/*
   * An I2C driver for the Intersil ISL 12022
   *
   * Author: Roman Fietze <roman.fietze@telemotive.de>
   *
   * Based on the Philips PCF8563 RTC
   * by Alessandro Zummo <a.zummo@towertech.it>.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License version
   * 2 as published by the Free Software Foundation.
   */
  
  #include <linux/i2c.h>
  #include <linux/bcd.h>
  #include <linux/rtc.h>
  #include <linux/slab.h>
  #include <linux/module.h>
  #include <linux/err.h>
  
  #define DRV_VERSION "0.1"
  
  /* ISL register offsets */
  #define ISL12022_REG_SC		0x00
  #define ISL12022_REG_MN		0x01
  #define ISL12022_REG_HR		0x02
  #define ISL12022_REG_DT		0x03
  #define ISL12022_REG_MO		0x04
  #define ISL12022_REG_YR		0x05
  #define ISL12022_REG_DW		0x06
  
  #define ISL12022_REG_SR		0x07
  #define ISL12022_REG_INT	0x08
  
  /* ISL register bits */
  #define ISL12022_HR_MIL		(1 << 7)	/* military or 24 hour time */
  
  #define ISL12022_SR_LBAT85	(1 << 2)
  #define ISL12022_SR_LBAT75	(1 << 1)
  
  #define ISL12022_INT_WRTC	(1 << 6)
  
  
  static struct i2c_driver isl12022_driver;
  
  struct isl12022 {
  	struct rtc_device *rtc;
  
  	bool write_enabled;	/* true if write enable is set */
  };
  
  
  static int isl12022_read_regs(struct i2c_client *client, uint8_t reg,
  			      uint8_t *data, size_t n)
  {
  	struct i2c_msg msgs[] = {
  		{
  			.addr	= client->addr,
  			.flags	= 0,
  			.len	= 1,
  			.buf	= data
  		},		/* setup read ptr */
  		{
  			.addr	= client->addr,
  			.flags	= I2C_M_RD,
  			.len	= n,
  			.buf	= data
  		}
  	};
  
  	int ret;
  
  	data[0] = reg;
  	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
  	if (ret != ARRAY_SIZE(msgs)) {
  		dev_err(&client->dev, "%s: read error, ret=%d
  ",
  			__func__, ret);
  		return -EIO;
  	}
  
  	return 0;
  }
  
  
  static int isl12022_write_reg(struct i2c_client *client,
  			      uint8_t reg, uint8_t val)
  {
  	uint8_t data[2] = { reg, val };
  	int err;
  
  	err = i2c_master_send(client, data, sizeof(data));
  	if (err != sizeof(data)) {
  		dev_err(&client->dev,
  			"%s: err=%d addr=%02x, data=%02x
  ",
  			__func__, err, data[0], data[1]);
  		return -EIO;
  	}
  
  	return 0;
  }
  
  
  /*
   * In the routines that deal directly with the isl12022 hardware, we use
   * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
   */
  static int isl12022_get_datetime(struct i2c_client *client, struct rtc_time *tm)
  {
  	uint8_t buf[ISL12022_REG_INT + 1];
  	int ret;
  
  	ret = isl12022_read_regs(client, ISL12022_REG_SC, buf, sizeof(buf));
  	if (ret)
  		return ret;
  
  	if (buf[ISL12022_REG_SR] & (ISL12022_SR_LBAT85 | ISL12022_SR_LBAT75)) {
  		dev_warn(&client->dev,
  			 "voltage dropped below %u%%, "
  			 "date and time is not reliable.
  ",
  			 buf[ISL12022_REG_SR] & ISL12022_SR_LBAT85 ? 85 : 75);
  	}
  
  	dev_dbg(&client->dev,
  		"%s: raw data is sec=%02x, min=%02x, hr=%02x, "
  		"mday=%02x, mon=%02x, year=%02x, wday=%02x, "
  		"sr=%02x, int=%02x",
  		__func__,
  		buf[ISL12022_REG_SC],
  		buf[ISL12022_REG_MN],
  		buf[ISL12022_REG_HR],
  		buf[ISL12022_REG_DT],
  		buf[ISL12022_REG_MO],
  		buf[ISL12022_REG_YR],
  		buf[ISL12022_REG_DW],
  		buf[ISL12022_REG_SR],
  		buf[ISL12022_REG_INT]);
  
  	tm->tm_sec = bcd2bin(buf[ISL12022_REG_SC] & 0x7F);
  	tm->tm_min = bcd2bin(buf[ISL12022_REG_MN] & 0x7F);
  	tm->tm_hour = bcd2bin(buf[ISL12022_REG_HR] & 0x3F);
  	tm->tm_mday = bcd2bin(buf[ISL12022_REG_DT] & 0x3F);
  	tm->tm_wday = buf[ISL12022_REG_DW] & 0x07;
  	tm->tm_mon = bcd2bin(buf[ISL12022_REG_MO] & 0x1F) - 1;
  	tm->tm_year = bcd2bin(buf[ISL12022_REG_YR]) + 100;
  
  	dev_dbg(&client->dev, "%s: 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);
  
