/*
   * rtc-isl12057 - Driver for Intersil ISL12057 I2C Real Time Clock
   *
   * Copyright (C) 2013, Arnaud EBALARD <arno@natisbad.org>
   *
   * This work is largely based on Intersil ISL1208 driver developed by
   * Hebert Valerio Riedel <hvr@gnu.org>.
   *
   * Detailed datasheet on which this development is based is available here:
   *
   *  http://natisbad.org/NAS2/refs/ISL12057.pdf
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  #include <linux/module.h>
  #include <linux/mutex.h>
  #include <linux/rtc.h>
  #include <linux/i2c.h>
  #include <linux/bcd.h>
  #include <linux/rtc.h>
  #include <linux/of.h>
  #include <linux/of_device.h>
  #include <linux/regmap.h>
  
  #define DRV_NAME "rtc-isl12057"
  
  /* RTC section */
  #define ISL12057_REG_RTC_SC	0x00	/* Seconds */
  #define ISL12057_REG_RTC_MN	0x01	/* Minutes */
  #define ISL12057_REG_RTC_HR	0x02	/* Hours */
  #define ISL12057_REG_RTC_HR_PM	BIT(5)	/* AM/PM bit in 12h format */
  #define ISL12057_REG_RTC_HR_MIL BIT(6)	/* 24h/12h format */
  #define ISL12057_REG_RTC_DW	0x03	/* Day of the Week */
  #define ISL12057_REG_RTC_DT	0x04	/* Date */
  #define ISL12057_REG_RTC_MO	0x05	/* Month */
  #define ISL12057_REG_RTC_YR	0x06	/* Year */
  #define ISL12057_RTC_SEC_LEN	7
  
  /* Alarm 1 section */
  #define ISL12057_REG_A1_SC	0x07	/* Alarm 1 Seconds */
  #define ISL12057_REG_A1_MN	0x08	/* Alarm 1 Minutes */
  #define ISL12057_REG_A1_HR	0x09	/* Alarm 1 Hours */
  #define ISL12057_REG_A1_HR_PM	BIT(5)	/* AM/PM bit in 12h format */
  #define ISL12057_REG_A1_HR_MIL	BIT(6)	/* 24h/12h format */
  #define ISL12057_REG_A1_DWDT	0x0A	/* Alarm 1 Date / Day of the week */
  #define ISL12057_REG_A1_DWDT_B	BIT(6)	/* DW / DT selection bit */
  #define ISL12057_A1_SEC_LEN	4
  
  /* Alarm 2 section */
  #define ISL12057_REG_A2_MN	0x0B	/* Alarm 2 Minutes */
  #define ISL12057_REG_A2_HR	0x0C	/* Alarm 2 Hours */
  #define ISL12057_REG_A2_DWDT	0x0D	/* Alarm 2 Date / Day of the week */
  #define ISL12057_A2_SEC_LEN	3
  
  /* Control/Status registers */
  #define ISL12057_REG_INT	0x0E
  #define ISL12057_REG_INT_A1IE	BIT(0)	/* Alarm 1 interrupt enable bit */
  #define ISL12057_REG_INT_A2IE	BIT(1)	/* Alarm 2 interrupt enable bit */
  #define ISL12057_REG_INT_INTCN	BIT(2)	/* Interrupt control enable bit */
  #define ISL12057_REG_INT_RS1	BIT(3)	/* Freq out control bit 1 */
  #define ISL12057_REG_INT_RS2	BIT(4)	/* Freq out control bit 2 */
  #define ISL12057_REG_INT_EOSC	BIT(7)	/* Oscillator enable bit */
  
  #define ISL12057_REG_SR		0x0F
  #define ISL12057_REG_SR_A1F	BIT(0)	/* Alarm 1 interrupt bit */
  #define ISL12057_REG_SR_A2F	BIT(1)	/* Alarm 2 interrupt bit */
  #define ISL12057_REG_SR_OSF	BIT(7)	/* Oscillator failure bit */
  
