/*
   * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
   *
   * Based on code by Randy Vinson <rvinson@mvista.com>,
   * which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.
   *
   * Copyright (C) 2006-2007 Freescale Semiconductor
   *
   * 2005 (c) MontaVista Software, Inc. This file is licensed under
   * the terms of the GNU General Public License version 2. This program
   * is licensed "as is" without any warranty of any kind, whether express
   * or implied.
   */
  /*
   * 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>

  #include <linux/pm.h>

  
  #define DS1374_REG_TOD0		0x00 /* Time of Day */
  #define DS1374_REG_TOD1		0x01
  #define DS1374_REG_TOD2		0x02
  #define DS1374_REG_TOD3		0x03
  #define DS1374_REG_WDALM0	0x04 /* Watchdog/Alarm */
  #define DS1374_REG_WDALM1	0x05
  #define DS1374_REG_WDALM2	0x06
  #define DS1374_REG_CR		0x07 /* Control */
  #define DS1374_REG_CR_AIE	0x01 /* Alarm Int. Enable */
  #define DS1374_REG_CR_WDALM	0x20 /* 1=Watchdog, 0=Alarm */
  #define DS1374_REG_CR_WACE	0x40 /* WD/Alarm counter enable */
  #define DS1374_REG_SR		0x08 /* Status */
  #define DS1374_REG_SR_OSF	0x80 /* Oscillator Stop Flag */
  #define DS1374_REG_SR_AF	0x01 /* Alarm Flag */
  #define DS1374_REG_TCR		0x09 /* Trickle Charge */

  static const struct i2c_device_id ds1374_id[] = {

  	{ "ds1374", 0 },

  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, ds1374_id);

  struct ds1374 {
  	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 ds1374_driver;
  
  static int ds1374_read_rtc(struct i2c_client *client, u32 *time,

  			   int reg, int nbytes)

  {
  	u8 buf[4];
  	int ret;
  	int i;
  
  	if (nbytes > 4) {
  		WARN_ON(1);
  		return -EINVAL;
  	}
  
  	ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
  
  	if (ret < 0)
  		return ret;
  	if (ret < nbytes)
  		return -EIO;
  
  	for (i = nbytes - 1, *time = 0; i >= 0; i--)
  		*time = (*time << 8) | buf[i];
  
  	return 0;
  }
  
  static int ds1374_write_rtc(struct i2c_client *client, u32 time,

  			    int reg, int nbytes)

  {
  	u8 buf[4];
  	int i;
  
  	if (nbytes > 4) {
  		WARN_ON(1);
  		return -EINVAL;
  	}
  
  	for (i = 0; i < nbytes; i++) {
  		buf[i] = time & 0xff;
  		time >>= 8;
  	}
  
  	return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
  }
  
  static int ds1374_check_rtc_status(struct i2c_client *client)
  {
  	int ret = 0;
  	int control, stat;
  
  	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
  	if (stat < 0)
  		return stat;
  
  	if (stat & DS1374_REG_SR_OSF)
  		dev_warn(&client->dev,

  			 "oscillator discontinuity flagged, time unreliable
  ");

  
  	stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
  
  	ret = i2c_smbus_write_byte_data(client, DS1374_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, DS1374_REG_CR);
  	if (control < 0)
  		return control;
  
  	control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
  	return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
  }
  
  static int ds1374_read_time(struct device *dev, struct rtc_time *time)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	u32 itime;
  	int ret;
  
  	ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
  	if (!ret)
  		rtc_time_to_tm(itime, time);
  
  	return ret;
  }
  
  static int ds1374_set_time(struct device *dev, struct rtc_time *time)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	unsigned long itime;
  
  	rtc_tm_to_time(time, &itime);
  	return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
  }
  
  /* The ds1374 has a decrementer for an alarm, rather than a comparator.
   * If the time of day is changed, then the alarm will need to be
   * reset.
   */
  static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ds1374 *ds1374 = i2c_get_clientdata(client);
  	u32 now, cur_alarm;
  	int cr, sr;
  	int ret = 0;

  	if (client->irq <= 0)

  		return -EINVAL;
  
  	mutex_lock(&ds1374->mutex);
  
  	cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
  	if (ret < 0)
  		goto out;
  
  	sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
  	if (ret < 0)
  		goto out;
  
  	ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
  	if (ret)
  		goto out;
  
  	ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
  	if (ret)
  		goto out;
  
  	rtc_time_to_tm(now + cur_alarm, &alarm->time);
  	alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
  	alarm->pending = !!(sr & DS1374_REG_SR_AF);
  
  out:
  	mutex_unlock(&ds1374->mutex);
  	return ret;
  }
  
  static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ds1374 *ds1374 = i2c_get_clientdata(client);
  	struct rtc_time now;
  	unsigned long new_alarm, itime;
  	int cr;
  	int ret = 0;

  	if (client->irq <= 0)

  		return -EINVAL;
  
  	ret = ds1374_read_time(dev, &now);
  	if (ret < 0)
  		return ret;
  
  	rtc_tm_to_time(&alarm->time, &new_alarm);
  	rtc_tm_to_time(&now, &itime);

  	/* This can happen due to races, in addition to dates that are
  	 * truly in the past.  To avoid requiring the caller to check for
  	 * races, dates in the past are assumed to be in the recent past
  	 * (i.e. not something that we'd rather the caller know about via
  	 * an error), and the alarm is set to go off as soon as possible.
  	 */

  	if (time_before_eq(new_alarm, itime))

  		new_alarm = 1;

  	else
  		new_alarm -= itime;

  
  	mutex_lock(&ds1374->mutex);
  
