Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1016 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
new file mode 100644
index 000000000..8a89bc52b
--- /dev/null
+++ b/drivers/rtc/rtc-m41t80.c
@@ -0,0 +1,1016 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * I2C client/driver for the ST M41T80 family of i2c rtc chips.
+ *
+ * Author: Alexander Bigga <ab@mycable.de>
+ *
+ * Based on m41t00.c by Mark A. Greer <mgreer@mvista.com>
+ *
+ * 2006 (c) mycable GmbH
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/bcd.h>
+#include <linux/clk-provider.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/string.h>
+#ifdef CONFIG_RTC_DRV_M41T80_WDT
+#include <linux/fs.h>
+#include <linux/ioctl.h>
+#include <linux/miscdevice.h>
+#include <linux/reboot.h>
+#include <linux/watchdog.h>
+#endif
+
+#define M41T80_REG_SSEC		0x00
+#define M41T80_REG_SEC		0x01
+#define M41T80_REG_MIN		0x02
+#define M41T80_REG_HOUR		0x03
+#define M41T80_REG_WDAY		0x04
+#define M41T80_REG_DAY		0x05
+#define M41T80_REG_MON		0x06
+#define M41T80_REG_YEAR		0x07
+#define M41T80_REG_ALARM_MON	0x0a
+#define M41T80_REG_ALARM_DAY	0x0b
+#define M41T80_REG_ALARM_HOUR	0x0c
+#define M41T80_REG_ALARM_MIN	0x0d
+#define M41T80_REG_ALARM_SEC	0x0e
+#define M41T80_REG_FLAGS	0x0f
+#define M41T80_REG_SQW		0x13
+
+#define M41T80_DATETIME_REG_SIZE	(M41T80_REG_YEAR + 1)
+#define M41T80_ALARM_REG_SIZE	\
+	(M41T80_REG_ALARM_SEC + 1 - M41T80_REG_ALARM_MON)
+
+#define M41T80_SQW_MAX_FREQ	32768
+
+#define M41T80_SEC_ST		BIT(7)	/* ST: Stop Bit */
+#define M41T80_ALMON_AFE	BIT(7)	/* AFE: AF Enable Bit */
+#define M41T80_ALMON_SQWE	BIT(6)	/* SQWE: SQW Enable Bit */
+#define M41T80_ALHOUR_HT	BIT(6)	/* HT: Halt Update Bit */
+#define M41T80_FLAGS_OF		BIT(2)	/* OF: Oscillator Failure Bit */
+#define M41T80_FLAGS_AF		BIT(6)	/* AF: Alarm Flag Bit */
+#define M41T80_FLAGS_BATT_LOW	BIT(4)	/* BL: Battery Low Bit */
+#define M41T80_WATCHDOG_RB2	BIT(7)	/* RB: Watchdog resolution */
+#define M41T80_WATCHDOG_RB1	BIT(1)	/* RB: Watchdog resolution */
+#define M41T80_WATCHDOG_RB0	BIT(0)	/* RB: Watchdog resolution */
+
+#define M41T80_FEATURE_HT	BIT(0)	/* Halt feature */
+#define M41T80_FEATURE_BL	BIT(1)	/* Battery low indicator */
+#define M41T80_FEATURE_SQ	BIT(2)	/* Squarewave feature */
+#define M41T80_FEATURE_WD	BIT(3)	/* Extra watchdog resolution */
+#define M41T80_FEATURE_SQ_ALT	BIT(4)	/* RSx bits are in reg 4 */
+
+static const struct i2c_device_id m41t80_id[] = {
+	{ "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT },
+	{ "m41t65", M41T80_FEATURE_HT | M41T80_FEATURE_WD },
+	{ "m41t80", M41T80_FEATURE_SQ },
+	{ "m41t81", M41T80_FEATURE_HT | M41T80_FEATURE_SQ},
+	{ "m41t81s", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+	{ "m41t82", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+	{ "m41t83", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+	{ "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+	{ "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+	{ "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+	{ "rv4162", M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, m41t80_id);
+
+static const struct of_device_id m41t80_of_match[] = {
+	{
+		.compatible = "st,m41t62",
