xref: /openbmc/linux/drivers/rtc/rtc-pcf2127.c (revision 2843d565)

// SPDX-License-Identifier: GPL-2.0-only
/*
 * An I2C and SPI driver for the NXP PCF2127/29 RTC
 * Copyright 2013 Til-Technologies
 *
 * Author: Renaud Cerrato <r.cerrato@til-technologies.fr>
 *
 * Watchdog and tamper functions
 * Author: Bruno Thomsen <bruno.thomsen@gmail.com>
 *
 * based on the other drivers in this same directory.
 *
 * Datasheet: http://cache.nxp.com/documents/data_sheet/PCF2127.pdf
 */

#include <linux/i2c.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/regmap.h>
#include <linux/watchdog.h>

/* Control register 1 */
#define PCF2127_REG_CTRL1		0x00
#define PCF2127_BIT_CTRL1_POR_OVRD		BIT(3)
#define PCF2127_BIT_CTRL1_TSF1			BIT(4)
/* Control register 2 */
#define PCF2127_REG_CTRL2		0x01
#define PCF2127_BIT_CTRL2_AIE			BIT(1)
#define PCF2127_BIT_CTRL2_TSIE			BIT(2)
#define PCF2127_BIT_CTRL2_AF			BIT(4)
#define PCF2127_BIT_CTRL2_TSF2			BIT(5)
#define PCF2127_BIT_CTRL2_WDTF			BIT(6)
/* Control register 3 */
#define PCF2127_REG_CTRL3		0x02
#define PCF2127_BIT_CTRL3_BLIE			BIT(0)
#define PCF2127_BIT_CTRL3_BIE			BIT(1)
#define PCF2127_BIT_CTRL3_BLF			BIT(2)
#define PCF2127_BIT_CTRL3_BF			BIT(3)
#define PCF2127_BIT_CTRL3_BTSE			BIT(4)
/* Time and date registers */
#define PCF2127_REG_SC			0x03
#define PCF2127_BIT_SC_OSF			BIT(7)
#define PCF2127_REG_MN			0x04
#define PCF2127_REG_HR			0x05
#define PCF2127_REG_DM			0x06
#define PCF2127_REG_DW			0x07
#define PCF2127_REG_MO			0x08
#define PCF2127_REG_YR			0x09
/* Alarm registers */
#define PCF2127_REG_ALARM_SC		0x0A
#define PCF2127_REG_ALARM_MN		0x0B
#define PCF2127_REG_ALARM_HR		0x0C
#define PCF2127_REG_ALARM_DM		0x0D
#define PCF2127_REG_ALARM_DW		0x0E
#define PCF2127_BIT_ALARM_AE			BIT(7)
/* CLKOUT control register */
#define PCF2127_REG_CLKOUT		0x0f
#define PCF2127_BIT_CLKOUT_OTPR			BIT(5)
/* Watchdog registers */
#define PCF2127_REG_WD_CTL		0x10
#define PCF2127_BIT_WD_CTL_TF0			BIT(0)
#define PCF2127_BIT_WD_CTL_TF1			BIT(1)
#define PCF2127_BIT_WD_CTL_CD0			BIT(6)
#define PCF2127_BIT_WD_CTL_CD1			BIT(7)
#define PCF2127_REG_WD_VAL		0x11
/* Tamper timestamp registers */
#define PCF2127_REG_TS_CTRL		0x12
#define PCF2127_BIT_TS_CTRL_TSOFF		BIT(6)
#define PCF2127_BIT_TS_CTRL_TSM			BIT(7)
#define PCF2127_REG_TS_SC		0x13
#define PCF2127_REG_TS_MN		0x14
#define PCF2127_REG_TS_HR		0x15
#define PCF2127_REG_TS_DM		0x16
#define PCF2127_REG_TS_MO		0x17
#define PCF2127_REG_TS_YR		0x18
/*
 * RAM registers
 * PCF2127 has 512 bytes general-purpose static RAM (SRAM) that is
 * battery backed and can survive a power outage.
 * PCF2129 doesn't have this feature.
 */
#define PCF2127_REG_RAM_ADDR_MSB	0x1A
#define PCF2127_REG_RAM_WRT_CMD		0x1C
#define PCF2127_REG_RAM_RD_CMD		0x1D

