/*
   * RTC client/driver for the Maxim/Dallas DS3232 Real-Time Clock over I2C
   *
   * Copyright (C) 2009-2011 Freescale Semiconductor.
   * Author: Jack Lan <jack.lan@freescale.com>
   *
   * 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.
   */
  /*
   * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
   * recommened in .../Documentation/i2c/writing-clients section
   * "Sending and receiving", using SMBus level communication is preferred.
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/interrupt.h>
  #include <linux/i2c.h>
  #include <linux/rtc.h>
  #include <linux/bcd.h>
  #include <linux/workqueue.h>
  #include <linux/slab.h>
  
  #define DS3232_REG_SECONDS	0x00
  #define DS3232_REG_MINUTES	0x01
  #define DS3232_REG_HOURS	0x02
  #define DS3232_REG_AMPM		0x02
  #define DS3232_REG_DAY		0x03
  #define DS3232_REG_DATE		0x04
  #define DS3232_REG_MONTH	0x05
  #define DS3232_REG_CENTURY	0x05
  #define DS3232_REG_YEAR		0x06
  #define DS3232_REG_ALARM1         0x07	/* Alarm 1 BASE */
  #define DS3232_REG_ALARM2         0x0B	/* Alarm 2 BASE */
  #define DS3232_REG_CR		0x0E	/* Control register */
  #	define DS3232_REG_CR_nEOSC        0x80
  #       define DS3232_REG_CR_INTCN        0x04
  #       define DS3232_REG_CR_A2IE        0x02
  #       define DS3232_REG_CR_A1IE        0x01
  
  #define DS3232_REG_SR	0x0F	/* control/status register */
  #	define DS3232_REG_SR_OSF   0x80
  #       define DS3232_REG_SR_BSY   0x04
  #       define DS3232_REG_SR_A2F   0x02
  #       define DS3232_REG_SR_A1F   0x01
  
  struct ds3232 {
  	struct i2c_client *client;
  	struct rtc_device *rtc;
  	struct work_struct work;
  
  	/* The mutex protects alarm operations, and prevents a race
  	 * between the enable_irq() in the workqueue and the free_irq()
  	 * in the remove function.
  	 */
  	struct mutex mutex;
  	int exiting;
  };
  
  static struct i2c_driver ds3232_driver;
  
  static int ds3232_check_rtc_status(struct i2c_client *client)
  {
  	int ret = 0;
  	int control, stat;
  
  	stat = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
  	if (stat < 0)
  		return stat;
  
  	if (stat & DS3232_REG_SR_OSF)
  		dev_warn(&client->dev,
  				"oscillator discontinuity flagged, "
  				"time unreliable
  ");
  
  	stat &= ~(DS3232_REG_SR_OSF | DS3232_REG_SR_A1F | DS3232_REG_SR_A2F);
  
  	ret = i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
  	if (ret < 0)
  		return ret;
  
  	/* If the alarm is pending, clear it before requesting
  	 * the interrupt, so an interrupt event isn't reported
  	 * before everything is initialized.
  	 */
  
  	control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
  	if (control < 0)
  		return control;
  
  	control &= ~(DS3232_REG_CR_A1IE | DS3232_REG_CR_A2IE);
  	control |= DS3232_REG_CR_INTCN;
  
  	return i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
  }
  
  static int ds3232_read_time(struct device *dev, struct rtc_time *time)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	int ret;
  	u8 buf[7];
  	unsigned int year, month, day, hour, minute, second;
  	unsigned int week, twelve_hr, am_pm;
  	unsigned int century, add_century = 0;
  
  	ret = i2c_smbus_read_i2c_block_data(client, DS3232_REG_SECONDS, 7, buf);
  
  	if (ret < 0)
  		return ret;
  	if (ret < 7)
  		return -EIO;
  
  	second = buf[0];
  	minute = buf[1];
  	hour = buf[2];
  	week = buf[3];
  	day = buf[4];
  	month = buf[5];
  	year = buf[6];
  
