/*
   *  drivers/rtc/rtc-pcf8583.c
   *
   *  Copyright (C) 2000 Russell King

   *  Copyright (C) 2008 Wolfram Sang & Juergen Beisert, Pengutronix

   *
   * 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.
   *
   *  Driver for PCF8583 RTC & RAM chip
   *
   *  Converted to the generic RTC susbsystem by G. Liakhovetski (2006)
   */
  #include <linux/module.h>
  #include <linux/i2c.h>
  #include <linux/slab.h>

  #include <linux/rtc.h>

  #include <linux/init.h>
  #include <linux/errno.h>
  #include <linux/bcd.h>
  
  struct rtc_mem {
  	unsigned int	loc;
  	unsigned int	nr;
  	unsigned char	*data;
  };
  
  struct pcf8583 {

  	struct rtc_device *rtc;
  	unsigned char ctrl;
  };
  
  #define CTRL_STOP	0x80
  #define CTRL_HOLD	0x40
  #define CTRL_32KHZ	0x00
  #define CTRL_MASK	0x08
  #define CTRL_ALARMEN	0x04
  #define CTRL_ALARM	0x02
  #define CTRL_TIMER	0x01

  
  static struct i2c_driver pcf8583_driver;
  
  #define get_ctrl(x)    ((struct pcf8583 *)i2c_get_clientdata(x))->ctrl
  #define set_ctrl(x, v) get_ctrl(x) = v
  
  #define CMOS_YEAR	(64 + 128)
  #define CMOS_CHECKSUM	(63)
  
  static int pcf8583_get_datetime(struct i2c_client *client, struct rtc_time *dt)
  {
  	unsigned char buf[8], addr[1] = { 1 };
  	struct i2c_msg msgs[2] = {
  		{
  			.addr = client->addr,
  			.flags = 0,
  			.len = 1,
  			.buf = addr,
  		}, {
  			.addr = client->addr,
  			.flags = I2C_M_RD,
  			.len = 6,
  			.buf = buf,
  		}
  	};
  	int ret;
  
  	memset(buf, 0, sizeof(buf));
  
  	ret = i2c_transfer(client->adapter, msgs, 2);
  	if (ret == 2) {
  		dt->tm_year = buf[4] >> 6;
  		dt->tm_wday = buf[5] >> 5;
  
  		buf[4] &= 0x3f;
  		buf[5] &= 0x1f;

  		dt->tm_sec = bcd2bin(buf[1]);
  		dt->tm_min = bcd2bin(buf[2]);
  		dt->tm_hour = bcd2bin(buf[3]);
  		dt->tm_mday = bcd2bin(buf[4]);
  		dt->tm_mon = bcd2bin(buf[5]) - 1;

  	}
  
  	return ret == 2 ? 0 : -EIO;
  }
  
  static int pcf8583_set_datetime(struct i2c_client *client, struct rtc_time *dt, int datetoo)
  {
  	unsigned char buf[8];
  	int ret, len = 6;
  
  	buf[0] = 0;
  	buf[1] = get_ctrl(client) | 0x80;
  	buf[2] = 0;

  	buf[3] = bin2bcd(dt->tm_sec);
  	buf[4] = bin2bcd(dt->tm_min);
  	buf[5] = bin2bcd(dt->tm_hour);

  
  	if (datetoo) {
  		len = 8;

  		buf[6] = bin2bcd(dt->tm_mday) | (dt->tm_year << 6);
  		buf[7] = bin2bcd(dt->tm_mon + 1)  | (dt->tm_wday << 5);

  	}
  
  	ret = i2c_master_send(client, (char *)buf, len);
  	if (ret != len)
  		return -EIO;
  
  	buf[1] = get_ctrl(client);
  	ret = i2c_master_send(client, (char *)buf, 2);
  
  	return ret == 2 ? 0 : -EIO;
  }
  
  static int pcf8583_get_ctrl(struct i2c_client *client, unsigned char *ctrl)
  {
  	*ctrl = get_ctrl(client);
  	return 0;
  }
  
  static int pcf8583_set_ctrl(struct i2c_client *client, unsigned char *ctrl)
  {
  	unsigned char buf[2];
  
  	buf[0] = 0;
  	buf[1] = *ctrl;
  	set_ctrl(client, *ctrl);
  
  	return i2c_master_send(client, (char *)buf, 2);
  }
  
  static int pcf8583_read_mem(struct i2c_client *client, struct rtc_mem *mem)
  {
  	unsigned char addr[1];
  	struct i2c_msg msgs[2] = {
  		{
  			.addr = client->addr,
  			.flags = 0,
  			.len = 1,
  			.buf = addr,
  		}, {
  			.addr = client->addr,
  			.flags = I2C_M_RD,
  			.len = mem->nr,
  			.buf = mem->data,
  		}
  	};
  
  	if (mem->loc < 8)
  		return -EINVAL;
  
  	addr[0] = mem->loc;
  
  	return i2c_transfer(client->adapter, msgs, 2) == 2 ? 0 : -EIO;
  }
  
  static int pcf8583_write_mem(struct i2c_client *client, struct rtc_mem *mem)
  {

  	unsigned char buf[9];
  	int ret;

  	if (mem->loc < 8 || mem->nr > 8)

  		return -EINVAL;

  	buf[0] = mem->loc;
  	memcpy(buf + 1, mem->data, mem->nr);

  	ret = i2c_master_send(client, buf, mem->nr + 1);
  	return ret == mem->nr + 1 ? 0 : -EIO;

