/*
   * Copyright (C) 2007-2009 ST-Ericsson AB
   * License terms: GNU General Public License (GPL) version 2
   * RTC clock driver for the AB3100 Analog Baseband Chip
   * Author: 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>

  
  /* Clock rate in Hz */
  #define AB3100_RTC_CLOCK_RATE	32768
  
  /*
   * The AB3100 RTC registers. These are the same for
   * AB3000 and AB3100.
   * Control register:
   * Bit 0: RTC Monitor cleared=0, active=1, if you set it
   *        to 1 it remains active until RTC power is lost.
   * Bit 1: 32 kHz Oscillator, 0 = on, 1 = bypass
   * Bit 2: Alarm on, 0 = off, 1 = on
   * Bit 3: 32 kHz buffer disabling, 0 = enabled, 1 = disabled
   */
  #define AB3100_RTC		0x53
  /* default setting, buffer disabled, alarm on */
  #define RTC_SETTING		0x30
  /* Alarm when AL0-AL3 == TI0-TI3  */
  #define AB3100_AL0		0x56
  #define AB3100_AL1		0x57
  #define AB3100_AL2		0x58
  #define AB3100_AL3		0x59
  /* This 48-bit register that counts up at 32768 Hz */
  #define AB3100_TI0		0x5a
  #define AB3100_TI1		0x5b
  #define AB3100_TI2		0x5c
  #define AB3100_TI3		0x5d
  #define AB3100_TI4		0x5e
  #define AB3100_TI5		0x5f
  
  /*
   * RTC clock functions and device struct declaration
   */

  static int ab3100_rtc_set_mmss(struct device *dev, time64_t secs)

  {

  	u8 regs[] = {AB3100_TI0, AB3100_TI1, AB3100_TI2,
  		     AB3100_TI3, AB3100_TI4, AB3100_TI5};
  	unsigned char buf[6];

  	u64 hw_counter = secs * AB3100_RTC_CLOCK_RATE * 2;

  	int err = 0;
  	int i;

  	buf[0] = (hw_counter) & 0xFF;
  	buf[1] = (hw_counter >> 8) & 0xFF;
  	buf[2] = (hw_counter >> 16) & 0xFF;
  	buf[3] = (hw_counter >> 24) & 0xFF;
  	buf[4] = (hw_counter >> 32) & 0xFF;
  	buf[5] = (hw_counter >> 40) & 0xFF;

  
  	for (i = 0; i < 6; i++) {

  		err = abx500_set_register_interruptible(dev, 0,

  							regs[i], buf[i]);
  		if (err)
  			return err;
  	}
  
  	/* Set the flag to mark that the clock is now set */

  	return abx500_mask_and_set_register_interruptible(dev, 0,

  							  AB3100_RTC,

  							  0x01, 0x01);

  
  }
  
  static int ab3100_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {

  	time64_t time;

  	u8 rtcval;
  	int err;

  	err = abx500_get_register_interruptible(dev, 0,

  						AB3100_RTC, &rtcval);
  	if (err)
  		return err;
  
  	if (!(rtcval & 0x01)) {
  		dev_info(dev, "clock not set (lost power)");
  		return -EINVAL;
  	} else {

  		u64 hw_counter;

  		u8 buf[6];
  
  		/* Read out time registers */

  		err = abx500_get_register_page_interruptible(dev, 0,

  							     AB3100_TI0,
  							     buf, 6);
  		if (err != 0)
  			return err;

  		hw_counter = ((u64) buf[5] << 40) | ((u64) buf[4] << 32) |

  			((u64) buf[3] << 24) | ((u64) buf[2] << 16) |
  			((u64) buf[1] << 8) | (u64) buf[0];

  		time = hw_counter / (u64) (AB3100_RTC_CLOCK_RATE * 2);

  	}

  	rtc_time64_to_tm(time, tm);

  
  	return rtc_valid_tm(tm);
  }
  
  static int ab3100_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {

  	time64_t time;
  	u64 hw_counter;

  	u8 buf[6];
  	u8 rtcval;
  	int err;
  