  	ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
  	if (ret < 0)
  		goto out;
  
  	/* Disable any existing alarm before setting the new one
  	 * (or lack thereof). */
  	cr &= ~DS1374_REG_CR_WACE;
  
  	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
  	if (ret < 0)
  		goto out;
  
  	ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
  	if (ret)
  		goto out;
  
  	if (alarm->enabled) {
  		cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
  		cr &= ~DS1374_REG_CR_WDALM;
  
  		ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
  	}
  
  out:
  	mutex_unlock(&ds1374->mutex);
  	return ret;
  }
  
  static irqreturn_t ds1374_irq(int irq, void *dev_id)
  {
  	struct i2c_client *client = dev_id;
  	struct ds1374 *ds1374 = i2c_get_clientdata(client);
  
  	disable_irq_nosync(irq);
  	schedule_work(&ds1374->work);
  	return IRQ_HANDLED;
  }
  
  static void ds1374_work(struct work_struct *work)
  {
  	struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
  	struct i2c_client *client = ds1374->client;
  	int stat, control;
  
  	mutex_lock(&ds1374->mutex);
  
  	stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
  	if (stat < 0)

  		goto unlock;

  
  	if (stat & DS1374_REG_SR_AF) {
  		stat &= ~DS1374_REG_SR_AF;
  		i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
  
  		control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
  		if (control < 0)
  			goto out;
  
  		control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
  		i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);

  		rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);

  	}
  
  out:
  	if (!ds1374->exiting)
  		enable_irq(client->irq);

  unlock:

  	mutex_unlock(&ds1374->mutex);
  }

  static int ds1374_alarm_irq_enable(struct device *dev, unsigned int enabled)

  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ds1374 *ds1374 = i2c_get_clientdata(client);

  	int ret;

  
  	mutex_lock(&ds1374->mutex);

  	ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
  	if (ret < 0)
  		goto out;

  	if (enabled) {

  		ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
  		ret &= ~DS1374_REG_CR_WDALM;

  	} else {
  		ret &= ~DS1374_REG_CR_WACE;

  	}

  	ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);

  
  out:
  	mutex_unlock(&ds1374->mutex);
  	return ret;
  }
  
  static const struct rtc_class_ops ds1374_rtc_ops = {
  	.read_time = ds1374_read_time,
  	.set_time = ds1374_set_time,
  	.read_alarm = ds1374_read_alarm,
  	.set_alarm = ds1374_set_alarm,

  	.alarm_irq_enable = ds1374_alarm_irq_enable,

  };

  static int ds1374_probe(struct i2c_client *client,
  			const struct i2c_device_id *id)

  {
  	struct ds1374 *ds1374;
  	int ret;

  	ds1374 = devm_kzalloc(&client->dev, sizeof(struct ds1374), GFP_KERNEL);

  	if (!ds1374)
  		return -ENOMEM;
  
  	ds1374->client = client;
  	i2c_set_clientdata(client, ds1374);
  
  	INIT_WORK(&ds1374->work, ds1374_work);
  	mutex_init(&ds1374->mutex);
  
  	ret = ds1374_check_rtc_status(client);
  	if (ret)

  		return ret;

  	if (client->irq > 0) {

  		ret = devm_request_irq(&client->dev, client->irq, ds1374_irq, 0,

  					"ds1374", client);

  		if (ret) {
  			dev_err(&client->dev, "unable to request IRQ
  ");

  			return ret;

  		}

  
  		device_set_wakeup_capable(&client->dev, 1);

  	}

  	ds1374->rtc = devm_rtc_device_register(&client->dev, client->name,

  						&ds1374_rtc_ops, THIS_MODULE);

  	if (IS_ERR(ds1374->rtc)) {

  		dev_err(&client->dev, "unable to register the class device
  ");

  		return PTR_ERR(ds1374->rtc);

  	}
  
  	return 0;

  }

  static int ds1374_remove(struct i2c_client *client)

  {
  	struct ds1374 *ds1374 = i2c_get_clientdata(client);

  	if (client->irq > 0) {

  		mutex_lock(&ds1374->mutex);
  		ds1374->exiting = 1;
  		mutex_unlock(&ds1374->mutex);

  		devm_free_irq(&client->dev, client->irq, client);

  		cancel_work_sync(&ds1374->work);

  	}

  	return 0;
  }

  #ifdef CONFIG_PM_SLEEP

  static int ds1374_suspend(struct device *dev)

  {

  	struct i2c_client *client = to_i2c_client(dev);

  	if (client->irq >= 0 && device_may_wakeup(&client->dev))
  		enable_irq_wake(client->irq);
  	return 0;
  }

  static int ds1374_resume(struct device *dev)

  {

  	struct i2c_client *client = to_i2c_client(dev);

  	if (client->irq >= 0 && device_may_wakeup(&client->dev))
  		disable_irq_wake(client->irq);
  	return 0;
  }

  #endif

  
  static SIMPLE_DEV_PM_OPS(ds1374_pm, ds1374_suspend, ds1374_resume);

  static struct i2c_driver ds1374_driver = {
  	.driver = {
  		.name = "rtc-ds1374",
  		.owner = THIS_MODULE,

  		.pm = &ds1374_pm,

  	},
  	.probe = ds1374_probe,

  	.remove = ds1374_remove,

  	.id_table = ds1374_id,

  };

  module_i2c_driver(ds1374_driver);

  
  MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
  MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
  MODULE_LICENSE("GPL");