+		.data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT)
+	},
+	{
+		.compatible = "st,m41t65",
+		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_WD)
+	},
+	{
+		.compatible = "st,m41t80",
+		.data = (void *)(M41T80_FEATURE_SQ)
+	},
+	{
+		.compatible = "st,m41t81",
+		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_SQ)
+	},
+	{
+		.compatible = "st,m41t81s",
+		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
+	},
+	{
+		.compatible = "st,m41t82",
+		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
+	},
+	{
+		.compatible = "st,m41t83",
+		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
+	},
+	{
+		.compatible = "st,m41t84",
+		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
+	},
+	{
+		.compatible = "st,m41t85",
+		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
+	},
+	{
+		.compatible = "st,m41t87",
+		.data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
+	},
+	{
+		.compatible = "microcrystal,rv4162",
+		.data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
+	},
+	/* DT compatibility only, do not use compatibles below: */
+	{
+		.compatible = "st,rv4162",
+		.data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
+	},
+	{
+		.compatible = "rv4162",
+		.data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, m41t80_of_match);
+
+struct m41t80_data {
+	unsigned long features;
+	struct i2c_client *client;
+	struct rtc_device *rtc;
+#ifdef CONFIG_COMMON_CLK
+	struct clk_hw sqw;
+	unsigned long freq;
+	unsigned int sqwe;
+#endif
+};
+
+static irqreturn_t m41t80_handle_irq(int irq, void *dev_id)
+{
+	struct i2c_client *client = dev_id;
+	struct m41t80_data *m41t80 = i2c_get_clientdata(client);
+	struct mutex *lock = &m41t80->rtc->ops_lock;
+	unsigned long events = 0;
+	int flags, flags_afe;
+
+	mutex_lock(lock);
+
+	flags_afe = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
+	if (flags_afe < 0) {
+		mutex_unlock(lock);
+		return IRQ_NONE;
+	}
+
+	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
+	if (flags <= 0) {
+		mutex_unlock(lock);
+		return IRQ_NONE;
+	}
+
+	if (flags & M41T80_FLAGS_AF) {
+		flags &= ~M41T80_FLAGS_AF;
+		flags_afe &= ~M41T80_ALMON_AFE;
+		events |= RTC_AF;
+	}
+
+	if (events) {
+		rtc_update_irq(m41t80->rtc, 1, events);
+		i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS, flags);
+		i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
+					  flags_afe);
+	}
+
+	mutex_unlock(lock);
+
+	return IRQ_HANDLED;
+}
+
+static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned char buf[8];
+	int err, flags;
+
+	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
+	if (flags < 0)
+		return flags;
+
+	if (flags & M41T80_FLAGS_OF) {
+		dev_err(&client->dev, "Oscillator failure, data is invalid.\n");
+		return -EINVAL;
+	}
+
+	err = i2c_smbus_read_i2c_block_data(client, M41T80_REG_SSEC,
+					    sizeof(buf), buf);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to read date\n");
+		return err;
+	}
+
+	tm->tm_sec = bcd2bin(buf[M41T80_REG_SEC] & 0x7f);
+	tm->tm_min = bcd2bin(buf[M41T80_REG_MIN] & 0x7f);
+	tm->tm_hour = bcd2bin(buf[M41T80_REG_HOUR] & 0x3f);
+	tm->tm_mday = bcd2bin(buf[M41T80_REG_DAY] & 0x3f);
+	tm->tm_wday = buf[M41T80_REG_WDAY] & 0x07;
+	tm->tm_mon = bcd2bin(buf[M41T80_REG_MON] & 0x1f) - 1;
