/*
   * Seiko Instruments S-35390A RTC Driver
   *
   * Copyright (c) 2007 Byron Bradley
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/rtc.h>
  #include <linux/i2c.h>
  #include <linux/bitrev.h>
  #include <linux/bcd.h>
  #include <linux/slab.h>

  #include <linux/delay.h>

  
  #define S35390A_CMD_STATUS1	0
  #define S35390A_CMD_STATUS2	1
  #define S35390A_CMD_TIME1	2

  #define S35390A_CMD_TIME2	3
  #define S35390A_CMD_INT2_REG1	5

  
  #define S35390A_BYTE_YEAR	0
  #define S35390A_BYTE_MONTH	1
  #define S35390A_BYTE_DAY	2
  #define S35390A_BYTE_WDAY	3
  #define S35390A_BYTE_HOURS	4
  #define S35390A_BYTE_MINS	5
  #define S35390A_BYTE_SECS	6

  #define S35390A_ALRM_BYTE_WDAY	0
  #define S35390A_ALRM_BYTE_HOURS	1
  #define S35390A_ALRM_BYTE_MINS	2

  /* flags for STATUS1 */

  #define S35390A_FLAG_POC	0x01
  #define S35390A_FLAG_BLD	0x02

  #define S35390A_FLAG_INT2	0x04

  #define S35390A_FLAG_24H	0x40
  #define S35390A_FLAG_RESET	0x80

  
  /* flag for STATUS2 */

  #define S35390A_FLAG_TEST	0x01

  #define S35390A_INT2_MODE_MASK		0xF0
  
  #define S35390A_INT2_MODE_NOINTR	0x00
  #define S35390A_INT2_MODE_FREQ		0x10
  #define S35390A_INT2_MODE_ALARM		0x40
  #define S35390A_INT2_MODE_PMIN_EDG	0x20

  static const struct i2c_device_id s35390a_id[] = {
  	{ "s35390a", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, s35390a_id);

  struct s35390a {
  	struct i2c_client *client[8];
  	struct rtc_device *rtc;
  	int twentyfourhour;
  };
  
  static int s35390a_set_reg(struct s35390a *s35390a, int reg, char *buf, int len)
  {
  	struct i2c_client *client = s35390a->client[reg];
  	struct i2c_msg msg[] = {

  		{
  			.addr = client->addr,
  			.len = len,
  			.buf = buf
  		},

  	};
  
  	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
  		return -EIO;
  
  	return 0;
  }
  
  static int s35390a_get_reg(struct s35390a *s35390a, int reg, char *buf, int len)
  {
  	struct i2c_client *client = s35390a->client[reg];
  	struct i2c_msg msg[] = {

  		{
  			.addr = client->addr,
  			.flags = I2C_M_RD,
  			.len = len,
  			.buf = buf
  		},

  	};
  
  	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
  		return -EIO;
  
  	return 0;
  }

  /*
   * Returns <0 on error, 0 if rtc is setup fine and 1 if the chip was reset.
   * To keep the information if an irq is pending, pass the value read from
   * STATUS1 to the caller.
   */
  static int s35390a_reset(struct s35390a *s35390a, char *status1)

  {

  	char buf;
  	int ret;
  	unsigned initcount = 0;

  	ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, status1, 1);
  	if (ret < 0)
  		return ret;

  	if (*status1 & S35390A_FLAG_POC)
  		/*
  		 * Do not communicate for 0.5 seconds since the power-on
  		 * detection circuit is in operation.
  		 */
  		msleep(500);
  	else if (!(*status1 & S35390A_FLAG_BLD))
  		/*
  		 * If both POC and BLD are unset everything is fine.
  		 */

  		return 0;

  	/*
  	 * At least one of POC and BLD are set, so reinitialise chip. Keeping
  	 * this information in the hardware to know later that the time isn't
  	 * valid is unfortunately not possible because POC and BLD are cleared
  	 * on read. So the reset is best done now.
  	 *
  	 * The 24H bit is kept over reset, so set it already here.
  	 */
  initialize:
  	*status1 = S35390A_FLAG_24H;
  	buf = S35390A_FLAG_RESET | S35390A_FLAG_24H;
  	ret = s35390a_set_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);
  
  	if (ret < 0)
  		return ret;
  