/* Watchdog timer value constants */
#define PCF2127_WD_VAL_STOP		0
#define PCF2127_WD_VAL_MIN		2
#define PCF2127_WD_VAL_MAX		255
#define PCF2127_WD_VAL_DEFAULT		60

struct pcf2127 {
	struct rtc_device *rtc;
	struct watchdog_device wdd;
	struct regmap *regmap;
};

/*
 * In the routines that deal directly with the pcf2127 hardware, we use
 * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
 */
static int pcf2127_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
	unsigned char buf[10];
	int ret;

	/*
	 * Avoid reading CTRL2 register as it causes WD_VAL register
	 * value to reset to 0 which means watchdog is stopped.
	 */
	ret = regmap_bulk_read(pcf2127->regmap, PCF2127_REG_CTRL3,
			       (buf + PCF2127_REG_CTRL3),
			       ARRAY_SIZE(buf) - PCF2127_REG_CTRL3);
	if (ret) {
		dev_err(dev, "%s: read error\n", __func__);
		return ret;
	}

	if (buf[PCF2127_REG_CTRL3] & PCF2127_BIT_CTRL3_BLF)
		dev_info(dev,
			"low voltage detected, check/replace RTC battery.\n");

	/* Clock integrity is not guaranteed when OSF flag is set. */
	if (buf[PCF2127_REG_SC] & PCF2127_BIT_SC_OSF) {
		/*
		 * no need clear the flag here,
		 * it will be cleared once the new date is saved
		 */
		dev_warn(dev,
			 "oscillator stop detected, date/time is not reliable\n");
		return -EINVAL;
	}

	dev_dbg(dev,
		"%s: raw data is cr3=%02x, sec=%02x, min=%02x, hr=%02x, "
		"mday=%02x, wday=%02x, mon=%02x, year=%02x\n",
		__func__, buf[PCF2127_REG_CTRL3], buf[PCF2127_REG_SC],
		buf[PCF2127_REG_MN], buf[PCF2127_REG_HR],
		buf[PCF2127_REG_DM], buf[PCF2127_REG_DW],
		buf[PCF2127_REG_MO], buf[PCF2127_REG_YR]);

	tm->tm_sec = bcd2bin(buf[PCF2127_REG_SC] & 0x7F);
	tm->tm_min = bcd2bin(buf[PCF2127_REG_MN] & 0x7F);
	tm->tm_hour = bcd2bin(buf[PCF2127_REG_HR] & 0x3F); /* rtc hr 0-23 */
	tm->tm_mday = bcd2bin(buf[PCF2127_REG_DM] & 0x3F);
	tm->tm_wday = buf[PCF2127_REG_DW] & 0x07;
	tm->tm_mon = bcd2bin(buf[PCF2127_REG_MO] & 0x1F) - 1; /* rtc mn 1-12 */
	tm->tm_year = bcd2bin(buf[PCF2127_REG_YR]);
	tm->tm_year += 100;

	dev_dbg(dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
		"mday=%d, mon=%d, year=%d, wday=%d\n",
		__func__,
		tm->tm_sec, tm->tm_min, tm->tm_hour,
		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);

	return 0;
}

static int pcf2127_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
	unsigned char buf[7];
	int i = 0, err;

	dev_dbg(dev, "%s: secs=%d, mins=%d, hours=%d, "
		"mday=%d, mon=%d, year=%d, wday=%d\n",
		__func__,
		tm->tm_sec, tm->tm_min, tm->tm_hour,
		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);

	/* hours, minutes and seconds */
	buf[i++] = bin2bcd(tm->tm_sec);	/* this will also clear OSF flag */
	buf[i++] = bin2bcd(tm->tm_min);
	buf[i++] = bin2bcd(tm->tm_hour);
	buf[i++] = bin2bcd(tm->tm_mday);
	buf[i++] = tm->tm_wday & 0x07;

	/* month, 1 - 12 */
	buf[i++] = bin2bcd(tm->tm_mon + 1);

	/* year */
	buf[i++] = bin2bcd(tm->tm_year - 100);