  }
  
  static int pcf8583_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	unsigned char ctrl, year[2];
  	struct rtc_mem mem = { CMOS_YEAR, sizeof(year), year };
  	int real_year, year_offset, err;
  
  	/*
  	 * Ensure that the RTC is running.
  	 */
  	pcf8583_get_ctrl(client, &ctrl);
  	if (ctrl & (CTRL_STOP | CTRL_HOLD)) {
  		unsigned char new_ctrl = ctrl & ~(CTRL_STOP | CTRL_HOLD);
  
  		printk(KERN_WARNING "RTC: resetting control %02x -> %02x
  ",
  		       ctrl, new_ctrl);
  
  		if ((err = pcf8583_set_ctrl(client, &new_ctrl)) < 0)
  			return err;
  	}
  
  	if (pcf8583_get_datetime(client, tm) ||
  	    pcf8583_read_mem(client, &mem))
  		return -EIO;
  
  	real_year = year[0];
  
  	/*
  	 * The RTC year holds the LSB two bits of the current
  	 * year, which should reflect the LSB two bits of the
  	 * CMOS copy of the year.  Any difference indicates
  	 * that we have to correct the CMOS version.
  	 */
  	year_offset = tm->tm_year - (real_year & 3);
  	if (year_offset < 0)
  		/*
  		 * RTC year wrapped.  Adjust it appropriately.
  		 */
  		year_offset += 4;

  	tm->tm_year = (real_year + year_offset + year[1] * 100) - 1900;

  
  	return 0;
  }
  
  static int pcf8583_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	unsigned char year[2], chk;
  	struct rtc_mem cmos_year  = { CMOS_YEAR, sizeof(year), year };
  	struct rtc_mem cmos_check = { CMOS_CHECKSUM, 1, &chk };

  	unsigned int proper_year = tm->tm_year + 1900;

  	int ret;
  
  	/*
  	 * The RTC's own 2-bit year must reflect the least
  	 * significant two bits of the CMOS year.
  	 */
  
  	ret = pcf8583_set_datetime(client, tm, 1);
  	if (ret)
  		return ret;
  
  	ret = pcf8583_read_mem(client, &cmos_check);
  	if (ret)
  		return ret;
  
  	ret = pcf8583_read_mem(client, &cmos_year);
  	if (ret)
  		return ret;
  
  	chk -= year[1] + year[0];

  	year[1] = proper_year / 100;
  	year[0] = proper_year % 100;

  
  	chk += year[1] + year[0];
  
  	ret = pcf8583_write_mem(client, &cmos_year);
  
  	if (ret)
  		return ret;
  
  	ret = pcf8583_write_mem(client, &cmos_check);
  
  	return ret;
  }

  static const struct rtc_class_ops pcf8583_rtc_ops = {

  	.read_time	= pcf8583_rtc_read_time,
  	.set_time	= pcf8583_rtc_set_time,
  };

  static int pcf8583_probe(struct i2c_client *client,
  				const struct i2c_device_id *id)

  {

  	struct pcf8583 *pcf8583;

  	int err;

  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
  		return -ENODEV;

  	pcf8583 = kzalloc(sizeof(struct pcf8583), GFP_KERNEL);
  	if (!pcf8583)

  		return -ENOMEM;

  	i2c_set_clientdata(client, pcf8583);

  	pcf8583->rtc = rtc_device_register(pcf8583_driver.driver.name,
  			&client->dev, &pcf8583_rtc_ops, THIS_MODULE);

  	if (IS_ERR(pcf8583->rtc)) {
  		err = PTR_ERR(pcf8583->rtc);

  		goto exit_kfree;
  	}

  	return 0;

  exit_kfree:
  	kfree(pcf8583);
  	return err;
  }

  static int __devexit pcf8583_remove(struct i2c_client *client)
  {
  	struct pcf8583 *pcf8583 = i2c_get_clientdata(client);

  	if (pcf8583->rtc)
  		rtc_device_unregister(pcf8583->rtc);
  	kfree(pcf8583);

  	return 0;

  }

  static const struct i2c_device_id pcf8583_id[] = {
  	{ "pcf8583", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, pcf8583_id);

  static struct i2c_driver pcf8583_driver = {
  	.driver = {
  		.name	= "pcf8583",
  		.owner	= THIS_MODULE,
  	},
  	.probe		= pcf8583_probe,
  	.remove		= __devexit_p(pcf8583_remove),
  	.id_table	= pcf8583_id,
  };

  
  static __init int pcf8583_init(void)
  {
  	return i2c_add_driver(&pcf8583_driver);
  }
  
  static __exit void pcf8583_exit(void)
  {
  	i2c_del_driver(&pcf8583_driver);
  }
  
  module_init(pcf8583_init);
  module_exit(pcf8583_exit);
  
  MODULE_AUTHOR("Russell King");
  MODULE_DESCRIPTION("PCF8583 I2C RTC driver");
  MODULE_LICENSE("GPL");