/*
   * Copyright (C) ST-Ericsson SA 2010
   *
   * License terms: GNU General Public License (GPL) version 2
   * Author: Virupax Sadashivpetimath <virupax.sadashivpetimath@stericsson.com>
   *
   * RTC clock driver for the RTC part of the AB8500 Power management chip.
   * Based on RTC clock driver for the AB3100 Analog Baseband Chip by
   * Linus Walleij <linus.walleij@stericsson.com>
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/platform_device.h>
  #include <linux/rtc.h>

  #include <linux/mfd/abx500.h>

  #include <linux/mfd/abx500/ab8500.h>

  #include <linux/delay.h>

  #define AB8500_RTC_SOFF_STAT_REG	0x00
  #define AB8500_RTC_CC_CONF_REG		0x01
  #define AB8500_RTC_READ_REQ_REG		0x02
  #define AB8500_RTC_WATCH_TSECMID_REG	0x03
  #define AB8500_RTC_WATCH_TSECHI_REG	0x04
  #define AB8500_RTC_WATCH_TMIN_LOW_REG	0x05
  #define AB8500_RTC_WATCH_TMIN_MID_REG	0x06
  #define AB8500_RTC_WATCH_TMIN_HI_REG	0x07
  #define AB8500_RTC_ALRM_MIN_LOW_REG	0x08
  #define AB8500_RTC_ALRM_MIN_MID_REG	0x09
  #define AB8500_RTC_ALRM_MIN_HI_REG	0x0A
  #define AB8500_RTC_STAT_REG		0x0B
  #define AB8500_RTC_BKUP_CHG_REG		0x0C
  #define AB8500_RTC_FORCE_BKUP_REG	0x0D
  #define AB8500_RTC_CALIB_REG		0x0E
  #define AB8500_RTC_SWITCH_STAT_REG	0x0F

  
  /* RtcReadRequest bits */
  #define RTC_READ_REQUEST		0x01
  #define RTC_WRITE_REQUEST		0x02
  
  /* RtcCtrl bits */
  #define RTC_ALARM_ENA			0x04
  #define RTC_STATUS_DATA			0x01
  
  #define COUNTS_PER_SEC			(0xF000 / 60)
  #define AB8500_RTC_EPOCH		2000

  static const u8 ab8500_rtc_time_regs[] = {

  	AB8500_RTC_WATCH_TMIN_HI_REG, AB8500_RTC_WATCH_TMIN_MID_REG,
  	AB8500_RTC_WATCH_TMIN_LOW_REG, AB8500_RTC_WATCH_TSECHI_REG,
  	AB8500_RTC_WATCH_TSECMID_REG
  };

  static const u8 ab8500_rtc_alarm_regs[] = {

  	AB8500_RTC_ALRM_MIN_HI_REG, AB8500_RTC_ALRM_MIN_MID_REG,
  	AB8500_RTC_ALRM_MIN_LOW_REG
  };
  
  /* Calculate the seconds from 1970 to 01-01-2000 00:00:00 */
  static unsigned long get_elapsed_seconds(int year)
  {
  	unsigned long secs;
  	struct rtc_time tm = {
  		.tm_year = year - 1900,
  		.tm_mday = 1,
  	};
  
  	/*
  	 * This function calculates secs from 1970 and not from
  	 * 1900, even if we supply the offset from year 1900.
  	 */
  	rtc_tm_to_time(&tm, &secs);
  	return secs;
  }
  
  static int ab8500_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {

  	unsigned long timeout = jiffies + HZ;
  	int retval, i;
  	unsigned long mins, secs;
  	unsigned char buf[ARRAY_SIZE(ab8500_rtc_time_regs)];

  	u8 value;

  
  	/* Request a data read */

  	retval = abx500_set_register_interruptible(dev,
  		AB8500_RTC, AB8500_RTC_READ_REQ_REG, RTC_READ_REQUEST);

  	if (retval < 0)
  		return retval;
  
  	/* Early AB8500 chips will not clear the rtc read request bit */

  	if (abx500_get_chip_id(dev) == 0) {

  		usleep_range(1000, 1000);

  	} else {
  		/* Wait for some cycles after enabling the rtc read in ab8500 */
  		while (time_before(jiffies, timeout)) {

  			retval = abx500_get_register_interruptible(dev,
  				AB8500_RTC, AB8500_RTC_READ_REQ_REG, &value);

  			if (retval < 0)
  				return retval;

  			if (!(value & RTC_READ_REQUEST))

  				break;

  			usleep_range(1000, 5000);