  	ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);
  	if (ret < 0)
  		return ret;
  
  	if (buf & (S35390A_FLAG_POC | S35390A_FLAG_BLD)) {
  		/* Try up to five times to reset the chip */
  		if (initcount < 5) {
  			++initcount;
  			goto initialize;
  		} else
  			return -EIO;
  	}
  
  	return 1;

  }
  
  static int s35390a_disable_test_mode(struct s35390a *s35390a)
  {
  	char buf[1];
  
  	if (s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf)) < 0)
  		return -EIO;
  
  	if (!(buf[0] & S35390A_FLAG_TEST))
  		return 0;
  
  	buf[0] &= ~S35390A_FLAG_TEST;
  	return s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf));
  }
  
  static char s35390a_hr2reg(struct s35390a *s35390a, int hour)
  {
  	if (s35390a->twentyfourhour)

  		return bin2bcd(hour);

  
  	if (hour < 12)

  		return bin2bcd(hour);

  	return 0x40 | bin2bcd(hour - 12);

  }
  
  static int s35390a_reg2hr(struct s35390a *s35390a, char reg)
  {
  	unsigned hour;
  
  	if (s35390a->twentyfourhour)

  		return bcd2bin(reg & 0x3f);

  	hour = bcd2bin(reg & 0x3f);

  	if (reg & 0x40)
  		hour += 12;
  
  	return hour;
  }
  
  static int s35390a_set_datetime(struct i2c_client *client, struct rtc_time *tm)
  {
  	struct s35390a	*s35390a = i2c_get_clientdata(client);
  	int i, err;
  	char buf[7];
  
  	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d mday=%d, "
  		"mon=%d, year=%d, wday=%d
  ", __func__, tm->tm_sec,
  		tm->tm_min, tm->tm_hour, tm->tm_mday, tm->tm_mon, tm->tm_year,
  		tm->tm_wday);

  	buf[S35390A_BYTE_YEAR] = bin2bcd(tm->tm_year - 100);
  	buf[S35390A_BYTE_MONTH] = bin2bcd(tm->tm_mon + 1);
  	buf[S35390A_BYTE_DAY] = bin2bcd(tm->tm_mday);
  	buf[S35390A_BYTE_WDAY] = bin2bcd(tm->tm_wday);

  	buf[S35390A_BYTE_HOURS] = s35390a_hr2reg(s35390a, tm->tm_hour);

  	buf[S35390A_BYTE_MINS] = bin2bcd(tm->tm_min);
  	buf[S35390A_BYTE_SECS] = bin2bcd(tm->tm_sec);

  
  	/* This chip expects the bits of each byte to be in reverse order */
  	for (i = 0; i < 7; ++i)
  		buf[i] = bitrev8(buf[i]);
  
  	err = s35390a_set_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
  
  	return err;
  }
  
  static int s35390a_get_datetime(struct i2c_client *client, struct rtc_time *tm)
  {
  	struct s35390a *s35390a = i2c_get_clientdata(client);
  	char buf[7];
  	int i, err;
  
  	err = s35390a_get_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
  	if (err < 0)
  		return err;
  
  	/* This chip returns the bits of each byte in reverse order */
  	for (i = 0; i < 7; ++i)
  		buf[i] = bitrev8(buf[i]);

  	tm->tm_sec = bcd2bin(buf[S35390A_BYTE_SECS]);
  	tm->tm_min = bcd2bin(buf[S35390A_BYTE_MINS]);

  	tm->tm_hour = s35390a_reg2hr(s35390a, buf[S35390A_BYTE_HOURS]);

  	tm->tm_wday = bcd2bin(buf[S35390A_BYTE_WDAY]);
  	tm->tm_mday = bcd2bin(buf[S35390A_BYTE_DAY]);
  	tm->tm_mon = bcd2bin(buf[S35390A_BYTE_MONTH]) - 1;
  	tm->tm_year = bcd2bin(buf[S35390A_BYTE_YEAR]) + 100;

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

  static int s35390a_set_alarm(struct i2c_client *client, struct rtc_wkalrm *alm)
  {
  	struct s35390a *s35390a = i2c_get_clientdata(client);
  	char buf[3], sts = 0;
  	int err, i;
  
  	dev_dbg(&client->dev, "%s: alm is secs=%d, mins=%d, hours=%d mday=%d, "\
  		"mon=%d, year=%d, wday=%d
  ", __func__, alm->time.tm_sec,
  		alm->time.tm_min, alm->time.tm_hour, alm->time.tm_mday,
  		alm->time.tm_mon, alm->time.tm_year, alm->time.tm_wday);