  /* Register memory map length */
  #define ISL12057_MEM_MAP_LEN	0x10
  
  struct isl12057_rtc_data {
  	struct regmap *regmap;
  	struct mutex lock;
  };
  
  static void isl12057_rtc_regs_to_tm(struct rtc_time *tm, u8 *regs)
  {
  	tm->tm_sec = bcd2bin(regs[ISL12057_REG_RTC_SC]);
  	tm->tm_min = bcd2bin(regs[ISL12057_REG_RTC_MN]);
  
  	if (regs[ISL12057_REG_RTC_HR] & ISL12057_REG_RTC_HR_MIL) { /* AM/PM */
  		tm->tm_hour = bcd2bin(regs[ISL12057_REG_RTC_HR] & 0x0f);
  		if (regs[ISL12057_REG_RTC_HR] & ISL12057_REG_RTC_HR_PM)
  			tm->tm_hour += 12;
  	} else {					    /* 24 hour mode */
  		tm->tm_hour = bcd2bin(regs[ISL12057_REG_RTC_HR] & 0x3f);
  	}
  
  	tm->tm_mday = bcd2bin(regs[ISL12057_REG_RTC_DT]);
  	tm->tm_wday = bcd2bin(regs[ISL12057_REG_RTC_DW]) - 1; /* starts at 1 */
  	tm->tm_mon  = bcd2bin(regs[ISL12057_REG_RTC_MO]) - 1; /* starts at 1 */
  	tm->tm_year = bcd2bin(regs[ISL12057_REG_RTC_YR]) + 100;
  }
  
  static int isl12057_rtc_tm_to_regs(u8 *regs, struct rtc_time *tm)
  {
  	/*
  	 * The clock has an 8 bit wide bcd-coded register for the year.
  	 * tm_year is an offset from 1900 and we are interested in the
  	 * 2000-2099 range, so any value less than 100 is invalid.
  	 */
  	if (tm->tm_year < 100)
  		return -EINVAL;
  
  	regs[ISL12057_REG_RTC_SC] = bin2bcd(tm->tm_sec);
  	regs[ISL12057_REG_RTC_MN] = bin2bcd(tm->tm_min);
  	regs[ISL12057_REG_RTC_HR] = bin2bcd(tm->tm_hour); /* 24-hour format */
  	regs[ISL12057_REG_RTC_DT] = bin2bcd(tm->tm_mday);
  	regs[ISL12057_REG_RTC_MO] = bin2bcd(tm->tm_mon + 1);
  	regs[ISL12057_REG_RTC_YR] = bin2bcd(tm->tm_year - 100);
  	regs[ISL12057_REG_RTC_DW] = bin2bcd(tm->tm_wday + 1);
  
  	return 0;
  }
  
  /*
   * Try and match register bits w/ fixed null values to see whether we
   * are dealing with an ISL12057. Note: this function is called early
   * during init and hence does need mutex protection.
   */
  static int isl12057_i2c_validate_chip(struct regmap *regmap)
  {
  	u8 regs[ISL12057_MEM_MAP_LEN];
  	static const u8 mask[ISL12057_MEM_MAP_LEN] = { 0x80, 0x80, 0x80, 0xf8,
  						       0xc0, 0x60, 0x00, 0x00,
  						       0x00, 0x00, 0x00, 0x00,
  						       0x00, 0x00, 0x60, 0x7c };
  	int ret, i;
  
  	ret = regmap_bulk_read(regmap, 0, regs, ISL12057_MEM_MAP_LEN);
  	if (ret)
  		return ret;
  
  	for (i = 0; i < ISL12057_MEM_MAP_LEN; ++i) {
  		if (regs[i] & mask[i])	/* check if bits are cleared */
  			return -ENODEV;
  	}
  
  	return 0;
  }
  
  static int isl12057_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
  	u8 regs[ISL12057_RTC_SEC_LEN];
  	int ret;
  
  	mutex_lock(&data->lock);
  	ret = regmap_bulk_read(data->regmap, ISL12057_REG_RTC_SC, regs,
  			       ISL12057_RTC_SEC_LEN);
  	mutex_unlock(&data->lock);
  
  	if (ret) {
  		dev_err(dev, "%s: RTC read failed
  ", __func__);
  		return ret;
  	}
  
  	isl12057_rtc_regs_to_tm(tm, regs);
  
  	return rtc_valid_tm(tm);
  }
  
  static int isl12057_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {
  	struct isl12057_rtc_data *data = dev_get_drvdata(dev);
  	u8 regs[ISL12057_RTC_SEC_LEN];
  	int ret;
  
