// 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.
  ");
  		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
  ");

  		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
  ");
  		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
  ");

  		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
  ",
  			   (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
  ", 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
  ");
  		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
  ");
  		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
  ");

  			wdt_disable();
  		}
  
  		if (rv & WDIOS_ENABLECARD) {

  			pr_info("enable watchdog
  ");

  			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
  ");

  		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
  ");
  			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!
  ");

  			dev_info(&client->dev, "Power Down at %ptR
  ", &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
  ");

  		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
  ");

  		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");