+
+	/* assume 20YY not 19YY, and ignore the Century Bit */
+	tm->tm_year = bcd2bin(buf[M41T80_REG_YEAR]) + 100;
+	return 0;
+}
+
+static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct m41t80_data *clientdata = i2c_get_clientdata(client);
+	unsigned char buf[8];
+	int err, flags;
+
+	buf[M41T80_REG_SSEC] = 0;
+	buf[M41T80_REG_SEC] = bin2bcd(tm->tm_sec);
+	buf[M41T80_REG_MIN] = bin2bcd(tm->tm_min);
+	buf[M41T80_REG_HOUR] = bin2bcd(tm->tm_hour);
+	buf[M41T80_REG_DAY] = bin2bcd(tm->tm_mday);
+	buf[M41T80_REG_MON] = bin2bcd(tm->tm_mon + 1);
+	buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year - 100);
+	buf[M41T80_REG_WDAY] = tm->tm_wday;
+
+	/* If the square wave output is controlled in the weekday register */
+	if (clientdata->features & M41T80_FEATURE_SQ_ALT) {
+		int val;
+
+		val = i2c_smbus_read_byte_data(client, M41T80_REG_WDAY);
+		if (val < 0)
+			return val;
+
+		buf[M41T80_REG_WDAY] |= (val & 0xf0);
+	}
+
+	err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_SSEC,
+					     sizeof(buf), buf);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write to date registers\n");
+		return err;
+	}
+
+	/* Clear the OF bit of Flags Register */
+	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
+	if (flags < 0)
+		return flags;
+
+	err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS,
+					flags & ~M41T80_FLAGS_OF);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write flags register\n");
+		return err;
+	}
+
+	return err;
+}
+
+static int m41t80_rtc_proc(struct device *dev, struct seq_file *seq)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct m41t80_data *clientdata = i2c_get_clientdata(client);
+	int reg;
+
+	if (clientdata->features & M41T80_FEATURE_BL) {
+		reg = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
+		if (reg < 0)
+			return reg;
+		seq_printf(seq, "battery\t\t: %s\n",
+			   (reg & M41T80_FLAGS_BATT_LOW) ? "exhausted" : "ok");
+	}
+	return 0;
+}
+
+static int m41t80_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	int flags, retval;
+
+	flags = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
+	if (flags < 0)
+		return flags;
+
+	if (enabled)
+		flags |= M41T80_ALMON_AFE;
+	else
+		flags &= ~M41T80_ALMON_AFE;
+
+	retval = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, flags);
+	if (retval < 0) {
+		dev_err(dev, "Unable to enable alarm IRQ %d\n", retval);
+		return retval;
+	}
+	return 0;
+}
+
+static int m41t80_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	u8 alarmvals[5];
+	int ret, err;
+
+	alarmvals[0] = bin2bcd(alrm->time.tm_mon + 1);
+	alarmvals[1] = bin2bcd(alrm->time.tm_mday);
+	alarmvals[2] = bin2bcd(alrm->time.tm_hour);
+	alarmvals[3] = bin2bcd(alrm->time.tm_min);
+	alarmvals[4] = bin2bcd(alrm->time.tm_sec);
+
+	/* Clear AF and AFE flags */
+	ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
+	if (ret < 0)
+		return ret;
+	err = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
+					ret & ~(M41T80_ALMON_AFE));
+	if (err < 0) {
+		dev_err(dev, "Unable to clear AFE bit\n");
+		return err;
+	}
+
+	/* Keep SQWE bit value */
+	alarmvals[0] |= (ret & M41T80_ALMON_SQWE);
+
+	ret = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
+	if (ret < 0)
+		return ret;
+