	/* write register's data */
	err = regmap_bulk_write(pcf2127->regmap, PCF2127_REG_SC, buf, i);
	if (err) {
		dev_err(dev,
			"%s: err=%d", __func__, err);
		return err;
	}

	return 0;
}

static int pcf2127_rtc_ioctl(struct device *dev,
				unsigned int cmd, unsigned long arg)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
	int val, touser = 0;
	int ret;

	switch (cmd) {
	case RTC_VL_READ:
		ret = regmap_read(pcf2127->regmap, PCF2127_REG_CTRL3, &val);
		if (ret)
			return ret;

		if (val & PCF2127_BIT_CTRL3_BLF)
			touser |= RTC_VL_BACKUP_LOW;

		if (val & PCF2127_BIT_CTRL3_BF)
			touser |= RTC_VL_BACKUP_SWITCH;

		return put_user(touser, (unsigned int __user *)arg);

	case RTC_VL_CLR:
		return regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL3,
					  PCF2127_BIT_CTRL3_BF, 0);

	default:
		return -ENOIOCTLCMD;
	}
}

static int pcf2127_nvmem_read(void *priv, unsigned int offset,
			      void *val, size_t bytes)
{
	struct pcf2127 *pcf2127 = priv;
	int ret;
	unsigned char offsetbuf[] = { offset >> 8, offset };

	ret = regmap_bulk_write(pcf2127->regmap, PCF2127_REG_RAM_ADDR_MSB,
				offsetbuf, 2);
	if (ret)
		return ret;

	return regmap_bulk_read(pcf2127->regmap, PCF2127_REG_RAM_RD_CMD,
				val, bytes);
}

static int pcf2127_nvmem_write(void *priv, unsigned int offset,
			       void *val, size_t bytes)
{
	struct pcf2127 *pcf2127 = priv;
	int ret;
	unsigned char offsetbuf[] = { offset >> 8, offset };

	ret = regmap_bulk_write(pcf2127->regmap, PCF2127_REG_RAM_ADDR_MSB,
				offsetbuf, 2);
	if (ret)
		return ret;

	return regmap_bulk_write(pcf2127->regmap, PCF2127_REG_RAM_WRT_CMD,
				 val, bytes);
}

/* watchdog driver */

static int pcf2127_wdt_ping(struct watchdog_device *wdd)
{
	struct pcf2127 *pcf2127 = watchdog_get_drvdata(wdd);

	return regmap_write(pcf2127->regmap, PCF2127_REG_WD_VAL, wdd->timeout);
}

/*
 * Restart watchdog timer if feature is active.
 *
 * Note: Reading CTRL2 register causes watchdog to stop which is unfortunate,
 * since register also contain control/status flags for other features.
 * Always call this function after reading CTRL2 register.
 */
static int pcf2127_wdt_active_ping(struct watchdog_device *wdd)
{
	int ret = 0;

	if (watchdog_active(wdd)) {
		ret = pcf2127_wdt_ping(wdd);
		if (ret)
			dev_err(wdd->parent,
				"%s: watchdog restart failed, ret=%d\n",
				__func__, ret);
	}

	return ret;
}

static int pcf2127_wdt_start(struct watchdog_device *wdd)
{
	return pcf2127_wdt_ping(wdd);
}

static int pcf2127_wdt_stop(struct watchdog_device *wdd)
{
	struct pcf2127 *pcf2127 = watchdog_get_drvdata(wdd);

	return regmap_write(pcf2127->regmap, PCF2127_REG_WD_VAL,
			    PCF2127_WD_VAL_STOP);
}

static int pcf2127_wdt_set_timeout(struct watchdog_device *wdd,
				   unsigned int new_timeout)
{
	dev_dbg(wdd->parent, "new watchdog timeout: %is (old: %is)\n",
		new_timeout, wdd->timeout);

	wdd->timeout = new_timeout;

	return pcf2127_wdt_active_ping(wdd);
}

static const struct watchdog_info pcf2127_wdt_info = {
	.identity = "NXP PCF2127/PCF2129 Watchdog",
	.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
};

static const struct watchdog_ops pcf2127_watchdog_ops = {
	.owner = THIS_MODULE,
	.start = pcf2127_wdt_start,
	.stop = pcf2127_wdt_stop,
	.ping = pcf2127_wdt_ping,
	.set_timeout = pcf2127_wdt_set_timeout,
};