  		}
  	}
  
  	/* Read the Watchtime registers */
  	for (i = 0; i < ARRAY_SIZE(ab8500_rtc_time_regs); i++) {

  		retval = abx500_get_register_interruptible(dev,
  			AB8500_RTC, ab8500_rtc_time_regs[i], &value);

  		if (retval < 0)
  			return retval;

  		buf[i] = value;

  	}
  
  	mins = (buf[0] << 16) | (buf[1] << 8) | buf[2];
  
  	secs =	(buf[3] << 8) | buf[4];
  	secs =	secs / COUNTS_PER_SEC;
  	secs =	secs + (mins * 60);
  
  	/* Add back the initially subtracted number of seconds */
  	secs += get_elapsed_seconds(AB8500_RTC_EPOCH);
  
  	rtc_time_to_tm(secs, tm);
  	return rtc_valid_tm(tm);
  }
  
  static int ab8500_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {

  	int retval, i;
  	unsigned char buf[ARRAY_SIZE(ab8500_rtc_time_regs)];
  	unsigned long no_secs, no_mins, secs = 0;
  
  	if (tm->tm_year < (AB8500_RTC_EPOCH - 1900)) {
  		dev_dbg(dev, "year should be equal to or greater than %d
  ",
  				AB8500_RTC_EPOCH);
  		return -EINVAL;
  	}
  
  	/* Get the number of seconds since 1970 */
  	rtc_tm_to_time(tm, &secs);
  
  	/*
  	 * Convert it to the number of seconds since 01-01-2000 00:00:00, since
  	 * we only have a small counter in the RTC.
  	 */
  	secs -= get_elapsed_seconds(AB8500_RTC_EPOCH);
  
  	no_mins = secs / 60;
  
  	no_secs = secs % 60;
  	/* Make the seconds count as per the RTC resolution */
  	no_secs = no_secs * COUNTS_PER_SEC;
  
  	buf[4] = no_secs & 0xFF;
  	buf[3] = (no_secs >> 8) & 0xFF;
  
  	buf[2] = no_mins & 0xFF;
  	buf[1] = (no_mins >> 8) & 0xFF;
  	buf[0] = (no_mins >> 16) & 0xFF;
  
  	for (i = 0; i < ARRAY_SIZE(ab8500_rtc_time_regs); i++) {

  		retval = abx500_set_register_interruptible(dev, AB8500_RTC,
  			ab8500_rtc_time_regs[i], buf[i]);

  		if (retval < 0)
  			return retval;
  	}
  
  	/* Request a data write */

  	return abx500_set_register_interruptible(dev, AB8500_RTC,
  		AB8500_RTC_READ_REQ_REG, RTC_WRITE_REQUEST);

  }
  
  static int ab8500_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {

  	int retval, i;

  	u8 rtc_ctrl, value;

  	unsigned char buf[ARRAY_SIZE(ab8500_rtc_alarm_regs)];
  	unsigned long secs, mins;
  
  	/* Check if the alarm is enabled or not */

  	retval = abx500_get_register_interruptible(dev, AB8500_RTC,
  		AB8500_RTC_STAT_REG, &rtc_ctrl);
  	if (retval < 0)
  		return retval;

  
  	if (rtc_ctrl & RTC_ALARM_ENA)
  		alarm->enabled = 1;
  	else
  		alarm->enabled = 0;
  
  	alarm->pending = 0;
  
  	for (i = 0; i < ARRAY_SIZE(ab8500_rtc_alarm_regs); i++) {

  		retval = abx500_get_register_interruptible(dev, AB8500_RTC,
  			ab8500_rtc_alarm_regs[i], &value);

  		if (retval < 0)
  			return retval;

  		buf[i] = value;

  	}
  
  	mins = (buf[0] << 16) | (buf[1] << 8) | (buf[2]);
  	secs = mins * 60;
  
  	/* Add back the initially subtracted number of seconds */
  	secs += get_elapsed_seconds(AB8500_RTC_EPOCH);
  
  	rtc_time_to_tm(secs, &alarm->time);
  
  	return rtc_valid_tm(&alarm->time);
  }
  
  static int ab8500_rtc_irq_enable(struct device *dev, unsigned int enabled)
  {

  	return abx500_mask_and_set_register_interruptible(dev, AB8500_RTC,
  		AB8500_RTC_STAT_REG, RTC_ALARM_ENA,
  		enabled ? RTC_ALARM_ENA : 0);