  	/* Extract additional information for AM/PM and century */
  
  	twelve_hr = hour & 0x40;
  	am_pm = hour & 0x20;
  	century = month & 0x80;
  
  	/* Write to rtc_time structure */
  
  	time->tm_sec = bcd2bin(second);
  	time->tm_min = bcd2bin(minute);
  	if (twelve_hr) {
  		/* Convert to 24 hr */
  		if (am_pm)
  			time->tm_hour = bcd2bin(hour & 0x1F) + 12;
  		else
  			time->tm_hour = bcd2bin(hour & 0x1F);
  	} else {
  		time->tm_hour = bcd2bin(hour);
  	}
  
  	/* Day of the week in linux range is 0~6 while 1~7 in RTC chip */
  	time->tm_wday = bcd2bin(week) - 1;
  	time->tm_mday = bcd2bin(day);
  	/* linux tm_mon range:0~11, while month range is 1~12 in RTC chip */
  	time->tm_mon = bcd2bin(month & 0x7F) - 1;
  	if (century)
  		add_century = 100;
  
  	time->tm_year = bcd2bin(year) + add_century;
  
  	return rtc_valid_tm(time);
  }
  
  static int ds3232_set_time(struct device *dev, struct rtc_time *time)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	u8 buf[7];
  
  	/* Extract time from rtc_time and load into ds3232*/
  
  	buf[0] = bin2bcd(time->tm_sec);
  	buf[1] = bin2bcd(time->tm_min);
  	buf[2] = bin2bcd(time->tm_hour);
  	/* Day of the week in linux range is 0~6 while 1~7 in RTC chip */
  	buf[3] = bin2bcd(time->tm_wday + 1);
  	buf[4] = bin2bcd(time->tm_mday); /* Date */
  	/* linux tm_mon range:0~11, while month range is 1~12 in RTC chip */
  	buf[5] = bin2bcd(time->tm_mon + 1);
  	if (time->tm_year >= 100) {
  		buf[5] |= 0x80;
  		buf[6] = bin2bcd(time->tm_year - 100);
  	} else {
  		buf[6] = bin2bcd(time->tm_year);
  	}
  
  	return i2c_smbus_write_i2c_block_data(client,
  					      DS3232_REG_SECONDS, 7, buf);
  }
  
  /*
   * DS3232 has two alarm, we only use alarm1
   * According to linux specification, only support one-shot alarm
   * no periodic alarm mode
   */
  static int ds3232_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ds3232 *ds3232 = i2c_get_clientdata(client);
  	int control, stat;
  	int ret;
  	u8 buf[4];
  
  	mutex_lock(&ds3232->mutex);
  
  	ret = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
  	if (ret < 0)
  		goto out;
  	stat = ret;
  	ret = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
  	if (ret < 0)
  		goto out;
  	control = ret;
  	ret = i2c_smbus_read_i2c_block_data(client, DS3232_REG_ALARM1, 4, buf);
  	if (ret < 0)
  		goto out;
  
  	alarm->time.tm_sec = bcd2bin(buf[0] & 0x7F);
  	alarm->time.tm_min = bcd2bin(buf[1] & 0x7F);
  	alarm->time.tm_hour = bcd2bin(buf[2] & 0x7F);
  	alarm->time.tm_mday = bcd2bin(buf[3] & 0x7F);
  
  	alarm->time.tm_mon = -1;
  	alarm->time.tm_year = -1;
  	alarm->time.tm_wday = -1;
  	alarm->time.tm_yday = -1;
  	alarm->time.tm_isdst = -1;
  
  	alarm->enabled = !!(control & DS3232_REG_CR_A1IE);
  	alarm->pending = !!(stat & DS3232_REG_SR_A1F);
  