static int pcf2127_watchdog_init(struct device *dev, struct pcf2127 *pcf2127)
{
	u32 wdd_timeout;
	int ret;

	if (!IS_ENABLED(CONFIG_WATCHDOG) ||
	    !device_property_read_bool(dev, "reset-source"))
		return 0;

	pcf2127->wdd.parent = dev;
	pcf2127->wdd.info = &pcf2127_wdt_info;
	pcf2127->wdd.ops = &pcf2127_watchdog_ops;
	pcf2127->wdd.min_timeout = PCF2127_WD_VAL_MIN;
	pcf2127->wdd.max_timeout = PCF2127_WD_VAL_MAX;
	pcf2127->wdd.timeout = PCF2127_WD_VAL_DEFAULT;
	pcf2127->wdd.min_hw_heartbeat_ms = 500;
	pcf2127->wdd.status = WATCHDOG_NOWAYOUT_INIT_STATUS;

	watchdog_set_drvdata(&pcf2127->wdd, pcf2127);

	/* Test if watchdog timer is started by bootloader */
	ret = regmap_read(pcf2127->regmap, PCF2127_REG_WD_VAL, &wdd_timeout);
	if (ret)
		return ret;

	if (wdd_timeout)
		set_bit(WDOG_HW_RUNNING, &pcf2127->wdd.status);

	return devm_watchdog_register_device(dev, &pcf2127->wdd);
}

/* Alarm */
static int pcf2127_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
	unsigned int buf[5], ctrl2;
	int ret;

	ret = regmap_read(pcf2127->regmap, PCF2127_REG_CTRL2, &ctrl2);
	if (ret)
		return ret;

	ret = pcf2127_wdt_active_ping(&pcf2127->wdd);
	if (ret)
		return ret;

	ret = regmap_bulk_read(pcf2127->regmap, PCF2127_REG_ALARM_SC, buf,
			       sizeof(buf));
	if (ret)
		return ret;

	alrm->enabled = ctrl2 & PCF2127_BIT_CTRL2_AIE;
	alrm->pending = ctrl2 & PCF2127_BIT_CTRL2_AF;

	alrm->time.tm_sec = bcd2bin(buf[0] & 0x7F);
	alrm->time.tm_min = bcd2bin(buf[1] & 0x7F);
	alrm->time.tm_hour = bcd2bin(buf[2] & 0x3F);
	alrm->time.tm_mday = bcd2bin(buf[3] & 0x3F);

	return 0;
}

static int pcf2127_rtc_alarm_irq_enable(struct device *dev, u32 enable)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
	int ret;

	ret = regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL2,
				 PCF2127_BIT_CTRL2_AIE,
				 enable ? PCF2127_BIT_CTRL2_AIE : 0);
	if (ret)
		return ret;

	return pcf2127_wdt_active_ping(&pcf2127->wdd);
}

static int pcf2127_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
	uint8_t buf[5];
	int ret;

	ret = regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL2,
				 PCF2127_BIT_CTRL2_AF, 0);
	if (ret)
		return ret;

	ret = pcf2127_wdt_active_ping(&pcf2127->wdd);
	if (ret)
		return ret;

	buf[0] = bin2bcd(alrm->time.tm_sec);
	buf[1] = bin2bcd(alrm->time.tm_min);
	buf[2] = bin2bcd(alrm->time.tm_hour);
	buf[3] = bin2bcd(alrm->time.tm_mday);
	buf[4] = PCF2127_BIT_ALARM_AE; /* Do not match on week day */

	ret = regmap_bulk_write(pcf2127->regmap, PCF2127_REG_ALARM_SC, buf,
				sizeof(buf));
	if (ret)
		return ret;

	return pcf2127_rtc_alarm_irq_enable(dev, alrm->enabled);
}

static irqreturn_t pcf2127_rtc_irq(int irq, void *dev)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
	unsigned int ctrl2 = 0;
	int ret = 0;

	ret = regmap_read(pcf2127->regmap, PCF2127_REG_CTRL2, &ctrl2);
	if (ret)
		return IRQ_NONE;

	if (!(ctrl2 & PCF2127_BIT_CTRL2_AF))
		return IRQ_NONE;