  	/* Figure out if alarm is enabled or not */

  	err = abx500_get_register_interruptible(dev, 0,

  						AB3100_RTC, &rtcval);
  	if (err)
  		return err;
  	if (rtcval & 0x04)
  		alarm->enabled = 1;
  	else
  		alarm->enabled = 0;
  	/* No idea how this could be represented */
  	alarm->pending = 0;
  	/* Read out alarm registers, only 4 bytes */

  	err = abx500_get_register_page_interruptible(dev, 0,

  						     AB3100_AL0, buf, 4);
  	if (err)
  		return err;

  	hw_counter = ((u64) buf[3] << 40) | ((u64) buf[2] << 32) |

  		((u64) buf[1] << 24) | ((u64) buf[0] << 16);

  	time = hw_counter / (u64) (AB3100_RTC_CLOCK_RATE * 2);

  	rtc_time64_to_tm(time, &alarm->time);

  
  	return rtc_valid_tm(&alarm->time);
  }
  
  static int ab3100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
  {

  	u8 regs[] = {AB3100_AL0, AB3100_AL1, AB3100_AL2, AB3100_AL3};
  	unsigned char buf[4];

  	time64_t secs;
  	u64 hw_counter;

  	int err;
  	int i;

  	secs = rtc_tm_to_time64(&alarm->time);
  	hw_counter = secs * AB3100_RTC_CLOCK_RATE * 2;
  	buf[0] = (hw_counter >> 16) & 0xFF;
  	buf[1] = (hw_counter >> 24) & 0xFF;
  	buf[2] = (hw_counter >> 32) & 0xFF;
  	buf[3] = (hw_counter >> 40) & 0xFF;

  
  	/* Set the alarm */
  	for (i = 0; i < 4; i++) {

  		err = abx500_set_register_interruptible(dev, 0,

  							regs[i], buf[i]);
  		if (err)
  			return err;
  	}
  	/* Then enable the alarm */

  	return abx500_mask_and_set_register_interruptible(dev, 0,
  							  AB3100_RTC, (1 << 2),

  							  alarm->enabled << 2);
  }
  
  static int ab3100_rtc_irq_enable(struct device *dev, unsigned int enabled)
  {

  	/*
  	 * It's not possible to enable/disable the alarm IRQ for this RTC.
  	 * It does not actually trigger any IRQ: instead its only function is
  	 * to power up the system, if it wasn't on. This will manifest as
  	 * a "power up cause" in the AB3100 power driver (battery charging etc)
  	 * and need to be handled there instead.
  	 */
  	if (enabled)

  		return abx500_mask_and_set_register_interruptible(dev, 0,
  						    AB3100_RTC, (1 << 2),

  						    1 << 2);
  	else

  		return abx500_mask_and_set_register_interruptible(dev, 0,
  						    AB3100_RTC, (1 << 2),

  						    0);
  }
  
  static const struct rtc_class_ops ab3100_rtc_ops = {
  	.read_time	= ab3100_rtc_read_time,

  	.set_mmss64	= ab3100_rtc_set_mmss,

  	.read_alarm	= ab3100_rtc_read_alarm,
  	.set_alarm	= ab3100_rtc_set_alarm,
  	.alarm_irq_enable = ab3100_rtc_irq_enable,
  };
  
  static int __init ab3100_rtc_probe(struct platform_device *pdev)
  {
  	int err;
  	u8 regval;
  	struct rtc_device *rtc;

  
  	/* The first RTC register needs special treatment */

  	err = abx500_get_register_interruptible(&pdev->dev, 0,

  						AB3100_RTC, &regval);
  	if (err) {
  		dev_err(&pdev->dev, "unable to read RTC register
  ");
  		return -ENODEV;
  	}
  
  	if ((regval & 0xFE) != RTC_SETTING) {
  		dev_warn(&pdev->dev, "not default value in RTC reg 0x%x
  ",
  			 regval);
  	}
  
  	if ((regval & 1) == 0) {
  		/*
  		 * Set bit to detect power loss.
  		 * This bit remains until RTC power is lost.
  		 */
  		regval = 1 | RTC_SETTING;

  		err = abx500_set_register_interruptible(&pdev->dev, 0,

  							AB3100_RTC, regval);
  		/* Ignore any error on this write */
  	}

  	rtc = devm_rtc_device_register(&pdev->dev, "ab3100-rtc",
  					&ab3100_rtc_ops, THIS_MODULE);

  	if (IS_ERR(rtc)) {
  		err = PTR_ERR(rtc);
  		return err;
  	}

  	platform_set_drvdata(pdev, rtc);

  
  	return 0;
  }

  static struct platform_driver ab3100_rtc_driver = {
  	.driver = {
  		.name = "ab3100-rtc",

  	},

  };

  module_platform_driver_probe(ab3100_rtc_driver, ab3100_rtc_probe);

  
  MODULE_AUTHOR("Linus Walleij <linus.walleij@stericsson.com>");
  MODULE_DESCRIPTION("AB3100 RTC Driver");
  MODULE_LICENSE("GPL");