  }
  
  static int ab8500_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {

  	int retval, i;
  	unsigned char buf[ARRAY_SIZE(ab8500_rtc_alarm_regs)];
  	unsigned long mins, secs = 0;
  
  	if (alarm->time.tm_year < (AB8500_RTC_EPOCH - 1900)) {
  		dev_dbg(dev, "year should be equal to or greater than %d
  ",
  				AB8500_RTC_EPOCH);
  		return -EINVAL;
  	}
  
  	/* Get the number of seconds since 1970 */
  	rtc_tm_to_time(&alarm->time, &secs);
  
  	/*
  	 * Convert it to the number of seconds since 01-01-2000 00:00:00, since
  	 * we only have a small counter in the RTC.
  	 */
  	secs -= get_elapsed_seconds(AB8500_RTC_EPOCH);
  
  	mins = secs / 60;
  
  	buf[2] = mins & 0xFF;
  	buf[1] = (mins >> 8) & 0xFF;
  	buf[0] = (mins >> 16) & 0xFF;
  
  	/* Set the alarm time */
  	for (i = 0; i < ARRAY_SIZE(ab8500_rtc_alarm_regs); i++) {

  		retval = abx500_set_register_interruptible(dev, AB8500_RTC,
  			ab8500_rtc_alarm_regs[i], buf[i]);

  		if (retval < 0)
  			return retval;
  	}
  
  	return ab8500_rtc_irq_enable(dev, alarm->enabled);
  }

  
  static int ab8500_rtc_set_calibration(struct device *dev, int calibration)
  {
  	int retval;
  	u8  rtccal = 0;
  
  	/*
  	 * Check that the calibration value (which is in units of 0.5
  	 * parts-per-million) is in the AB8500's range for RtcCalibration
  	 * register. -128 (0x80) is not permitted because the AB8500 uses
  	 * a sign-bit rather than two's complement, so 0x80 is just another
  	 * representation of zero.
  	 */
  	if ((calibration < -127) || (calibration > 127)) {
  		dev_err(dev, "RtcCalibration value outside permitted range
  ");
  		return -EINVAL;
  	}
  
  	/*
  	 * The AB8500 uses sign (in bit7) and magnitude (in bits0-7)
  	 * so need to convert to this sort of representation before writing
  	 * into RtcCalibration register...
  	 */
  	if (calibration >= 0)
  		rtccal = 0x7F & calibration;
  	else
  		rtccal = ~(calibration - 1) | 0x80;
  
  	retval = abx500_set_register_interruptible(dev, AB8500_RTC,
  			AB8500_RTC_CALIB_REG, rtccal);
  
  	return retval;
  }
  
  static int ab8500_rtc_get_calibration(struct device *dev, int *calibration)
  {
  	int retval;
  	u8  rtccal = 0;
  
  	retval =  abx500_get_register_interruptible(dev, AB8500_RTC,
  			AB8500_RTC_CALIB_REG, &rtccal);
  	if (retval >= 0) {
  		/*
  		 * The AB8500 uses sign (in bit7) and magnitude (in bits0-7)
  		 * so need to convert value from RtcCalibration register into
  		 * a two's complement signed value...
  		 */
  		if (rtccal & 0x80)
  			*calibration = 0 - (rtccal & 0x7F);
  		else
  			*calibration = 0x7F & rtccal;
  	}
  
  	return retval;
  }
  
  static ssize_t ab8500_sysfs_store_rtc_calibration(struct device *dev,
  				struct device_attribute *attr,
  				const char *buf, size_t count)
  {
  	int retval;
  	int calibration = 0;
  
  	if (sscanf(buf, " %i ", &calibration) != 1) {
  		dev_err(dev, "Failed to store RTC calibration attribute
  ");
  		return -EINVAL;
  	}
  
  	retval = ab8500_rtc_set_calibration(dev, calibration);
  
  	return retval ? retval : count;
  }
  
  static ssize_t ab8500_sysfs_show_rtc_calibration(struct device *dev,
  				struct device_attribute *attr, char *buf)
  {
  	int  retval = 0;
  	int  calibration = 0;
  
  	retval = ab8500_rtc_get_calibration(dev, &calibration);
  	if (retval < 0) {
  		dev_err(dev, "Failed to read RTC calibration attribute
  ");
  		sprintf(buf, "0
  ");
  		return retval;
  	}
  