	regmap_write(pcf2127->regmap, PCF2127_REG_CTRL2,
		     ctrl2 & ~(PCF2127_BIT_CTRL2_AF | PCF2127_BIT_CTRL2_WDTF));

	rtc_update_irq(pcf2127->rtc, 1, RTC_IRQF | RTC_AF);

	pcf2127_wdt_active_ping(&pcf2127->wdd);

	return IRQ_HANDLED;
}

static const struct rtc_class_ops pcf2127_rtc_ops = {
	.ioctl            = pcf2127_rtc_ioctl,
	.read_time        = pcf2127_rtc_read_time,
	.set_time         = pcf2127_rtc_set_time,
	.read_alarm       = pcf2127_rtc_read_alarm,
	.set_alarm        = pcf2127_rtc_set_alarm,
	.alarm_irq_enable = pcf2127_rtc_alarm_irq_enable,
};

/* sysfs interface */

static ssize_t timestamp0_store(struct device *dev,
				struct device_attribute *attr,
				const char *buf, size_t count)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev->parent);
	int ret;

	ret = regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL1,
				 PCF2127_BIT_CTRL1_TSF1, 0);
	if (ret) {
		dev_err(dev, "%s: update ctrl1 ret=%d\n", __func__, ret);
		return ret;
	}

	ret = regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL2,
				 PCF2127_BIT_CTRL2_TSF2, 0);
	if (ret) {
		dev_err(dev, "%s: update ctrl2 ret=%d\n", __func__, ret);
		return ret;
	}

	ret = pcf2127_wdt_active_ping(&pcf2127->wdd);
	if (ret)
		return ret;

	return count;
};

static ssize_t timestamp0_show(struct device *dev,
			       struct device_attribute *attr, char *buf)
{
	struct pcf2127 *pcf2127 = dev_get_drvdata(dev->parent);
	struct rtc_time tm;
	int ret;
	unsigned char data[25];

	ret = regmap_bulk_read(pcf2127->regmap, PCF2127_REG_CTRL1, data,
			       sizeof(data));
	if (ret) {
		dev_err(dev, "%s: read error ret=%d\n", __func__, ret);
		return ret;
	}

	dev_dbg(dev,
		"%s: raw data is cr1=%02x, cr2=%02x, cr3=%02x, ts_sc=%02x, "
		"ts_mn=%02x, ts_hr=%02x, ts_dm=%02x, ts_mo=%02x, ts_yr=%02x\n",
		__func__, data[PCF2127_REG_CTRL1], data[PCF2127_REG_CTRL2],
		data[PCF2127_REG_CTRL3], data[PCF2127_REG_TS_SC],
		data[PCF2127_REG_TS_MN], data[PCF2127_REG_TS_HR],
		data[PCF2127_REG_TS_DM], data[PCF2127_REG_TS_MO],
		data[PCF2127_REG_TS_YR]);

	ret = pcf2127_wdt_active_ping(&pcf2127->wdd);
	if (ret)
		return ret;

	if (!(data[PCF2127_REG_CTRL1] & PCF2127_BIT_CTRL1_TSF1) &&
	    !(data[PCF2127_REG_CTRL2] & PCF2127_BIT_CTRL2_TSF2))
		return 0;

	tm.tm_sec = bcd2bin(data[PCF2127_REG_TS_SC] & 0x7F);
	tm.tm_min = bcd2bin(data[PCF2127_REG_TS_MN] & 0x7F);
	tm.tm_hour = bcd2bin(data[PCF2127_REG_TS_HR] & 0x3F);
	tm.tm_mday = bcd2bin(data[PCF2127_REG_TS_DM] & 0x3F);
	/* TS_MO register (month) value range: 1-12 */
	tm.tm_mon = bcd2bin(data[PCF2127_REG_TS_MO] & 0x1F) - 1;
	tm.tm_year = bcd2bin(data[PCF2127_REG_TS_YR]);
	if (tm.tm_year < 70)
		tm.tm_year += 100; /* assume we are in 1970...2069 */

