/*
   * Driver for Epson RTC-9701JE
   *
   * Copyright (C) 2008 Magnus Damm
   *
   * Based on rtc-max6902.c
   *
   * Copyright (C) 2006 8D Technologies inc.
   * Copyright (C) 2004 Compulab 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/module.h>
  #include <linux/kernel.h>
  #include <linux/platform_device.h>
  #include <linux/device.h>
  #include <linux/init.h>
  #include <linux/rtc.h>
  #include <linux/spi/spi.h>
  #include <linux/bcd.h>
  #include <linux/delay.h>
  #include <linux/bitops.h>
  
  #define RSECCNT	0x00	/* Second Counter */
  #define RMINCNT	0x01	/* Minute Counter */
  #define RHRCNT	0x02	/* Hour Counter */
  #define RWKCNT	0x03	/* Week Counter */
  #define RDAYCNT	0x04	/* Day Counter */
  #define RMONCNT	0x05	/* Month Counter */
  #define RYRCNT	0x06	/* Year Counter */
  #define R100CNT	0x07	/* Y100 Counter */
  #define RMINAR	0x08	/* Minute Alarm */
  #define RHRAR	0x09	/* Hour Alarm */
  #define RWKAR	0x0a	/* Week/Day Alarm */
  #define RTIMCNT	0x0c	/* Interval Timer */
  #define REXT	0x0d	/* Extension Register */
  #define RFLAG	0x0e	/* RTC Flag Register */
  #define RCR	0x0f	/* RTC Control Register */
  
  static int write_reg(struct device *dev, int address, unsigned char data)
  {
  	struct spi_device *spi = to_spi_device(dev);
  	unsigned char buf[2];
  
  	buf[0] = address & 0x7f;
  	buf[1] = data;
  
  	return spi_write(spi, buf, ARRAY_SIZE(buf));
  }
  
  static int read_regs(struct device *dev, unsigned char *regs, int no_regs)
  {
  	struct spi_device *spi = to_spi_device(dev);
  	u8 txbuf[1], rxbuf[1];
  	int k, ret;
  
  	ret = 0;
  
  	for (k = 0; ret == 0 && k < no_regs; k++) {
  		txbuf[0] = 0x80 | regs[k];
  		ret = spi_write_then_read(spi, txbuf, 1, rxbuf, 1);
  		regs[k] = rxbuf[0];
  	}
  
  	return ret;
  }
  
  static int r9701_get_datetime(struct device *dev, struct rtc_time *dt)
  {
  	int ret;
  	unsigned char buf[] = { RSECCNT, RMINCNT, RHRCNT,
  				RDAYCNT, RMONCNT, RYRCNT };
  
  	ret = read_regs(dev, buf, ARRAY_SIZE(buf));
  	if (ret)
  		return ret;
  
  	memset(dt, 0, sizeof(*dt));
  
  	dt->tm_sec = bcd2bin(buf[0]); /* RSECCNT */
  	dt->tm_min = bcd2bin(buf[1]); /* RMINCNT */
  	dt->tm_hour = bcd2bin(buf[2]); /* RHRCNT */
  
  	dt->tm_mday = bcd2bin(buf[3]); /* RDAYCNT */
  	dt->tm_mon = bcd2bin(buf[4]) - 1; /* RMONCNT */
  	dt->tm_year = bcd2bin(buf[5]) + 100; /* RYRCNT */
  
  	/* the rtc device may contain illegal values on power up
  	 * according to the data sheet. make sure they are valid.
  	 */
  
  	return rtc_valid_tm(dt);
  }
  
  static int r9701_set_datetime(struct device *dev, struct rtc_time *dt)
  {
  	int ret, year;
  
  	year = dt->tm_year + 1900;
  	if (year >= 2100 || year < 2000)
  		return -EINVAL;
  
  	ret = write_reg(dev, RHRCNT, bin2bcd(dt->tm_hour));
  	ret = ret ? ret : write_reg(dev, RMINCNT, bin2bcd(dt->tm_min));
  	ret = ret ? ret : write_reg(dev, RSECCNT, bin2bcd(dt->tm_sec));
  	ret = ret ? ret : write_reg(dev, RDAYCNT, bin2bcd(dt->tm_mday));
  	ret = ret ? ret : write_reg(dev, RMONCNT, bin2bcd(dt->tm_mon + 1));
  	ret = ret ? ret : write_reg(dev, RYRCNT, bin2bcd(dt->tm_year - 100));
  	ret = ret ? ret : write_reg(dev, RWKCNT, 1 << dt->tm_wday);
  
  	return ret;
  }
  
  static const struct rtc_class_ops r9701_rtc_ops = {
  	.read_time	= r9701_get_datetime,
  	.set_time	= r9701_set_datetime,
  };
  
  static int r9701_probe(struct spi_device *spi)
  {
  	struct rtc_device *rtc;
  	struct rtc_time dt;
  	unsigned char tmp;
  	int res;
  
  	tmp = R100CNT;
  	res = read_regs(&spi->dev, &tmp, 1);
  	if (res || tmp != 0x20) {
  		dev_err(&spi->dev, "cannot read RTC register
  ");
  		return -ENODEV;
  	}
  
  	/*
  	 * The device seems to be present. Now check if the registers
  	 * contain invalid values. If so, try to write a default date:
  	 * 2000/1/1 00:00:00
  	 */
  	if (r9701_get_datetime(&spi->dev, &dt)) {
  		dev_info(&spi->dev, "trying to repair invalid date/time
  ");
  		dt.tm_sec  = 0;
  		dt.tm_min  = 0;
  		dt.tm_hour = 0;
  		dt.tm_mday = 1;
  		dt.tm_mon  = 0;
  		dt.tm_year = 100;
  
  		if (r9701_set_datetime(&spi->dev, &dt) ||
  				r9701_get_datetime(&spi->dev, &dt)) {
  			dev_err(&spi->dev, "cannot repair RTC register
  ");
  			return -ENODEV;
  		}
  	}
  
  	rtc = devm_rtc_device_register(&spi->dev, "r9701",
  				&r9701_rtc_ops, THIS_MODULE);
  	if (IS_ERR(rtc))
  		return PTR_ERR(rtc);
  
  	spi_set_drvdata(spi, rtc);
  
  	return 0;
  }
  
  static int r9701_remove(struct spi_device *spi)
  {
  	return 0;
  }
  
  static struct spi_driver r9701_driver = {
  	.driver = {
  		.name	= "rtc-r9701",
  		.owner	= THIS_MODULE,
  	},
  	.probe	= r9701_probe,
  	.remove = r9701_remove,
  };
  
  module_spi_driver(r9701_driver);
  
  MODULE_DESCRIPTION("r9701 spi RTC driver");
  MODULE_AUTHOR("Magnus Damm <damm@opensource.se>");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("spi:rtc-r9701");