+	err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS,
+					ret & ~(M41T80_FLAGS_AF));
+	if (err < 0) {
+		dev_err(dev, "Unable to clear AF bit\n");
+		return err;
+	}
+
+	/* Write the alarm */
+	err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_ALARM_MON,
+					     5, alarmvals);
+	if (err)
+		return err;
+
+	/* Enable the alarm interrupt */
+	if (alrm->enabled) {
+		alarmvals[0] |= M41T80_ALMON_AFE;
+		err = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
+						alarmvals[0]);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int m41t80_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	u8 alarmvals[5];
+	int flags, ret;
+
+	ret = i2c_smbus_read_i2c_block_data(client, M41T80_REG_ALARM_MON,
+					    5, alarmvals);
+	if (ret != 5)
+		return ret < 0 ? ret : -EIO;
+
+	flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
+	if (flags < 0)
+		return flags;
+
+	alrm->time.tm_sec  = bcd2bin(alarmvals[4] & 0x7f);
+	alrm->time.tm_min  = bcd2bin(alarmvals[3] & 0x7f);
+	alrm->time.tm_hour = bcd2bin(alarmvals[2] & 0x3f);
+	alrm->time.tm_mday = bcd2bin(alarmvals[1] & 0x3f);
+	alrm->time.tm_mon  = bcd2bin(alarmvals[0] & 0x3f) - 1;
+
+	alrm->enabled = !!(alarmvals[0] & M41T80_ALMON_AFE);
+	alrm->pending = (flags & M41T80_FLAGS_AF) && alrm->enabled;
+
+	return 0;
+}
+
+static struct rtc_class_ops m41t80_rtc_ops = {
+	.read_time = m41t80_rtc_read_time,
+	.set_time = m41t80_rtc_set_time,
+	.proc = m41t80_rtc_proc,
+};
+
+#ifdef CONFIG_PM_SLEEP
+static int m41t80_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	if (client->irq >= 0 && device_may_wakeup(dev))
+		enable_irq_wake(client->irq);
+
+	return 0;
+}
+
+static int m41t80_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	if (client->irq >= 0 && device_may_wakeup(dev))
+		disable_irq_wake(client->irq);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(m41t80_pm, m41t80_suspend, m41t80_resume);
+
+#ifdef CONFIG_COMMON_CLK
+#define sqw_to_m41t80_data(_hw) container_of(_hw, struct m41t80_data, sqw)
+
+static unsigned long m41t80_decode_freq(int setting)
+{
+	return (setting == 0) ? 0 : (setting == 1) ? M41T80_SQW_MAX_FREQ :
+		M41T80_SQW_MAX_FREQ >> setting;
+}
+
+static unsigned long m41t80_get_freq(struct m41t80_data *m41t80)
+{
+	struct i2c_client *client = m41t80->client;
+	int reg_sqw = (m41t80->features & M41T80_FEATURE_SQ_ALT) ?
+		M41T80_REG_WDAY : M41T80_REG_SQW;
+	int ret = i2c_smbus_read_byte_data(client, reg_sqw);
+
+	if (ret < 0)
+		return 0;
+	return m41t80_decode_freq(ret >> 4);
+}
+
+static unsigned long m41t80_sqw_recalc_rate(struct clk_hw *hw,
+					    unsigned long parent_rate)
+{
+	return sqw_to_m41t80_data(hw)->freq;
+}
+
+static long m41t80_sqw_round_rate(struct clk_hw *hw, unsigned long rate,
+				  unsigned long *prate)
+{
+	if (rate >= M41T80_SQW_MAX_FREQ)
+		return M41T80_SQW_MAX_FREQ;
+	if (rate >= M41T80_SQW_MAX_FREQ / 4)
+		return M41T80_SQW_MAX_FREQ / 4;
+	if (!rate)
+		return 0;
+	return 1 << ilog2(rate);
+}
+
+static int m41t80_sqw_set_rate(struct clk_hw *hw, unsigned long rate,
+			       unsigned long parent_rate)
+{
+	struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);
+	struct i2c_client *client = m41t80->client;
+	int reg_sqw = (m41t80->features & M41T80_FEATURE_SQ_ALT) ?
