read_offset(struct device dev, long offset)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
	int ret, value, steps;

	ret = regmap_read(rv3028->regmap, RV3028_OFFSET, &value);
	if (ret < 0)
	return ret;

	steps = sign_extend32(value << 1, 8);

	ret = regmap_read(rv3028->regmap, RV3028_BACKUP, &value);
	if (ret < 0)
	return ret;

	steps += value >> 7;

	offset = DIV_ROUND_CLOSEST(steps OFFSET_STEP_PPT, 1000);

	return 0;
	}

	static int rv3028_set_offset(struct device *dev, long offset)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
	int ret;

	offset = clamp(offset, -244141L, 243187L) * 1000;
	offset = DIV_ROUND_CLOSEST(offset, OFFSET_STEP_PPT);

	ret = regmap_write(rv3028->regmap, RV3028_OFFSET, offset >> 1);
	if (ret < 0)
	return ret;

	return regmap_update_bits(rv3028->regmap, RV3028_BACKUP, BIT(7),
	offset << 7);
	}

	static int rv3028_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
	{
	struct rv3028_data *rv3028 = dev_get_drvdata(dev);
	int status, ret = 0;

	switch (cmd) {
	case RTC_VL_READ:
	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
	if (ret < 0)
	return ret;

	if (status & RV3028_STATUS_PORF)
	dev_warn(&rv3028->rtc->dev, "Voltage low, data loss detected.\n");

	status &= RV3028_STATUS_PORF;

	if (copy_to_user((void __user *)arg, &status, sizeof(int)))
	return -EFAULT;

	return 0;

	case RTC_VL_CLR:
	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
	RV3028_STATUS_PORF, 0);

	return ret;

	default:
	return -ENOIOCTLCMD;
	}
	}

	static int rv3028_nvram_write(void priv, unsigned int offset, void val,
	size_t bytes)
	{
	return regmap_bulk_write(priv, RV3028_RAM1 + offset, val, bytes);
	}

	static int rv3028_nvram_read(void priv, unsigned int offset, void val,
	size_t bytes)
	{
	return regmap_bulk_read(priv, RV3028_RAM1 + offset, val, bytes);
	}

	static int rv3028_eeprom_write(void priv, unsigned int offset, void val,
	size_t bytes)
	{
	u32 status, ctrl1;
	int i, ret, err;
	u8 *buf = val;

	ret = regmap_read(priv, RV3028_CTRL1, &ctrl1);
	if (ret)
	return ret;

	if (!(ctrl1 & RV3028_CTRL1_EERD)) {
	ret = regmap_update_bits(priv, RV3028_CTRL1,
	RV3028_CTRL1_EERD, RV3028_CTRL1_EERD);
	if (ret)
	return ret;

	ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
	!(status & RV3028_STATUS_EEBUSY),
	RV3028_EEBUSY_POLL,
	RV3028_EEBUSY_TIMEOUT);
	if (ret)
	goto restore_eerd;
	}

	for (i = 0; i < bytes; i++) {
	ret = regmap_write(priv, RV3028_EEPROM_ADDR, offset + i);
	if (ret)
	goto restore_eerd;

	ret = regmap_write(priv, RV3028_EEPROM_DATA, buf[i]);
	if (ret)
	goto restore_eerd;

	ret = regmap_write(priv, RV3028_EEPROM_CMD, 0x0);
	if (ret)
	goto restore_eerd;

	ret = regmap_write(priv, RV3028_EEPROM_CMD,
	RV3028_EEPROM_CMD_WRITE);
	if (ret)
	goto restore_eerd;

	usleep_range(RV3028_EEBUSY_POLL, RV3028_EEBUSY_TIMEOUT);

	ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
	!(status & RV3028_STATUS_EEBUSY),
	RV3028_EEBUSY_POLL,
	RV3028_EEBUSY_TIMEOUT);
	if (ret)
	goto restore_eerd;
	}

	restore_eerd:
	if (!(ctrl1 & RV3028_CTRL1_EERD))
	{
	err = regmap_update_bits(priv, RV3028_CTRL1, RV3028_CTRL1_EERD,
	0);
	if (err && !ret)
	ret = err;
	}

	return ret;
	}

	static int rv3028_eeprom_read(void priv, unsigned int offset, void val,
	size_t bytes)
	{
	u32 status, ctrl1, data;
	int i, ret, err;
	u8 *buf = val;

	ret = regmap_read(priv, RV3028_CTRL1, &ctrl1);
	if (ret)
	return ret;

	if (!(ctrl1 & RV3028_CTRL1_EERD)) {
	ret = regmap_update_bits(priv, RV3028_CTRL1,
	RV3028_CTRL1_EERD, RV3028_CTRL1_EERD);
	if (ret)
	return ret;

	ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
	!(status & RV3028_STATUS_EEBUSY),
	RV3028_EEBUSY_POLL,
	RV3028_EEBUSY_TIMEOUT);
	if (ret)
	goto restore_eerd;
	}

	for (i = 0; i < bytes; i++) {
	ret = regmap_write(priv, RV3028_EEPROM_ADDR, offset + i);
	if (ret)
	goto restore_eerd;

	ret = regmap_write(priv, RV3028_EEPROM_CMD, 0x0);
	if (ret)
	goto restore_eerd;

	ret = regmap_write(priv, RV3028_EEPROM_CMD,
	RV3028_EEPROM_CMD_READ);
	if (ret)
	goto restore_eerd;

	ret = regmap_read_poll_timeout(priv, RV3028_STATUS, status,
	!(status & RV3028_STATUS_EEBUSY),
	RV3028_EEBUSY_POLL,
	RV3028_EEBUSY_TIMEOUT);
	if (ret)
	goto restore_eerd;