  	ret = 0;
  out:
  	mutex_unlock(&ds3232->mutex);
  	return ret;
  }
  
  /*
   * linux rtc-module does not support wday alarm
   * and only 24h time mode supported indeed
   */
  static int ds3232_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ds3232 *ds3232 = i2c_get_clientdata(client);
  	int control, stat;
  	int ret;
  	u8 buf[4];
  
  	if (client->irq <= 0)
  		return -EINVAL;
  
  	mutex_lock(&ds3232->mutex);
  
  	buf[0] = bin2bcd(alarm->time.tm_sec);
  	buf[1] = bin2bcd(alarm->time.tm_min);
  	buf[2] = bin2bcd(alarm->time.tm_hour);
  	buf[3] = bin2bcd(alarm->time.tm_mday);
  
  	/* clear alarm interrupt enable bit */
  	ret = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
  	if (ret < 0)
  		goto out;
  	control = ret;
  	control &= ~(DS3232_REG_CR_A1IE | DS3232_REG_CR_A2IE);
  	ret = i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
  	if (ret < 0)
  		goto out;
  
  	/* clear any pending alarm flag */
  	ret = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
  	if (ret < 0)
  		goto out;
  	stat = ret;
  	stat &= ~(DS3232_REG_SR_A1F | DS3232_REG_SR_A2F);
  	ret = i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
  	if (ret < 0)
  		goto out;
  
  	ret = i2c_smbus_write_i2c_block_data(client, DS3232_REG_ALARM1, 4, buf);
  
  	if (alarm->enabled) {
  		control |= DS3232_REG_CR_A1IE;
  		ret = i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
  	}
  out:
  	mutex_unlock(&ds3232->mutex);
  	return ret;
  }
  
  static void ds3232_update_alarm(struct i2c_client *client)
  {
  	struct ds3232 *ds3232 = i2c_get_clientdata(client);
  	int control;
  	int ret;
  	u8 buf[4];
  
  	mutex_lock(&ds3232->mutex);
  
  	ret = i2c_smbus_read_i2c_block_data(client, DS3232_REG_ALARM1, 4, buf);
  	if (ret < 0)
  		goto unlock;
  
  	buf[0] = bcd2bin(buf[0]) < 0 || (ds3232->rtc->irq_data & RTC_UF) ?
  								0x80 : buf[0];
  	buf[1] = bcd2bin(buf[1]) < 0 || (ds3232->rtc->irq_data & RTC_UF) ?
  								0x80 : buf[1];
  	buf[2] = bcd2bin(buf[2]) < 0 || (ds3232->rtc->irq_data & RTC_UF) ?
  								0x80 : buf[2];
  	buf[3] = bcd2bin(buf[3]) < 0 || (ds3232->rtc->irq_data & RTC_UF) ?
  								0x80 : buf[3];
  
  	ret = i2c_smbus_write_i2c_block_data(client, DS3232_REG_ALARM1, 4, buf);
  	if (ret < 0)
  		goto unlock;
  
  	control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
  	if (control < 0)
  		goto unlock;
  
  	if (ds3232->rtc->irq_data & (RTC_AF | RTC_UF))
  		/* enable alarm1 interrupt */
  		control |= DS3232_REG_CR_A1IE;
  	else
  		/* disable alarm1 interrupt */
  		control &= ~(DS3232_REG_CR_A1IE);
  	i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
  
  unlock:
  	mutex_unlock(&ds3232->mutex);
  }
  
  static int ds3232_alarm_irq_enable(struct device *dev, unsigned int enabled)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ds3232 *ds3232 = i2c_get_clientdata(client);
  
  	if (client->irq <= 0)
  		return -EINVAL;
  
  	if (enabled)
  		ds3232->rtc->irq_data |= RTC_AF;
  	else
  		ds3232->rtc->irq_data &= ~RTC_AF;
  
  	ds3232_update_alarm(client);
  	return 0;
  }
  
  static irqreturn_t ds3232_irq(int irq, void *dev_id)
  {
  	struct i2c_client *client = dev_id;
  	struct ds3232 *ds3232 = i2c_get_clientdata(client);
  