+		M41T80_REG_WDAY : M41T80_REG_SQW;
+	int reg, ret, val = 0;
+
+	if (rate >= M41T80_SQW_MAX_FREQ)
+		val = 1;
+	else if (rate >= M41T80_SQW_MAX_FREQ / 4)
+		val = 2;
+	else if (rate)
+		val = 15 - ilog2(rate);
+
+	reg = i2c_smbus_read_byte_data(client, reg_sqw);
+	if (reg < 0)
+		return reg;
+
+	reg = (reg & 0x0f) | (val << 4);
+
+	ret = i2c_smbus_write_byte_data(client, reg_sqw, reg);
+	if (!ret)
+		m41t80->freq = m41t80_decode_freq(val);
+	return ret;
+}
+
+static int m41t80_sqw_control(struct clk_hw *hw, bool enable)
+{
+	struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);
+	struct i2c_client *client = m41t80->client;
+	int ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
+
+	if (ret < 0)
+		return ret;
+
+	if (enable)
+		ret |= M41T80_ALMON_SQWE;
+	else
+		ret &= ~M41T80_ALMON_SQWE;
+
+	ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, ret);
+	if (!ret)
+		m41t80->sqwe = enable;
+	return ret;
+}
+
+static int m41t80_sqw_prepare(struct clk_hw *hw)
+{
+	return m41t80_sqw_control(hw, 1);
+}
+
+static void m41t80_sqw_unprepare(struct clk_hw *hw)
+{
+	m41t80_sqw_control(hw, 0);
+}
+
+static int m41t80_sqw_is_prepared(struct clk_hw *hw)
+{
+	return sqw_to_m41t80_data(hw)->sqwe;
+}
+
+static const struct clk_ops m41t80_sqw_ops = {
+	.prepare = m41t80_sqw_prepare,
+	.unprepare = m41t80_sqw_unprepare,
+	.is_prepared = m41t80_sqw_is_prepared,
+	.recalc_rate = m41t80_sqw_recalc_rate,
+	.round_rate = m41t80_sqw_round_rate,
+	.set_rate = m41t80_sqw_set_rate,
+};
+
+static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80)
+{
+	struct i2c_client *client = m41t80->client;
+	struct device_node *node = client->dev.of_node;
+	struct clk *clk;
+	struct clk_init_data init;
+	int ret;
+
+	/* First disable the clock */
+	ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
+	if (ret < 0)
+		return ERR_PTR(ret);
+	ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
+					ret & ~(M41T80_ALMON_SQWE));
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	init.name = "m41t80-sqw";
+	init.ops = &m41t80_sqw_ops;
+	init.flags = 0;
+	init.parent_names = NULL;
+	init.num_parents = 0;
+	m41t80->sqw.init = &init;
+	m41t80->freq = m41t80_get_freq(m41t80);
+
+	/* optional override of the clockname */
+	of_property_read_string(node, "clock-output-names", &init.name);
+
+	/* register the clock */
+	clk = clk_register(&client->dev, &m41t80->sqw);
+	if (!IS_ERR(clk))
+		of_clk_add_provider(node, of_clk_src_simple_get, clk);
+
+	return clk;
+}
+#endif
+
+#ifdef CONFIG_RTC_DRV_M41T80_WDT
+/*
+ *****************************************************************************
+ *
+ * Watchdog Driver
+ *
+ *****************************************************************************
+ */
+static DEFINE_MUTEX(m41t80_rtc_mutex);
+static struct i2c_client *save_client;
+
+/* Default margin */
+#define WD_TIMO 60		/* 1..31 seconds */
+
+static int wdt_margin = WD_TIMO;
+module_param(wdt_margin, int, 0);
+MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 60s)");
+
+static unsigned long wdt_is_open;
+static int boot_flag;
+
+/**
+ *	wdt_ping:
+ *
+ *	Reload counter one with the watchdog timeout. We don't bother reloading
+ *	the cascade counter.
+ */
+static void wdt_ping(void)
+{
+	unsigned char i2c_data[2];
+	struct i2c_msg msgs1[1] = {
+		{
+			.addr	= save_client->addr,
+			.flags	= 0,
+			.len	= 2,
+			.buf	= i2c_data,
+		},
+	};
+	struct m41t80_data *clientdata = i2c_get_clientdata(save_client);
+
+	i2c_data[0] = 0x09;		/* watchdog register */
+
+	if (wdt_margin > 31)
+		i2c_data[1] = (wdt_margin & 0xFC) | 0x83; /* resolution = 4s */
+	else
+		/*
+		 * WDS = 1 (0x80), mulitplier = WD_TIMO, resolution = 1s (0x02)
+		 */
+		i2c_data[1] = wdt_margin << 2 | 0x82;
+
+	/*
+	 * M41T65 has three bits for watchdog resolution.  Don't set bit 7, as
+	 * that would be an invalid resolution.