	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 struct attribute *pcf2127_attrs[] = {
	&dev_attr_timestamp0.attr,
	NULL
};

static const struct attribute_group pcf2127_attr_group = {
	.attrs	= pcf2127_attrs,
};

static int pcf2127_probe(struct device *dev, struct regmap *regmap,
			 int alarm_irq, const char *name, bool is_pcf2127)
{
	struct pcf2127 *pcf2127;
	int ret = 0;
	unsigned int val;

	dev_dbg(dev, "%s\n", __func__);

	pcf2127 = devm_kzalloc(dev, sizeof(*pcf2127), GFP_KERNEL);
	if (!pcf2127)
		return -ENOMEM;

	pcf2127->regmap = regmap;

	dev_set_drvdata(dev, pcf2127);

	pcf2127->rtc = devm_rtc_allocate_device(dev);
	if (IS_ERR(pcf2127->rtc))
		return PTR_ERR(pcf2127->rtc);

	pcf2127->rtc->ops = &pcf2127_rtc_ops;
	pcf2127->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
	pcf2127->rtc->range_max = RTC_TIMESTAMP_END_2099;
	pcf2127->rtc->set_start_time = true; /* Sets actual start to 1970 */
	pcf2127->rtc->uie_unsupported = 1;
	clear_bit(RTC_FEATURE_ALARM, pcf2127->rtc->features);

	if (alarm_irq > 0) {
		ret = devm_request_threaded_irq(dev, alarm_irq, NULL,
						pcf2127_rtc_irq,
						IRQF_TRIGGER_LOW | IRQF_ONESHOT,
						dev_name(dev), dev);
		if (ret) {
			dev_err(dev, "failed to request alarm irq\n");
			return ret;
		}
	}

	if (alarm_irq > 0 || device_property_read_bool(dev, "wakeup-source")) {
		device_init_wakeup(dev, true);
		set_bit(RTC_FEATURE_ALARM, pcf2127->rtc->features);
	}

	if (is_pcf2127) {
		struct nvmem_config nvmem_cfg = {
			.priv = pcf2127,
			.reg_read = pcf2127_nvmem_read,
			.reg_write = pcf2127_nvmem_write,
			.size = 512,
		};

		ret = devm_rtc_nvmem_register(pcf2127->rtc, &nvmem_cfg);
	}

	/*
	 * The "Power-On Reset Override" facility prevents the RTC to do a reset
	 * after power on. For normal operation the PORO must be disabled.
	 */
	regmap_clear_bits(pcf2127->regmap, PCF2127_REG_CTRL1,
				PCF2127_BIT_CTRL1_POR_OVRD);

	ret = regmap_read(pcf2127->regmap, PCF2127_REG_CLKOUT, &val);
	if (ret < 0)
		return ret;

	if (!(val & PCF2127_BIT_CLKOUT_OTPR)) {
		ret = regmap_set_bits(pcf2127->regmap, PCF2127_REG_CLKOUT,
				      PCF2127_BIT_CLKOUT_OTPR);
		if (ret < 0)
			return ret;

		msleep(100);
	}

	/*
	 * Watchdog timer enabled and reset pin /RST activated when timed out.
	 * Select 1Hz clock source for watchdog timer.
	 * Note: Countdown timer disabled and not available.
	 * For pca2129, pcf2129, only bit[7] is for Symbol WD_CD
	 * of register watchdg_tim_ctl. The bit[6] is labeled
	 * as T. Bits labeled as T must always be written with
	 * logic 0.
	 */
	ret = regmap_update_bits(pcf2127->regmap, PCF2127_REG_WD_CTL,
				 PCF2127_BIT_WD_CTL_CD1 |
				 PCF2127_BIT_WD_CTL_CD0 |
				 PCF2127_BIT_WD_CTL_TF1 |
				 PCF2127_BIT_WD_CTL_TF0,
				 PCF2127_BIT_WD_CTL_CD1 |
				 (is_pcf2127 ? PCF2127_BIT_WD_CTL_CD0 : 0) |
				 PCF2127_BIT_WD_CTL_TF1);
	if (ret) {
		dev_err(dev, "%s: watchdog config (wd_ctl) failed\n", __func__);
		return ret;
	}

	pcf2127_watchdog_init(dev, pcf2127);

	/*
	 * Disable battery low/switch-over timestamp and interrupts.
	 * Clear battery interrupt flags which can block new trigger events.
	 * Note: This is the default chip behaviour but added to ensure
	 * correct tamper timestamp and interrupt function.
	 */
	ret = regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL3,
				 PCF2127_BIT_CTRL3_BTSE |
				 PCF2127_BIT_CTRL3_BIE |
				 PCF2127_BIT_CTRL3_BLIE, 0);
	if (ret) {
		dev_err(dev, "%s: interrupt config (ctrl3) failed\n",
			__func__);
		return ret;
	}