  	/* disable interrupt (which deasserts the irq line) */

  	err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
  	if (err < 0)
  		return err;

  	/* clear pending interrupt (in STATUS1 only), if any */

  	err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, &sts, sizeof(sts));
  	if (err < 0)
  		return err;
  
  	if (alm->enabled)
  		sts = S35390A_INT2_MODE_ALARM;
  	else
  		sts = S35390A_INT2_MODE_NOINTR;
  
  	/* This chip expects the bits of each byte to be in reverse order */
  	sts = bitrev8(sts);
  
  	/* set interupt mode*/
  	err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
  	if (err < 0)
  		return err;
  
  	if (alm->time.tm_wday != -1)
  		buf[S35390A_ALRM_BYTE_WDAY] = bin2bcd(alm->time.tm_wday) | 0x80;

  	else
  		buf[S35390A_ALRM_BYTE_WDAY] = 0;

  
  	buf[S35390A_ALRM_BYTE_HOURS] = s35390a_hr2reg(s35390a,
  			alm->time.tm_hour) | 0x80;
  	buf[S35390A_ALRM_BYTE_MINS] = bin2bcd(alm->time.tm_min) | 0x80;
  
  	if (alm->time.tm_hour >= 12)
  		buf[S35390A_ALRM_BYTE_HOURS] |= 0x40;
  
  	for (i = 0; i < 3; ++i)
  		buf[i] = bitrev8(buf[i]);
  
  	err = s35390a_set_reg(s35390a, S35390A_CMD_INT2_REG1, buf,
  								sizeof(buf));
  
  	return err;
  }
  
  static int s35390a_read_alarm(struct i2c_client *client, struct rtc_wkalrm *alm)
  {
  	struct s35390a *s35390a = i2c_get_clientdata(client);
  	char buf[3], sts;
  	int i, err;
  
  	err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
  	if (err < 0)
  		return err;

  	if ((bitrev8(sts) & S35390A_INT2_MODE_MASK) != S35390A_INT2_MODE_ALARM) {
  		/*
  		 * When the alarm isn't enabled, the register to configure
  		 * the alarm time isn't accessible.
  		 */
  		alm->enabled = 0;
  		return 0;
  	} else {
  		alm->enabled = 1;
  	}

  
  	err = s35390a_get_reg(s35390a, S35390A_CMD_INT2_REG1, buf, sizeof(buf));
  	if (err < 0)
  		return err;
  
  	/* This chip returns the bits of each byte in reverse order */

  	for (i = 0; i < 3; ++i)

  		buf[i] = bitrev8(buf[i]);

  	/*
  	 * B0 of the three matching registers is an enable flag. Iff it is set
  	 * the configured value is used for matching.
  	 */
  	if (buf[S35390A_ALRM_BYTE_WDAY] & 0x80)
  		alm->time.tm_wday =
  			bcd2bin(buf[S35390A_ALRM_BYTE_WDAY] & ~0x80);
  
  	if (buf[S35390A_ALRM_BYTE_HOURS] & 0x80)
  		alm->time.tm_hour =
  			s35390a_reg2hr(s35390a,
  				       buf[S35390A_ALRM_BYTE_HOURS] & ~0x80);
  
  	if (buf[S35390A_ALRM_BYTE_MINS] & 0x80)
  		alm->time.tm_min = bcd2bin(buf[S35390A_ALRM_BYTE_MINS] & ~0x80);
  
  	/* alarm triggers always at s=0 */
  	alm->time.tm_sec = 0;

  
  	dev_dbg(&client->dev, "%s: alm is mins=%d, hours=%d, wday=%d
  ",
  			__func__, alm->time.tm_min, alm->time.tm_hour,
  			alm->time.tm_wday);
  
  	return 0;
  }
  
  static int s35390a_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
  {
  	return s35390a_read_alarm(to_i2c_client(dev), alm);
  }
  
  static int s35390a_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
  {
  	return s35390a_set_alarm(to_i2c_client(dev), alm);
  }

  static int s35390a_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	return s35390a_get_datetime(to_i2c_client(dev), tm);
  }
  
  static int s35390a_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {
  	return s35390a_set_datetime(to_i2c_client(dev), tm);
  }
  
  static const struct rtc_class_ops s35390a_rtc_ops = {
  	.read_time	= s35390a_rtc_read_time,
  	.set_time	= s35390a_rtc_set_time,

