/*

   * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC

   *
   * Copyright (C) 2008 Mercury IMC Ltd
   * Written by Mark Jackson <mpfj@mimc.co.uk>
   *
   * 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.
   *

   * NOTE: Currently this driver only supports the bare minimum for read
   * and write the RTC. The extra features provided by the chip family

   * (alarms, trickle charger, different control registers) are unavailable.
   */

  #include <linux/init.h>
  #include <linux/module.h>

  #include <linux/platform_device.h>
  #include <linux/rtc.h>
  #include <linux/spi/spi.h>
  #include <linux/bcd.h>

  #include <linux/slab.h>

  
  #define DS1390_REG_100THS		0x00
  #define DS1390_REG_SECONDS		0x01
  #define DS1390_REG_MINUTES		0x02
  #define DS1390_REG_HOURS		0x03
  #define DS1390_REG_DAY			0x04
  #define DS1390_REG_DATE			0x05
  #define DS1390_REG_MONTH_CENT		0x06
  #define DS1390_REG_YEAR			0x07
  
  #define DS1390_REG_ALARM_100THS		0x08
  #define DS1390_REG_ALARM_SECONDS	0x09
  #define DS1390_REG_ALARM_MINUTES	0x0A
  #define DS1390_REG_ALARM_HOURS		0x0B
  #define DS1390_REG_ALARM_DAY_DATE	0x0C
  
  #define DS1390_REG_CONTROL		0x0D
  #define DS1390_REG_STATUS		0x0E
  #define DS1390_REG_TRICKLE		0x0F
  
  struct ds1390 {
  	struct rtc_device *rtc;
  	u8 txrx_buf[9];	/* cmd + 8 registers */
  };

  static int ds1390_get_reg(struct device *dev, unsigned char address,
  				unsigned char *data)
  {
  	struct spi_device *spi = to_spi_device(dev);
  	struct ds1390 *chip = dev_get_drvdata(dev);
  	int status;
  
  	if (!data)
  		return -EINVAL;
  
  	/* Clear MSB to indicate read */
  	chip->txrx_buf[0] = address & 0x7f;
  	/* do the i/o */
  	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
  	if (status != 0)
  		return status;
  
  	*data = chip->txrx_buf[1];
  
  	return 0;
  }

  static int ds1390_read_time(struct device *dev, struct rtc_time *dt)

  {
  	struct spi_device *spi = to_spi_device(dev);
  	struct ds1390 *chip = dev_get_drvdata(dev);
  	int status;
  
  	/* build the message */
  	chip->txrx_buf[0] = DS1390_REG_SECONDS;
  
  	/* do the i/o */
  	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
  	if (status != 0)
  		return status;
  
  	/* The chip sends data in this order:
  	 * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
  	dt->tm_sec	= bcd2bin(chip->txrx_buf[0]);
  	dt->tm_min	= bcd2bin(chip->txrx_buf[1]);
  	dt->tm_hour	= bcd2bin(chip->txrx_buf[2]);
  	dt->tm_wday	= bcd2bin(chip->txrx_buf[3]);
  	dt->tm_mday	= bcd2bin(chip->txrx_buf[4]);
  	/* mask off century bit */
  	dt->tm_mon	= bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
  	/* adjust for century bit */
  	dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
  
  	return rtc_valid_tm(dt);
  }

  static int ds1390_set_time(struct device *dev, struct rtc_time *dt)

  {
  	struct spi_device *spi = to_spi_device(dev);
  	struct ds1390 *chip = dev_get_drvdata(dev);
  
  	/* build the message */
  	chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
  	chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
  	chip->txrx_buf[2] = bin2bcd(dt->tm_min);
  	chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
  	chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
  	chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
  	chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
  				((dt->tm_year > 99) ? 0x80 : 0x00);
  	chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
  
  	/* do the i/o */
  	return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
  }

  static const struct rtc_class_ops ds1390_rtc_ops = {
  	.read_time	= ds1390_read_time,
  	.set_time	= ds1390_set_time,
  };
  
  static int __devinit ds1390_probe(struct spi_device *spi)
  {

  	unsigned char tmp;
  	struct ds1390 *chip;
  	int res;

  	spi->mode = SPI_MODE_3;
  	spi->bits_per_word = 8;
  	spi_setup(spi);
  
  	chip = kzalloc(sizeof *chip, GFP_KERNEL);
  	if (!chip) {

  		dev_err(&spi->dev, "unable to allocate device memory
  ");

  		return -ENOMEM;
  	}

  	dev_set_drvdata(&spi->dev, chip);
  
  	res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);

  	if (res != 0) {
  		dev_err(&spi->dev, "unable to read device
  ");
  		kfree(chip);

  		return res;
  	}

  	chip->rtc = rtc_device_register("ds1390",
  				&spi->dev, &ds1390_rtc_ops, THIS_MODULE);
  	if (IS_ERR(chip->rtc)) {
  		dev_err(&spi->dev, "unable to register device
  ");
  		res = PTR_ERR(chip->rtc);
  		kfree(chip);
  	}
  
  	return res;

  }
  
  static int __devexit ds1390_remove(struct spi_device *spi)
  {

  	struct ds1390 *chip = spi_get_drvdata(spi);

  	rtc_device_unregister(chip->rtc);

  	kfree(chip);
  
  	return 0;
  }
  
  static struct spi_driver ds1390_driver = {
  	.driver = {
  		.name	= "rtc-ds1390",
  		.owner	= THIS_MODULE,
  	},
  	.probe	= ds1390_probe,
  	.remove = __devexit_p(ds1390_remove),
  };
  
  static __init int ds1390_init(void)
  {
  	return spi_register_driver(&ds1390_driver);
  }
  module_init(ds1390_init);
  
  static __exit void ds1390_exit(void)
  {
  	spi_unregister_driver(&ds1390_driver);
  }
  module_exit(ds1390_exit);

  MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");

  MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
  MODULE_LICENSE("GPL");

  MODULE_ALIAS("spi:rtc-ds1390");