+	 */
+	if (clientdata->features & M41T80_FEATURE_WD)
+		i2c_data[1] &= ~M41T80_WATCHDOG_RB2;
+
+	i2c_transfer(save_client->adapter, msgs1, 1);
+}
+
+/**
+ *	wdt_disable:
+ *
+ *	disables watchdog.
+ */
+static void wdt_disable(void)
+{
+	unsigned char i2c_data[2], i2c_buf[0x10];
+	struct i2c_msg msgs0[2] = {
+		{
+			.addr	= save_client->addr,
+			.flags	= 0,
+			.len	= 1,
+			.buf	= i2c_data,
+		},
+		{
+			.addr	= save_client->addr,
+			.flags	= I2C_M_RD,
+			.len	= 1,
+			.buf	= i2c_buf,
+		},
+	};
+	struct i2c_msg msgs1[1] = {
+		{
+			.addr	= save_client->addr,
+			.flags	= 0,
+			.len	= 2,
+			.buf	= i2c_data,
+		},
+	};
+
+	i2c_data[0] = 0x09;
+	i2c_transfer(save_client->adapter, msgs0, 2);
+
+	i2c_data[0] = 0x09;
+	i2c_data[1] = 0x00;
+	i2c_transfer(save_client->adapter, msgs1, 1);
+}
+
+/**
+ *	wdt_write:
+ *	@file: file handle to the watchdog
+ *	@buf: buffer to write (unused as data does not matter here
+ *	@count: count of bytes
+ *	@ppos: pointer to the position to write. No seeks allowed
+ *
+ *	A write to a watchdog device is defined as a keepalive signal. Any
+ *	write of data will do, as we we don't define content meaning.
+ */
+static ssize_t wdt_write(struct file *file, const char __user *buf,
+			 size_t count, loff_t *ppos)
+{
+	if (count) {
+		wdt_ping();
+		return 1;
+	}
+	return 0;
+}
+
+static ssize_t wdt_read(struct file *file, char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	return 0;
+}
+
+/**
+ *	wdt_ioctl:
+ *	@file: file handle to the device
+ *	@cmd: watchdog command
+ *	@arg: argument pointer
+ *
+ *	The watchdog API defines a common set of functions for all watchdogs
+ *	according to their available features. We only actually usefully support
+ *	querying capabilities and current status.
+ */
+static int wdt_ioctl(struct file *file, unsigned int cmd,
+		     unsigned long arg)
+{
+	int new_margin, rv;
+	static struct watchdog_info ident = {
+		.options = WDIOF_POWERUNDER | WDIOF_KEEPALIVEPING |
+			WDIOF_SETTIMEOUT,
+		.firmware_version = 1,
+		.identity = "M41T80 WTD"
+	};
+
+	switch (cmd) {
+	case WDIOC_GETSUPPORT:
+		return copy_to_user((struct watchdog_info __user *)arg, &ident,
+				    sizeof(ident)) ? -EFAULT : 0;
+
+	case WDIOC_GETSTATUS:
+	case WDIOC_GETBOOTSTATUS:
+		return put_user(boot_flag, (int __user *)arg);
+	case WDIOC_KEEPALIVE:
+		wdt_ping();
+		return 0;
+	case WDIOC_SETTIMEOUT:
+		if (get_user(new_margin, (int __user *)arg))
+			return -EFAULT;
+		/* Arbitrary, can't find the card's limits */
+		if (new_margin < 1 || new_margin > 124)
+			return -EINVAL;
+		wdt_margin = new_margin;
+		wdt_ping();
+		fallthrough;
+	case WDIOC_GETTIMEOUT:
+		return put_user(wdt_margin, (int __user *)arg);
+
+	case WDIOC_SETOPTIONS:
+		if (copy_from_user(&rv, (int __user *)arg, sizeof(int)))
+			return -EFAULT;
+
+		if (rv & WDIOS_DISABLECARD) {
+			pr_info("disable watchdog\n");
+			wdt_disable();
+		}
+
+		if (rv & WDIOS_ENABLECARD) {
+			pr_info("enable watchdog\n");
+			wdt_ping();
+		}
+
+		return -EINVAL;
+	}
+	return -ENOTTY;
+}
+
+static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
+			       unsigned long arg)
+{
+	int ret;
+
+	mutex_lock(&m41t80_rtc_mutex);