	ret = regmap_read(priv, RV3028_EEPROM_DATA, &data);
	if (ret)
	goto restore_eerd;
	buf[i] = data;
	}

	restore_eerd:
	if (!(ctrl1 & RV3028_CTRL1_EERD))
	{
	err = regmap_update_bits(priv, RV3028_CTRL1, RV3028_CTRL1_EERD,
	0);
	if (err && !ret)
	ret = err;
	}

	return ret;
	}

	static struct rtc_class_ops rv3028_rtc_ops = {
	.read_time = rv3028_get_time,
	.set_time = rv3028_set_time,
	.read_offset = rv3028_read_offset,
	.set_offset = rv3028_set_offset,
	.ioctl = rv3028_ioctl,
	};

	static const struct regmap_config regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,
	.max_register = 0x37,
	};

	static int rv3028_probe(struct i2c_client *client)
	{
	struct rv3028_data *rv3028;
	int ret, status;
	u32 ohms;
	struct nvmem_config nvmem_cfg = {
	.name = "rv3028_nvram",
	.word_size = 1,
	.stride = 1,
	.size = 2,
	.type = NVMEM_TYPE_BATTERY_BACKED,
	.reg_read = rv3028_nvram_read,
	.reg_write = rv3028_nvram_write,
	};
	struct nvmem_config eeprom_cfg = {
	.name = "rv3028_eeprom",
	.word_size = 1,
	.stride = 1,
	.size = 43,
	.type = NVMEM_TYPE_EEPROM,
	.reg_read = rv3028_eeprom_read,
	.reg_write = rv3028_eeprom_write,
	};

	rv3028 = devm_kzalloc(&client->dev, sizeof(struct rv3028_data),
	GFP_KERNEL);
	if (!rv3028)
	return -ENOMEM;

	rv3028->regmap = devm_regmap_init_i2c(client, &regmap_config);
	if (IS_ERR(rv3028->regmap))
	return PTR_ERR(rv3028->regmap);

	i2c_set_clientdata(client, rv3028);

	ret = regmap_read(rv3028->regmap, RV3028_STATUS, &status);
	if (ret < 0)
	return ret;

	if (status & RV3028_STATUS_PORF)
	dev_warn(&client->dev, "Voltage low, data loss detected.\n");

	if (status & RV3028_STATUS_AF)
	dev_warn(&client->dev, "An alarm may have been missed.\n");

	rv3028->rtc = devm_rtc_allocate_device(&client->dev);
	if (IS_ERR(rv3028->rtc))
	return PTR_ERR(rv3028->rtc);

	if (client->irq > 0) {
	ret = devm_request_threaded_irq(&client->dev, client->irq,
	NULL, rv3028_handle_irq,
	IRQF_TRIGGER_LOW \| IRQF_ONESHOT,
	"rv3028", rv3028);
	if (ret) {
	dev_warn(&client->dev, "unable to request IRQ, alarms disabled\n");
	client->irq = 0;
	} else {
	rv3028_rtc_ops.read_alarm = rv3028_get_alarm;
	rv3028_rtc_ops.set_alarm = rv3028_set_alarm;
	rv3028_rtc_ops.alarm_irq_enable = rv3028_alarm_irq_enable;
	}
	}

	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL1,
	RV3028_CTRL1_WADA, RV3028_CTRL1_WADA);
	if (ret)
	return ret;

	/* setup timestamping */
	ret = regmap_update_bits(rv3028->regmap, RV3028_CTRL2,
	RV3028_CTRL2_EIE \| RV3028_CTRL2_TSE,
	RV3028_CTRL2_EIE \| RV3028_CTRL2_TSE);
	if (ret)
	return ret;

	/* setup trickle charger */
	if (!device_property_read_u32(&client->dev, "trickle-resistor-ohms",
	&ohms)) {
	int i;

	for (i = 0; i < ARRAY_SIZE(rv3028_trickle_resistors); i++)
	if (ohms == rv3028_trickle_resistors[i])
	break;

	if (i < ARRAY_SIZE(rv3028_trickle_resistors)) {
	ret = regmap_update_bits(rv3028->regmap, RV3028_BACKUP,
	RV3028_BACKUP_TCE \|
	RV3028_BACKUP_TCR_MASK,
	RV3028_BACKUP_TCE \| i);
	if (ret)
	return ret;
	} else {
	dev_warn(&client->dev, "invalid trickle resistor value\n");
	}
	}

	ret = rtc_add_group(rv3028->rtc, &rv3028_attr_group);
	if (ret)
	return ret;

	rv3028->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
	rv3028->rtc->range_max = RTC_TIMESTAMP_END_2099;
	rv3028->rtc->ops = &rv3028_rtc_ops;
	ret = rtc_register_device(rv3028->rtc);
	if (ret)
	return ret;

	nvmem_cfg.priv = rv3028->regmap;
	rtc_nvmem_register(rv3028->rtc, &nvmem_cfg);
	eeprom_cfg.priv = rv3028->regmap;
	rtc_nvmem_register(rv3028->rtc, &eeprom_cfg);

	rv3028->rtc->max_user_freq = 1;

	return 0;
	}

	static const struct of_device_id rv3028_of_match[] = {
	{ .compatible = "microcrystal,rv3028", },
	{ }
	};
	MODULE_DEVICE_TABLE(of, rv3028_of_match);

	static struct i2c_driver rv3028_driver = {
	.driver = {
	.name = "rtc-rv3028",
	.of_match_table = of_match_ptr(rv3028_of_match),
	},
	.probe_new = rv3028_probe,
	};
	module_i2c_driver(rv3028_driver);

	MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@bootlin.com>");
	MODULE_DESCRIPTION("Micro Crystal RV3028 RTC driver");
	MODULE_LICENSE("GPL v2");