  	ret = isl12057_rtc_tm_to_regs(regs, tm);
  	if (ret)
  		return ret;
  
  	mutex_lock(&data->lock);
  	ret = regmap_bulk_write(data->regmap, ISL12057_REG_RTC_SC, regs,
  				ISL12057_RTC_SEC_LEN);
  	mutex_unlock(&data->lock);
  
  	if (ret)
  		dev_err(dev, "%s: RTC write failed
  ", __func__);
  
  	return ret;
  }
  
  /*
   * Check current RTC status and enable/disable what needs to be. Return 0 if
   * everything went ok and a negative value upon error. Note: this function
   * is called early during init and hence does need mutex protection.
   */
  static int isl12057_check_rtc_status(struct device *dev, struct regmap *regmap)
  {
  	int ret;
  
  	/* Enable oscillator if not already running */
  	ret = regmap_update_bits(regmap, ISL12057_REG_INT,
  				 ISL12057_REG_INT_EOSC, 0);
  	if (ret < 0) {
  		dev_err(dev, "Unable to enable oscillator
  ");
  		return ret;
  	}
  
  	/* Clear oscillator failure bit if needed */
  	ret = regmap_update_bits(regmap, ISL12057_REG_SR,
  				 ISL12057_REG_SR_OSF, 0);
  	if (ret < 0) {
  		dev_err(dev, "Unable to clear oscillator failure bit
  ");
  		return ret;
  	}
  
  	/* Clear alarm bit if needed */
  	ret = regmap_update_bits(regmap, ISL12057_REG_SR,
  				 ISL12057_REG_SR_A1F, 0);
  	if (ret < 0) {
  		dev_err(dev, "Unable to clear alarm bit
  ");
  		return ret;
  	}
  
  	return 0;
  }
  
  static const struct rtc_class_ops rtc_ops = {
  	.read_time = isl12057_rtc_read_time,
  	.set_time = isl12057_rtc_set_time,
  };
  
  static struct regmap_config isl12057_rtc_regmap_config = {
  	.reg_bits = 8,
  	.val_bits = 8,
  };
  
  static int isl12057_probe(struct i2c_client *client,
  			  const struct i2c_device_id *id)
  {
  	struct device *dev = &client->dev;
  	struct isl12057_rtc_data *data;
  	struct rtc_device *rtc;
  	struct regmap *regmap;
  	int ret;
  
  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
  				     I2C_FUNC_SMBUS_BYTE_DATA |
  				     I2C_FUNC_SMBUS_I2C_BLOCK))
  		return -ENODEV;
  
  	regmap = devm_regmap_init_i2c(client, &isl12057_rtc_regmap_config);
  	if (IS_ERR(regmap)) {
  		ret = PTR_ERR(regmap);
  		dev_err(dev, "regmap allocation failed: %d
  ", ret);
  		return ret;
  	}
  
  	ret = isl12057_i2c_validate_chip(regmap);
  	if (ret)
  		return ret;
  
  	ret = isl12057_check_rtc_status(dev, regmap);
  	if (ret)
  		return ret;
  
  	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  
  	mutex_init(&data->lock);
  	data->regmap = regmap;
  	dev_set_drvdata(dev, data);
  
  	rtc = devm_rtc_device_register(dev, DRV_NAME, &rtc_ops, THIS_MODULE);
  	if (IS_ERR(rtc))
  		return PTR_ERR(rtc);
  
  	return 0;
  }
  
  #ifdef CONFIG_OF
  static struct of_device_id isl12057_dt_match[] = {
  	{ .compatible = "isl,isl12057" },
  	{ },
  };
  #endif
  
  static const struct i2c_device_id isl12057_id[] = {
  	{ "isl12057", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, isl12057_id);
  
  static struct i2c_driver isl12057_driver = {
  	.driver = {
  		.name = DRV_NAME,
  		.owner = THIS_MODULE,
  		.of_match_table = of_match_ptr(isl12057_dt_match),
  	},
  	.probe	  = isl12057_probe,
  	.id_table = isl12057_id,
  };
  module_i2c_driver(isl12057_driver);
  
  MODULE_AUTHOR("Arnaud EBALARD <arno@natisbad.org>");
  MODULE_DESCRIPTION("Intersil ISL12057 RTC driver");
  MODULE_LICENSE("GPL");