+	ret = wdt_ioctl(file, cmd, arg);
+	mutex_unlock(&m41t80_rtc_mutex);
+
+	return ret;
+}
+
+/**
+ *	wdt_open:
+ *	@inode: inode of device
+ *	@file: file handle to device
+ *
+ */
+static int wdt_open(struct inode *inode, struct file *file)
+{
+	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR) {
+		mutex_lock(&m41t80_rtc_mutex);
+		if (test_and_set_bit(0, &wdt_is_open)) {
+			mutex_unlock(&m41t80_rtc_mutex);
+			return -EBUSY;
+		}
+		/*
+		 *	Activate
+		 */
+		wdt_is_open = 1;
+		mutex_unlock(&m41t80_rtc_mutex);
+		return stream_open(inode, file);
+	}
+	return -ENODEV;
+}
+
+/**
+ *	wdt_close:
+ *	@inode: inode to board
+ *	@file: file handle to board
+ *
+ */
+static int wdt_release(struct inode *inode, struct file *file)
+{
+	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR)
+		clear_bit(0, &wdt_is_open);
+	return 0;
+}
+
+/**
+ *	notify_sys:
+ *	@this: our notifier block
+ *	@code: the event being reported
+ *	@unused: unused
+ *
+ *	Our notifier is called on system shutdowns. We want to turn the card
+ *	off at reboot otherwise the machine will reboot again during memory
+ *	test or worse yet during the following fsck. This would suck, in fact
+ *	trust me - if it happens it does suck.
+ */
+static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
+			  void *unused)
+{
+	if (code == SYS_DOWN || code == SYS_HALT)
+		/* Disable Watchdog */
+		wdt_disable();
+	return NOTIFY_DONE;
+}
+
+static const struct file_operations wdt_fops = {
+	.owner	= THIS_MODULE,
+	.read	= wdt_read,
+	.unlocked_ioctl = wdt_unlocked_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
+	.write	= wdt_write,
+	.open	= wdt_open,
+	.release = wdt_release,
+	.llseek = no_llseek,
+};
+
+static struct miscdevice wdt_dev = {
+	.minor = WATCHDOG_MINOR,
+	.name = "watchdog",
+	.fops = &wdt_fops,
+};
+
+/*
+ *	The WDT card needs to learn about soft shutdowns in order to
+ *	turn the timebomb registers off.
+ */
+static struct notifier_block wdt_notifier = {
+	.notifier_call = wdt_notify_sys,
+};
+#endif /* CONFIG_RTC_DRV_M41T80_WDT */
+
+/*
+ *****************************************************************************
+ *
+ *	Driver Interface
+ *
+ *****************************************************************************
+ */
+
+static int m41t80_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	int rc = 0;
+	struct rtc_time tm;
+	struct m41t80_data *m41t80_data = NULL;
+	bool wakeup_source = false;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_I2C_BLOCK |
+				     I2C_FUNC_SMBUS_BYTE_DATA)) {
+		dev_err(&adapter->dev, "doesn't support I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK\n");
+		return -ENODEV;
+	}
+
+	m41t80_data = devm_kzalloc(&client->dev, sizeof(*m41t80_data),
+				   GFP_KERNEL);
+	if (!m41t80_data)
+		return -ENOMEM;
+
+	m41t80_data->client = client;
+	if (client->dev.of_node)
+		m41t80_data->features = (unsigned long)
+			of_device_get_match_data(&client->dev);
+	else
+		m41t80_data->features = id->driver_data;
+	i2c_set_clientdata(client, m41t80_data);
+
+	m41t80_data->rtc =  devm_rtc_allocate_device(&client->dev);
+	if (IS_ERR(m41t80_data->rtc))
+		return PTR_ERR(m41t80_data->rtc);
+
