/*
   * Driver for ST M41T94 SPI RTC
   *
   * Copyright (C) 2008 Kim B. Heino
   *
   * 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/module.h>
  #include <linux/kernel.h>
  #include <linux/platform_device.h>
  #include <linux/rtc.h>
  #include <linux/spi/spi.h>
  #include <linux/bcd.h>
  
  #define M41T94_REG_SECONDS	0x01
  #define M41T94_REG_MINUTES	0x02
  #define M41T94_REG_HOURS	0x03
  #define M41T94_REG_WDAY		0x04
  #define M41T94_REG_DAY		0x05
  #define M41T94_REG_MONTH	0x06
  #define M41T94_REG_YEAR		0x07
  #define M41T94_REG_HT		0x0c
  
  #define M41T94_BIT_HALT		0x40
  #define M41T94_BIT_STOP		0x80
  #define M41T94_BIT_CB		0x40
  #define M41T94_BIT_CEB		0x80
  
  static int m41t94_set_time(struct device *dev, struct rtc_time *tm)
  {
  	struct spi_device *spi = to_spi_device(dev);
  	u8 buf[8]; /* write cmd + 7 registers */
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d
  ",
  		"write", tm->tm_sec, tm->tm_min,
  		tm->tm_hour, tm->tm_mday,
  		tm->tm_mon, tm->tm_year, tm->tm_wday);
  
  	buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */

  	buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec);
  	buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min);
  	buf[M41T94_REG_HOURS]   = bin2bcd(tm->tm_hour);
  	buf[M41T94_REG_WDAY]    = bin2bcd(tm->tm_wday + 1);
  	buf[M41T94_REG_DAY]     = bin2bcd(tm->tm_mday);
  	buf[M41T94_REG_MONTH]   = bin2bcd(tm->tm_mon + 1);

  
  	buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB;
  	if (tm->tm_year >= 100)
  		buf[M41T94_REG_HOURS] |= M41T94_BIT_CB;

  	buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100);

  
  	return spi_write(spi, buf, 8);
  }
  
  static int m41t94_read_time(struct device *dev, struct rtc_time *tm)
  {
  	struct spi_device *spi = to_spi_device(dev);
  	u8 buf[2];
  	int ret, hour;
  
  	/* clear halt update bit */
  	ret = spi_w8r8(spi, M41T94_REG_HT);
  	if (ret < 0)
  		return ret;
  	if (ret & M41T94_BIT_HALT) {
  		buf[0] = 0x80 | M41T94_REG_HT;
  		buf[1] = ret & ~M41T94_BIT_HALT;
  		spi_write(spi, buf, 2);
  	}
  
  	/* clear stop bit */
  	ret = spi_w8r8(spi, M41T94_REG_SECONDS);
  	if (ret < 0)
  		return ret;
  	if (ret & M41T94_BIT_STOP) {
  		buf[0] = 0x80 | M41T94_REG_SECONDS;
  		buf[1] = ret & ~M41T94_BIT_STOP;
  		spi_write(spi, buf, 2);
  	}

  	tm->tm_sec  = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS));
  	tm->tm_min  = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES));

  	hour = spi_w8r8(spi, M41T94_REG_HOURS);

  	tm->tm_hour = bcd2bin(hour & 0x3f);
  	tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1;
  	tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY));
  	tm->tm_mon  = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1;
  	tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR));

  	if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB))
  		tm->tm_year += 100;
  
  	dev_dbg(dev, "%s secs=%d, mins=%d, "
  		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d
  ",
  		"read", tm->tm_sec, tm->tm_min,
  		tm->tm_hour, tm->tm_mday,
  		tm->tm_mon, tm->tm_year, tm->tm_wday);
  
  	/* initial clock setting can be undefined */
  	return rtc_valid_tm(tm);
  }
  
  static const struct rtc_class_ops m41t94_rtc_ops = {
  	.read_time	= m41t94_read_time,
  	.set_time	= m41t94_set_time,
  };
  
  static struct spi_driver m41t94_driver;

  static int m41t94_probe(struct spi_device *spi)

  {
  	struct rtc_device *rtc;
  	int res;
  
  	spi->bits_per_word = 8;
  	spi_setup(spi);
  
  	res = spi_w8r8(spi, M41T94_REG_SECONDS);
  	if (res < 0) {
  		dev_err(&spi->dev, "not found.
  ");
  		return res;
  	}

  	rtc = devm_rtc_device_register(&spi->dev, m41t94_driver.driver.name,
  					&m41t94_rtc_ops, THIS_MODULE);

  	if (IS_ERR(rtc))
  		return PTR_ERR(rtc);

  	spi_set_drvdata(spi, rtc);

  
  	return 0;
  }

  static struct spi_driver m41t94_driver = {
  	.driver = {
  		.name	= "rtc-m41t94",

  	},
  	.probe	= m41t94_probe,

  };

  module_spi_driver(m41t94_driver);

  
  MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
  MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
  MODULE_LICENSE("GPL");

  MODULE_ALIAS("spi:rtc-m41t94");