  	/* The clock can give out invalid datetime, but we cannot return
  	 * -EINVAL otherwise hwclock will refuse to set the time on bootup. */
  	if (rtc_valid_tm(tm) < 0)
  		dev_err(&client->dev, "retrieved date and time is invalid.
  ");
  
  	return 0;
  }
  
  static int isl12022_set_datetime(struct i2c_client *client, struct rtc_time *tm)
  {
  	struct isl12022 *isl12022 = i2c_get_clientdata(client);
  	size_t i;
  	int ret;
  	uint8_t buf[ISL12022_REG_DW + 1];
  
  	dev_dbg(&client->dev, "%s: 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);
  
  	if (!isl12022->write_enabled) {
  
  		ret = isl12022_read_regs(client, ISL12022_REG_INT, buf, 1);
  		if (ret)
  			return ret;
  
  		/* Check if WRTC (write rtc enable) is set factory default is
  		 * 0 (not set) */
  		if (!(buf[0] & ISL12022_INT_WRTC)) {
  			dev_info(&client->dev,
  				 "init write enable and 24 hour format
  ");
  
  			/* Set the write enable bit. */
  			ret = isl12022_write_reg(client,
  						 ISL12022_REG_INT,
  						 buf[0] | ISL12022_INT_WRTC);
  			if (ret)
  				return ret;
  
  			/* Write to any RTC register to start RTC, we use the
  			 * HR register, setting the MIL bit to use the 24 hour
  			 * format. */
  			ret = isl12022_read_regs(client, ISL12022_REG_HR,
  						 buf, 1);
  			if (ret)
  				return ret;
  
  			ret = isl12022_write_reg(client,
  						 ISL12022_REG_HR,
  						 buf[0] | ISL12022_HR_MIL);
  			if (ret)
  				return ret;
  		}
  
  		isl12022->write_enabled = 1;
  	}
  
  	/* hours, minutes and seconds */
  	buf[ISL12022_REG_SC] = bin2bcd(tm->tm_sec);
  	buf[ISL12022_REG_MN] = bin2bcd(tm->tm_min);
  	buf[ISL12022_REG_HR] = bin2bcd(tm->tm_hour) | ISL12022_HR_MIL;
  
  	buf[ISL12022_REG_DT] = bin2bcd(tm->tm_mday);
  
  	/* month, 1 - 12 */
  	buf[ISL12022_REG_MO] = bin2bcd(tm->tm_mon + 1);
  
  	/* year and century */
  	buf[ISL12022_REG_YR] = bin2bcd(tm->tm_year % 100);
  
  	buf[ISL12022_REG_DW] = tm->tm_wday & 0x07;
  
  	/* write register's data */
  	for (i = 0; i < ARRAY_SIZE(buf); i++) {
  		ret = isl12022_write_reg(client, ISL12022_REG_SC + i,
  					 buf[ISL12022_REG_SC + i]);
  		if (ret)
  			return -EIO;
  	}
  
  	return 0;
  }
  
  static int isl12022_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	return isl12022_get_datetime(to_i2c_client(dev), tm);
  }
  
  static int isl12022_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {
  	return isl12022_set_datetime(to_i2c_client(dev), tm);
  }
  
  static const struct rtc_class_ops isl12022_rtc_ops = {
  	.read_time	= isl12022_rtc_read_time,
  	.set_time	= isl12022_rtc_set_time,
  };
  
  static int isl12022_probe(struct i2c_client *client,
  			  const struct i2c_device_id *id)
  {
  	struct isl12022 *isl12022;
  
  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
  		return -ENODEV;
  
  	isl12022 = devm_kzalloc(&client->dev, sizeof(struct isl12022),
  				GFP_KERNEL);
  	if (!isl12022)
  		return -ENOMEM;
  
  	dev_dbg(&client->dev, "chip found, driver version " DRV_VERSION "
  ");
  
  	i2c_set_clientdata(client, isl12022);
  
  	isl12022->rtc = devm_rtc_device_register(&client->dev,
  					isl12022_driver.driver.name,
  					&isl12022_rtc_ops, THIS_MODULE);
  	return PTR_ERR_OR_ZERO(isl12022->rtc);
  }
  
  static const struct i2c_device_id isl12022_id[] = {
  	{ "isl12022", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, isl12022_id);
  
  static struct i2c_driver isl12022_driver = {
  	.driver		= {
  		.name	= "rtc-isl12022",
  	},
  	.probe		= isl12022_probe,
  	.id_table	= isl12022_id,
  };
  
  module_i2c_driver(isl12022_driver);
  
  MODULE_AUTHOR("roman.fietze@telemotive.de");
  MODULE_DESCRIPTION("ISL 12022 RTC driver");
  MODULE_LICENSE("GPL");
  MODULE_VERSION(DRV_VERSION);