  	return sprintf(buf, "%d
  ", calibration);
  }
  
  static DEVICE_ATTR(rtc_calibration, S_IRUGO | S_IWUSR,
  		   ab8500_sysfs_show_rtc_calibration,
  		   ab8500_sysfs_store_rtc_calibration);
  
  static int ab8500_sysfs_rtc_register(struct device *dev)
  {
  	return device_create_file(dev, &dev_attr_rtc_calibration);
  }
  
  static void ab8500_sysfs_rtc_unregister(struct device *dev)
  {
  	device_remove_file(dev, &dev_attr_rtc_calibration);
  }

  static irqreturn_t rtc_alarm_handler(int irq, void *data)
  {
  	struct rtc_device *rtc = data;
  	unsigned long events = RTC_IRQF | RTC_AF;
  
  	dev_dbg(&rtc->dev, "%s
  ", __func__);
  	rtc_update_irq(rtc, 1, events);
  
  	return IRQ_HANDLED;
  }
  
  static const struct rtc_class_ops ab8500_rtc_ops = {
  	.read_time		= ab8500_rtc_read_time,
  	.set_time		= ab8500_rtc_set_time,
  	.read_alarm		= ab8500_rtc_read_alarm,
  	.set_alarm		= ab8500_rtc_set_alarm,
  	.alarm_irq_enable	= ab8500_rtc_irq_enable,
  };
  
  static int __devinit ab8500_rtc_probe(struct platform_device *pdev)
  {

  	int err;
  	struct rtc_device *rtc;

  	u8 rtc_ctrl;

  	int irq;
  
  	irq = platform_get_irq_byname(pdev, "ALARM");
  	if (irq < 0)
  		return irq;
  
  	/* For RTC supply test */

  	err = abx500_mask_and_set_register_interruptible(&pdev->dev, AB8500_RTC,
  		AB8500_RTC_STAT_REG, RTC_STATUS_DATA, RTC_STATUS_DATA);

  	if (err < 0)
  		return err;
  
  	/* Wait for reset by the PorRtc */

  	usleep_range(1000, 5000);

  	err = abx500_get_register_interruptible(&pdev->dev, AB8500_RTC,
  		AB8500_RTC_STAT_REG, &rtc_ctrl);
  	if (err < 0)
  		return err;

  
  	/* Check if the RTC Supply fails */
  	if (!(rtc_ctrl & RTC_STATUS_DATA)) {
  		dev_err(&pdev->dev, "RTC supply failure
  ");
  		return -ENODEV;
  	}

  	device_init_wakeup(&pdev->dev, true);

  	rtc = rtc_device_register("ab8500-rtc", &pdev->dev, &ab8500_rtc_ops,
  			THIS_MODULE);
  	if (IS_ERR(rtc)) {
  		dev_err(&pdev->dev, "Registration failed
  ");
  		err = PTR_ERR(rtc);
  		return err;
  	}

  	err = request_threaded_irq(irq, NULL, rtc_alarm_handler,
  		IRQF_NO_SUSPEND, "ab8500-rtc", rtc);

  	if (err < 0) {
  		rtc_device_unregister(rtc);
  		return err;
  	}
  
  	platform_set_drvdata(pdev, rtc);

  
  	err = ab8500_sysfs_rtc_register(&pdev->dev);
  	if (err) {
  		dev_err(&pdev->dev, "sysfs RTC failed to register
  ");
  		return err;
  	}

  	return 0;
  }
  
  static int __devexit ab8500_rtc_remove(struct platform_device *pdev)
  {
  	struct rtc_device *rtc = platform_get_drvdata(pdev);
  	int irq = platform_get_irq_byname(pdev, "ALARM");

  	ab8500_sysfs_rtc_unregister(&pdev->dev);

  	free_irq(irq, rtc);
  	rtc_device_unregister(rtc);
  	platform_set_drvdata(pdev, NULL);
  
  	return 0;
  }
  
  static struct platform_driver ab8500_rtc_driver = {
  	.driver = {
  		.name = "ab8500-rtc",
  		.owner = THIS_MODULE,
  	},
  	.probe	= ab8500_rtc_probe,
  	.remove = __devexit_p(ab8500_rtc_remove),
  };

  module_platform_driver(ab8500_rtc_driver);

  MODULE_AUTHOR("Virupax Sadashivpetimath <virupax.sadashivpetimath@stericsson.com>");
  MODULE_DESCRIPTION("AB8500 RTC Driver");
  MODULE_LICENSE("GPL v2");