/*
   * 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>
  
  #define S35390A_CMD_STATUS1	0
  #define S35390A_CMD_STATUS2	1
  #define S35390A_CMD_TIME1	2
  
  #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_FLAG_POC	0x01
  #define S35390A_FLAG_BLD	0x02
  #define S35390A_FLAG_24H	0x40
  #define S35390A_FLAG_RESET	0x80
  #define S35390A_FLAG_TEST	0x01

  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[] = {
  		{ client->addr, 0, len, 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[] = {
  		{ client->addr, I2C_M_RD, len, buf },
  	};
  
  	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
  		return -EIO;
  
  	return 0;
  }
  
  static int s35390a_reset(struct s35390a *s35390a)
  {
  	char buf[1];
  
  	if (s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, buf, sizeof(buf)) < 0)
  		return -EIO;
  
  	if (!(buf[0] & (S35390A_FLAG_POC | S35390A_FLAG_BLD)))
  		return 0;
  
  	buf[0] |= (S35390A_FLAG_RESET | S35390A_FLAG_24H);
  	buf[0] &= 0xf0;
  	return s35390a_set_reg(s35390a, S35390A_CMD_STATUS1, buf, sizeof(buf));
  }
  
  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_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,
  };
  
  static struct i2c_driver s35390a_driver;

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

  {
  	int err;
  	unsigned int i;
  	struct s35390a *s35390a;
  	struct rtc_time tm;
  	char buf[1];
  
  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
  		err = -ENODEV;
  		goto exit;
  	}
  
  	s35390a = kzalloc(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 = s35390a_reset(s35390a);
  	if (err < 0) {
  		dev_err(&client->dev, "error resetting chip
  ");
  		goto exit_dummy;
  	}
  
  	err = s35390a_disable_test_mode(s35390a);
  	if (err < 0) {
  		dev_err(&client->dev, "error disabling test mode
  ");
  		goto exit_dummy;
  	}
  
  	err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, buf, sizeof(buf));
  	if (err < 0) {
  		dev_err(&client->dev, "error checking 12/24 hour mode
  ");
  		goto exit_dummy;
  	}
  	if (buf[0] & S35390A_FLAG_24H)
  		s35390a->twentyfourhour = 1;
  	else
  		s35390a->twentyfourhour = 0;
  
  	if (s35390a_get_datetime(client, &tm) < 0)
  		dev_warn(&client->dev, "clock needs to be set
  ");
  
  	s35390a->rtc = rtc_device_register(s35390a_driver.driver.name,
  				&client->dev, &s35390a_rtc_ops, THIS_MODULE);
  
  	if (IS_ERR(s35390a->rtc)) {
  		err = PTR_ERR(s35390a->rtc);
  		goto exit_dummy;
  	}
  	return 0;
  
  exit_dummy:
  	for (i = 1; i < 8; ++i)
  		if (s35390a->client[i])
  			i2c_unregister_device(s35390a->client[i]);
  	kfree(s35390a);

  
  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]);
  
  	rtc_device_unregister(s35390a->rtc);
  	kfree(s35390a);

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

  	.id_table	= s35390a_id,

  };
  
  static int __init s35390a_rtc_init(void)
  {
  	return i2c_add_driver(&s35390a_driver);
  }
  
  static void __exit s35390a_rtc_exit(void)
  {
  	i2c_del_driver(&s35390a_driver);
  }
  
  MODULE_AUTHOR("Byron Bradley <byron.bbradley@gmail.com>");
  MODULE_DESCRIPTION("S35390A RTC driver");
  MODULE_LICENSE("GPL");
  
  module_init(s35390a_rtc_init);
  module_exit(s35390a_rtc_exit);