  	.set_alarm	= s35390a_rtc_set_alarm,
  	.read_alarm	= s35390a_rtc_read_alarm,

  };
  
  static struct i2c_driver s35390a_driver;

  static int s35390a_probe(struct i2c_client *client,
  			 const struct i2c_device_id *id)

  {

  	int err, err_reset;

  	unsigned int i;
  	struct s35390a *s35390a;
  	struct rtc_time tm;

  	char buf, status1;

  
  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
  		err = -ENODEV;
  		goto exit;
  	}

  	s35390a = devm_kzalloc(&client->dev, sizeof(struct s35390a),
  				GFP_KERNEL);

  	if (!s35390a) {
  		err = -ENOMEM;
  		goto exit;
  	}
  
  	s35390a->client[0] = client;
  	i2c_set_clientdata(client, s35390a);
  
  	/* This chip uses multiple addresses, use dummy devices for them */
  	for (i = 1; i < 8; ++i) {
  		s35390a->client[i] = i2c_new_dummy(client->adapter,

  					client->addr + i);

  		if (!s35390a->client[i]) {
  			dev_err(&client->dev, "Address %02x unavailable
  ",
  						client->addr + i);
  			err = -EBUSY;
  			goto exit_dummy;
  		}
  	}

  	err_reset = s35390a_reset(s35390a, &status1);
  	if (err_reset < 0) {
  		err = err_reset;

  		dev_err(&client->dev, "error resetting chip
  ");
  		goto exit_dummy;
  	}

  	if (status1 & S35390A_FLAG_24H)

  		s35390a->twentyfourhour = 1;
  	else
  		s35390a->twentyfourhour = 0;

  	if (status1 & S35390A_FLAG_INT2) {
  		/* disable alarm (and maybe test mode) */
  		buf = 0;
  		err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &buf, 1);
  		if (err < 0) {
  			dev_err(&client->dev, "error disabling alarm");
  			goto exit_dummy;
  		}
  	} else {
  		err = s35390a_disable_test_mode(s35390a);
  		if (err < 0) {
  			dev_err(&client->dev, "error disabling test mode
  ");
  			goto exit_dummy;
  		}
  	}
  
  	if (err_reset > 0 || s35390a_get_datetime(client, &tm) < 0)

  		dev_warn(&client->dev, "clock needs to be set
  ");

  	device_set_wakeup_capable(&client->dev, 1);

  	s35390a->rtc = devm_rtc_device_register(&client->dev,
  					s35390a_driver.driver.name,
  					&s35390a_rtc_ops, THIS_MODULE);

  
  	if (IS_ERR(s35390a->rtc)) {
  		err = PTR_ERR(s35390a->rtc);
  		goto exit_dummy;
  	}

  
  	if (status1 & S35390A_FLAG_INT2)
  		rtc_update_irq(s35390a->rtc, 1, RTC_AF);

  	return 0;
  
  exit_dummy:
  	for (i = 1; i < 8; ++i)
  		if (s35390a->client[i])
  			i2c_unregister_device(s35390a->client[i]);

  
  exit:
  	return err;
  }
  
  static int s35390a_remove(struct i2c_client *client)
  {
  	unsigned int i;

  	struct s35390a *s35390a = i2c_get_clientdata(client);

  	for (i = 1; i < 8; ++i)
  		if (s35390a->client[i])
  			i2c_unregister_device(s35390a->client[i]);

  	return 0;
  }
  
  static struct i2c_driver s35390a_driver = {
  	.driver		= {
  		.name	= "rtc-s35390a",
  	},
  	.probe		= s35390a_probe,
  	.remove		= s35390a_remove,

  	.id_table	= s35390a_id,

  };

  module_i2c_driver(s35390a_driver);

  
  MODULE_AUTHOR("Byron Bradley <byron.bbradley@gmail.com>");
  MODULE_DESCRIPTION("S35390A RTC driver");
  MODULE_LICENSE("GPL");