	/*
	 * Enable timestamp function and store timestamp of first trigger
	 * event until TSF1 and TFS2 interrupt flags are cleared.
	 */
	ret = regmap_update_bits(pcf2127->regmap, PCF2127_REG_TS_CTRL,
				 PCF2127_BIT_TS_CTRL_TSOFF |
				 PCF2127_BIT_TS_CTRL_TSM,
				 PCF2127_BIT_TS_CTRL_TSM);
	if (ret) {
		dev_err(dev, "%s: tamper detection config (ts_ctrl) failed\n",
			__func__);
		return ret;
	}

	/*
	 * Enable interrupt generation when TSF1 or TSF2 timestamp flags
	 * are set. Interrupt signal is an open-drain output and can be
	 * left floating if unused.
	 */
	ret = regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL2,
				 PCF2127_BIT_CTRL2_TSIE,
				 PCF2127_BIT_CTRL2_TSIE);
	if (ret) {
		dev_err(dev, "%s: tamper detection config (ctrl2) failed\n",
			__func__);
		return ret;
	}

	ret = rtc_add_group(pcf2127->rtc, &pcf2127_attr_group);
	if (ret) {
		dev_err(dev, "%s: tamper sysfs registering failed\n",
			__func__);
		return ret;
	}

	return devm_rtc_register_device(pcf2127->rtc);
}

#ifdef CONFIG_OF
static const struct of_device_id pcf2127_of_match[] = {
	{ .compatible = "nxp,pcf2127" },
	{ .compatible = "nxp,pcf2129" },
	{ .compatible = "nxp,pca2129" },
	{}
};
MODULE_DEVICE_TABLE(of, pcf2127_of_match);
#endif

#if IS_ENABLED(CONFIG_I2C)

static int pcf2127_i2c_write(void *context, const void *data, size_t count)
{
	struct device *dev = context;
	struct i2c_client *client = to_i2c_client(dev);
	int ret;

	ret = i2c_master_send(client, data, count);
	if (ret != count)
		return ret < 0 ? ret : -EIO;

	return 0;
}

static int pcf2127_i2c_gather_write(void *context,
				const void *reg, size_t reg_size,
				const void *val, size_t val_size)
{
	struct device *dev = context;
	struct i2c_client *client = to_i2c_client(dev);
	int ret;
	void *buf;

	if (WARN_ON(reg_size != 1))
		return -EINVAL;

	buf = kmalloc(val_size + 1, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	memcpy(buf, reg, 1);
	memcpy(buf + 1, val, val_size);

	ret = i2c_master_send(client, buf, val_size + 1);

	kfree(buf);

	if (ret != val_size + 1)
		return ret < 0 ? ret : -EIO;

	return 0;
}

static int pcf2127_i2c_read(void *context, const void *reg, size_t reg_size,
				void *val, size_t val_size)
{
	struct device *dev = context;
	struct i2c_client *client = to_i2c_client(dev);
	int ret;

	if (WARN_ON(reg_size != 1))
		return -EINVAL;

	ret = i2c_master_send(client, reg, 1);
	if (ret != 1)
		return ret < 0 ? ret : -EIO;

	ret = i2c_master_recv(client, val, val_size);
	if (ret != val_size)
		return ret < 0 ? ret : -EIO;

	return 0;
}

/*
 * The reason we need this custom regmap_bus instead of using regmap_init_i2c()
 * is that the STOP condition is required between set register address and
 * read register data when reading from registers.
 */
static const struct regmap_bus pcf2127_i2c_regmap = {
	.write = pcf2127_i2c_write,
	.gather_write = pcf2127_i2c_gather_write,
	.read = pcf2127_i2c_read,
};

static struct i2c_driver pcf2127_i2c_driver;

static int pcf2127_i2c_probe(struct i2c_client *client,
				const struct i2c_device_id *id)
{
	struct regmap *regmap;
	static const struct regmap_config config = {
		.reg_bits = 8,
		.val_bits = 8,
		.max_register = 0x1d,
	};

