/* rtc-ds3234.c
   *
   * Driver for Dallas Semiconductor (DS3234) SPI RTC with Integrated Crystal
   * and SRAM.
   *
   * Copyright (C) 2008 MIMOMax Wireless Ltd.
   *
   * 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/init.h>
  #include <linux/module.h>
  #include <linux/device.h>
  #include <linux/platform_device.h>
  #include <linux/rtc.h>
  #include <linux/spi/spi.h>
  #include <linux/bcd.h>
  
  #define DS3234_REG_SECONDS	0x00
  #define DS3234_REG_MINUTES	0x01
  #define DS3234_REG_HOURS	0x02
  #define DS3234_REG_DAY		0x03
  #define DS3234_REG_DATE		0x04
  #define DS3234_REG_MONTH	0x05
  #define DS3234_REG_YEAR		0x06
  #define DS3234_REG_CENTURY	(1 << 7) /* Bit 7 of the Month register */
  
  #define DS3234_REG_CONTROL	0x0E
  #define DS3234_REG_CONT_STAT	0x0F
  
  static int ds3234_set_reg(struct device *dev, unsigned char address,
  				unsigned char data)
  {
  	struct spi_device *spi = to_spi_device(dev);
  	unsigned char buf[2];
  
  	/* MSB must be '1' to indicate write */
  	buf[0] = address | 0x80;
  	buf[1] = data;
  
  	return spi_write_then_read(spi, buf, 2, NULL, 0);
  }
  
  static int ds3234_get_reg(struct device *dev, unsigned char address,
  				unsigned char *data)
  {
  	struct spi_device *spi = to_spi_device(dev);
  
  	*data = address & 0x7f;
  
  	return spi_write_then_read(spi, data, 1, data, 1);
  }
  
  static int ds3234_read_time(struct device *dev, struct rtc_time *dt)
  {
  	int err;
  	unsigned char buf[8];
  	struct spi_device *spi = to_spi_device(dev);
  
  	buf[0] = 0x00; /* Start address */
  
  	err = spi_write_then_read(spi, buf, 1, buf, 8);
  	if (err != 0)
  		return err;
  
  	/* Seconds, Minutes, Hours, Day, Date, Month, Year */
  	dt->tm_sec	= bcd2bin(buf[0]);
  	dt->tm_min	= bcd2bin(buf[1]);
  	dt->tm_hour	= bcd2bin(buf[2] & 0x3f);
  	dt->tm_wday	= bcd2bin(buf[3]) - 1; /* 0 = Sun */
  	dt->tm_mday	= bcd2bin(buf[4]);
  	dt->tm_mon	= bcd2bin(buf[5] & 0x1f) - 1; /* 0 = Jan */
  	dt->tm_year	= bcd2bin(buf[6] & 0xff) + 100; /* Assume 20YY */
  
  	return rtc_valid_tm(dt);
  }
  
  static int ds3234_set_time(struct device *dev, struct rtc_time *dt)
  {
  	ds3234_set_reg(dev, DS3234_REG_SECONDS, bin2bcd(dt->tm_sec));
  	ds3234_set_reg(dev, DS3234_REG_MINUTES, bin2bcd(dt->tm_min));
  	ds3234_set_reg(dev, DS3234_REG_HOURS, bin2bcd(dt->tm_hour) & 0x3f);
  
  	/* 0 = Sun */
  	ds3234_set_reg(dev, DS3234_REG_DAY, bin2bcd(dt->tm_wday + 1));
  	ds3234_set_reg(dev, DS3234_REG_DATE, bin2bcd(dt->tm_mday));
  
  	/* 0 = Jan */
  	ds3234_set_reg(dev, DS3234_REG_MONTH, bin2bcd(dt->tm_mon + 1));
  
  	/* Assume 20YY although we just want to make sure not to go negative. */
  	if (dt->tm_year > 100)
  		dt->tm_year -= 100;
  
  	ds3234_set_reg(dev, DS3234_REG_YEAR, bin2bcd(dt->tm_year));
  
  	return 0;
  }
  
  static const struct rtc_class_ops ds3234_rtc_ops = {
  	.read_time	= ds3234_read_time,
  	.set_time	= ds3234_set_time,
  };
  
  static int ds3234_probe(struct spi_device *spi)
  {
  	struct rtc_device *rtc;
  	unsigned char tmp;
  	int res;
  
  	spi->mode = SPI_MODE_3;
  	spi->bits_per_word = 8;
  	spi_setup(spi);
  
  	res = ds3234_get_reg(&spi->dev, DS3234_REG_SECONDS, &tmp);
  	if (res != 0)
  		return res;
  
  	/* Control settings
  	 *
  	 * CONTROL_REG
  	 * BIT 7	6	5	4	3	2	1	0
  	 *     EOSC	BBSQW	CONV	RS2	RS1	INTCN	A2IE	A1IE
  	 *
  	 *     0	0	0	1	1	1	0	0
  	 *
  	 * CONTROL_STAT_REG
  	 * BIT 7	6	5	4	3	2	1	0
  	 *     OSF	BB32kHz	CRATE1	CRATE0	EN32kHz	BSY	A2F	A1F
  	 *
  	 *     1	0	0	0	1	0	0	0
  	 */
  	ds3234_get_reg(&spi->dev, DS3234_REG_CONTROL, &tmp);
  	ds3234_set_reg(&spi->dev, DS3234_REG_CONTROL, tmp & 0x1c);
  
  	ds3234_get_reg(&spi->dev, DS3234_REG_CONT_STAT, &tmp);
  	ds3234_set_reg(&spi->dev, DS3234_REG_CONT_STAT, tmp & 0x88);
  
  	/* Print our settings */
  	ds3234_get_reg(&spi->dev, DS3234_REG_CONTROL, &tmp);
  	dev_info(&spi->dev, "Control Reg: 0x%02x
  ", tmp);
  
  	ds3234_get_reg(&spi->dev, DS3234_REG_CONT_STAT, &tmp);
  	dev_info(&spi->dev, "Ctrl/Stat Reg: 0x%02x
  ", tmp);
  
  	rtc = devm_rtc_device_register(&spi->dev, "ds3234",
  				&ds3234_rtc_ops, THIS_MODULE);
  	if (IS_ERR(rtc))
  		return PTR_ERR(rtc);
  
  	spi_set_drvdata(spi, rtc);
  
  	return 0;
  }
  
  static struct spi_driver ds3234_driver = {
  	.driver = {
  		.name	 = "ds3234",
  		.owner	= THIS_MODULE,
  	},
  	.probe	 = ds3234_probe,
  };
  
  module_spi_driver(ds3234_driver);
  
  MODULE_DESCRIPTION("DS3234 SPI RTC driver");
  MODULE_AUTHOR("Dennis Aberilla <denzzzhome@yahoo.com>");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("spi:ds3234");