  	disable_irq_nosync(irq);
  	schedule_work(&ds3232->work);
  	return IRQ_HANDLED;
  }
  
  static void ds3232_work(struct work_struct *work)
  {
  	struct ds3232 *ds3232 = container_of(work, struct ds3232, work);
  	struct i2c_client *client = ds3232->client;
  	int stat, control;
  
  	mutex_lock(&ds3232->mutex);
  
  	stat = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
  	if (stat < 0)
  		goto unlock;
  
  	if (stat & DS3232_REG_SR_A1F) {
  		control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
  		if (control < 0)
  			goto out;
  		/* disable alarm1 interrupt */
  		control &= ~(DS3232_REG_CR_A1IE);
  		i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
  
  		/* clear the alarm pend flag */
  		stat &= ~DS3232_REG_SR_A1F;
  		i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
  
  		rtc_update_irq(ds3232->rtc, 1, RTC_AF | RTC_IRQF);
  	}
  
  out:
  	if (!ds3232->exiting)
  		enable_irq(client->irq);
  unlock:
  	mutex_unlock(&ds3232->mutex);
  }
  
  static const struct rtc_class_ops ds3232_rtc_ops = {
  	.read_time = ds3232_read_time,
  	.set_time = ds3232_set_time,
  	.read_alarm = ds3232_read_alarm,
  	.set_alarm = ds3232_set_alarm,
  	.alarm_irq_enable = ds3232_alarm_irq_enable,
  };
  
  static int ds3232_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)
  {
  	struct ds3232 *ds3232;
  	int ret;
  
  	ds3232 = devm_kzalloc(&client->dev, sizeof(struct ds3232), GFP_KERNEL);
  	if (!ds3232)
  		return -ENOMEM;
  
  	ds3232->client = client;
  	i2c_set_clientdata(client, ds3232);
  
  	INIT_WORK(&ds3232->work, ds3232_work);
  	mutex_init(&ds3232->mutex);
  
  	ret = ds3232_check_rtc_status(client);
  	if (ret)
  		return ret;
  
  	ds3232->rtc = devm_rtc_device_register(&client->dev, client->name,
  					  &ds3232_rtc_ops, THIS_MODULE);
  	if (IS_ERR(ds3232->rtc)) {
  		dev_err(&client->dev, "unable to register the class device
  ");
  		return PTR_ERR(ds3232->rtc);
  	}
  
  	if (client->irq >= 0) {
  		ret = devm_request_irq(&client->dev, client->irq, ds3232_irq, 0,
  				 "ds3232", client);
  		if (ret) {
  			dev_err(&client->dev, "unable to request IRQ
  ");
  			return ret;
  		}
  	}
  
  	return 0;
  }
  
  static int ds3232_remove(struct i2c_client *client)
  {
  	struct ds3232 *ds3232 = i2c_get_clientdata(client);
  
  	if (client->irq >= 0) {
  		mutex_lock(&ds3232->mutex);
  		ds3232->exiting = 1;
  		mutex_unlock(&ds3232->mutex);
  
  		devm_free_irq(&client->dev, client->irq, client);
  		cancel_work_sync(&ds3232->work);
  	}
  
  	return 0;
  }
  
  static const struct i2c_device_id ds3232_id[] = {
  	{ "ds3232", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, ds3232_id);
  
  static struct i2c_driver ds3232_driver = {
  	.driver = {
  		.name = "rtc-ds3232",
  		.owner = THIS_MODULE,
  	},
  	.probe = ds3232_probe,
  	.remove = ds3232_remove,
  	.id_table = ds3232_id,
  };
  
  module_i2c_driver(ds3232_driver);
  
  MODULE_AUTHOR("Srikanth Srinivasan <srikanth.srinivasan@freescale.com>");
  MODULE_DESCRIPTION("Maxim/Dallas DS3232 RTC Driver");
  MODULE_LICENSE("GPL");