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
		return -ENODEV;

	regmap = devm_regmap_init(&client->dev, &pcf2127_i2c_regmap,
					&client->dev, &config);
	if (IS_ERR(regmap)) {
		dev_err(&client->dev, "%s: regmap allocation failed: %ld\n",
			__func__, PTR_ERR(regmap));
		return PTR_ERR(regmap);
	}

	return pcf2127_probe(&client->dev, regmap, client->irq,
			     pcf2127_i2c_driver.driver.name, id->driver_data);
}

static const struct i2c_device_id pcf2127_i2c_id[] = {
	{ "pcf2127", 1 },
	{ "pcf2129", 0 },
	{ "pca2129", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, pcf2127_i2c_id);

static struct i2c_driver pcf2127_i2c_driver = {
	.driver		= {
		.name	= "rtc-pcf2127-i2c",
		.of_match_table = of_match_ptr(pcf2127_of_match),
	},
	.probe		= pcf2127_i2c_probe,
	.id_table	= pcf2127_i2c_id,
};

static int pcf2127_i2c_register_driver(void)
{
	return i2c_add_driver(&pcf2127_i2c_driver);
}

static void pcf2127_i2c_unregister_driver(void)
{
	i2c_del_driver(&pcf2127_i2c_driver);
}

#else

static int pcf2127_i2c_register_driver(void)
{
	return 0;
}

static void pcf2127_i2c_unregister_driver(void)
{
}

#endif

#if IS_ENABLED(CONFIG_SPI_MASTER)

static struct spi_driver pcf2127_spi_driver;

static int pcf2127_spi_probe(struct spi_device *spi)
{
	static const struct regmap_config config = {
		.reg_bits = 8,
		.val_bits = 8,
		.read_flag_mask = 0xa0,
		.write_flag_mask = 0x20,
		.max_register = 0x1d,
	};
	struct regmap *regmap;

	regmap = devm_regmap_init_spi(spi, &config);
	if (IS_ERR(regmap)) {
		dev_err(&spi->dev, "%s: regmap allocation failed: %ld\n",
			__func__, PTR_ERR(regmap));
		return PTR_ERR(regmap);
	}

	return pcf2127_probe(&spi->dev, regmap, spi->irq,
			     pcf2127_spi_driver.driver.name,
			     spi_get_device_id(spi)->driver_data);
}

static const struct spi_device_id pcf2127_spi_id[] = {
	{ "pcf2127", 1 },
	{ "pcf2129", 0 },
	{ "pca2129", 0 },
	{ }
};
MODULE_DEVICE_TABLE(spi, pcf2127_spi_id);

static struct spi_driver pcf2127_spi_driver = {
	.driver		= {
		.name	= "rtc-pcf2127-spi",
		.of_match_table = of_match_ptr(pcf2127_of_match),
	},
	.probe		= pcf2127_spi_probe,
	.id_table	= pcf2127_spi_id,
};

static int pcf2127_spi_register_driver(void)
{
	return spi_register_driver(&pcf2127_spi_driver);
}

static void pcf2127_spi_unregister_driver(void)
{
	spi_unregister_driver(&pcf2127_spi_driver);
}

#else

static int pcf2127_spi_register_driver(void)
{
	return 0;
}

static void pcf2127_spi_unregister_driver(void)
{
}

#endif

static int __init pcf2127_init(void)
{
	int ret;

	ret = pcf2127_i2c_register_driver();
	if (ret) {
		pr_err("Failed to register pcf2127 i2c driver: %d\n", ret);
		return ret;
	}

	ret = pcf2127_spi_register_driver();
	if (ret) {
		pr_err("Failed to register pcf2127 spi driver: %d\n", ret);
		pcf2127_i2c_unregister_driver();
	}

	return ret;
}
module_init(pcf2127_init)

static void __exit pcf2127_exit(void)
{
	pcf2127_spi_unregister_driver();
	pcf2127_i2c_unregister_driver();
}
module_exit(pcf2127_exit)

MODULE_AUTHOR("Renaud Cerrato <r.cerrato@til-technologies.fr>");
MODULE_DESCRIPTION("NXP PCF2127/29 RTC driver");
MODULE_LICENSE("GPL v2");