+#ifdef CONFIG_OF
+	wakeup_source = of_property_read_bool(client->dev.of_node,
+					      "wakeup-source");
+#endif
+	if (client->irq > 0) {
+		rc = devm_request_threaded_irq(&client->dev, client->irq,
+					       NULL, m41t80_handle_irq,
+					       IRQF_TRIGGER_LOW | IRQF_ONESHOT,
+					       "m41t80", client);
+		if (rc) {
+			dev_warn(&client->dev, "unable to request IRQ, alarms disabled\n");
+			client->irq = 0;
+			wakeup_source = false;
+		}
+	}
+	if (client->irq > 0 || wakeup_source) {
+		m41t80_rtc_ops.read_alarm = m41t80_read_alarm;
+		m41t80_rtc_ops.set_alarm = m41t80_set_alarm;
+		m41t80_rtc_ops.alarm_irq_enable = m41t80_alarm_irq_enable;
+		/* Enable the wakealarm */
+		device_init_wakeup(&client->dev, true);
+	}
+
+	m41t80_data->rtc->ops = &m41t80_rtc_ops;
+	m41t80_data->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	m41t80_data->rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+	if (client->irq <= 0) {
+		/* We cannot support UIE mode if we do not have an IRQ line */
+		m41t80_data->rtc->uie_unsupported = 1;
+	}
+
+	/* Make sure HT (Halt Update) bit is cleared */
+	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);
+
+	if (rc >= 0 && rc & M41T80_ALHOUR_HT) {
+		if (m41t80_data->features & M41T80_FEATURE_HT) {
+			m41t80_rtc_read_time(&client->dev, &tm);
+			dev_info(&client->dev, "HT bit was set!\n");
+			dev_info(&client->dev, "Power Down at %ptR\n", &tm);
+		}
+		rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_HOUR,
+					       rc & ~M41T80_ALHOUR_HT);
+	}
+
+	if (rc < 0) {
+		dev_err(&client->dev, "Can't clear HT bit\n");
+		return rc;
+	}
+
+	/* Make sure ST (stop) bit is cleared */
+	rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);
+
+	if (rc >= 0 && rc & M41T80_SEC_ST)
+		rc = i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
+					       rc & ~M41T80_SEC_ST);
+	if (rc < 0) {
+		dev_err(&client->dev, "Can't clear ST bit\n");
+		return rc;
+	}
+
+#ifdef CONFIG_RTC_DRV_M41T80_WDT
+	if (m41t80_data->features & M41T80_FEATURE_HT) {
+		save_client = client;
+		rc = misc_register(&wdt_dev);
+		if (rc)
+			return rc;
+		rc = register_reboot_notifier(&wdt_notifier);
+		if (rc) {
+			misc_deregister(&wdt_dev);
+			return rc;
+		}
+	}
+#endif
+#ifdef CONFIG_COMMON_CLK
+	if (m41t80_data->features & M41T80_FEATURE_SQ)
+		m41t80_sqw_register_clk(m41t80_data);
+#endif
+
+	rc = rtc_register_device(m41t80_data->rtc);
+	if (rc)
+		return rc;
+
+	return 0;
+}
+
+static int m41t80_remove(struct i2c_client *client)
+{
+#ifdef CONFIG_RTC_DRV_M41T80_WDT
+	struct m41t80_data *clientdata = i2c_get_clientdata(client);
+
+	if (clientdata->features & M41T80_FEATURE_HT) {
+		misc_deregister(&wdt_dev);
+		unregister_reboot_notifier(&wdt_notifier);
+	}
+#endif
+
+	return 0;
+}
+
+static struct i2c_driver m41t80_driver = {
+	.driver = {
+		.name = "rtc-m41t80",
+		.of_match_table = of_match_ptr(m41t80_of_match),
+		.pm = &m41t80_pm,
+	},
+	.probe = m41t80_probe,
+	.remove = m41t80_remove,
+	.id_table = m41t80_id,
+};
+
+module_i2c_driver(m41t80_driver);
+
+MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
+MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
+MODULE_LICENSE("GPL");