// SPDX-License-Identifier: GPL-2.0-only

  /*
   * An rtc driver for the Dallas/Maxim DS1685/DS1687 and related real-time
   * chips.
   *
   * Copyright (C) 2011-2014 Joshua Kinard <kumba@gentoo.org>.
   * Copyright (C) 2009 Matthias Fuchs <matthias.fuchs@esd-electronics.com>.
   *
   * References:
   *    DS1685/DS1687 3V/5V Real-Time Clocks, 19-5215, Rev 4/10.
   *    DS17x85/DS17x87 3V/5V Real-Time Clocks, 19-5222, Rev 4/10.
   *    DS1689/DS1693 3V/5V Serialized Real-Time Clocks, Rev 112105.
   *    Application Note 90, Using the Multiplex Bus RTC Extended Features.

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/bcd.h>
  #include <linux/delay.h>
  #include <linux/io.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/rtc.h>
  #include <linux/workqueue.h>
  
  #include <linux/rtc/ds1685.h>
  
  #ifdef CONFIG_PROC_FS
  #include <linux/proc_fs.h>
  #endif

  
  /* ----------------------------------------------------------------------- */

  /*
   *  Standard read/write
   *  all registers are mapped in CPU address space
   */

  
  /**
   * ds1685_read - read a value from an rtc register.
   * @rtc: pointer to the ds1685 rtc structure.
   * @reg: the register address to read.
   */
  static u8
  ds1685_read(struct ds1685_priv *rtc, int reg)
  {
  	return readb((u8 __iomem *)rtc->regs +
  		     (reg * rtc->regstep));
  }
  
  /**
   * ds1685_write - write a value to an rtc register.
   * @rtc: pointer to the ds1685 rtc structure.
   * @reg: the register address to write.
   * @value: value to write to the register.
   */
  static void
  ds1685_write(struct ds1685_priv *rtc, int reg, u8 value)
  {
  	writeb(value, ((u8 __iomem *)rtc->regs +
  		       (reg * rtc->regstep)));
  }
  /* ----------------------------------------------------------------------- */

  /*
   * Indirect read/write functions
   * access happens via address and data register mapped in CPU address space
   */
  
  /**
   * ds1685_indirect_read - read a value from an rtc register.
   * @rtc: pointer to the ds1685 rtc structure.
   * @reg: the register address to read.
   */
  static u8
  ds1685_indirect_read(struct ds1685_priv *rtc, int reg)
  {
  	writeb(reg, rtc->regs);
  	return readb(rtc->data);
  }
  
  /**
   * ds1685_indirect_write - write a value to an rtc register.
   * @rtc: pointer to the ds1685 rtc structure.
   * @reg: the register address to write.
   * @value: value to write to the register.
   */
  static void
  ds1685_indirect_write(struct ds1685_priv *rtc, int reg, u8 value)
  {
  	writeb(reg, rtc->regs);
  	writeb(value, rtc->data);
  }

  
  /* ----------------------------------------------------------------------- */
  /* Inlined functions */
  
  /**
   * ds1685_rtc_bcd2bin - bcd2bin wrapper in case platform doesn't support BCD.
   * @rtc: pointer to the ds1685 rtc structure.
   * @val: u8 time value to consider converting.
   * @bcd_mask: u8 mask value if BCD mode is used.
   * @bin_mask: u8 mask value if BIN mode is used.
   *
   * Returns the value, converted to BIN if originally in BCD and bcd_mode TRUE.
   */
  static inline u8
  ds1685_rtc_bcd2bin(struct ds1685_priv *rtc, u8 val, u8 bcd_mask, u8 bin_mask)
  {
  	if (rtc->bcd_mode)
  		return (bcd2bin(val) & bcd_mask);
  
  	return (val & bin_mask);
  }
  
  /**
   * ds1685_rtc_bin2bcd - bin2bcd wrapper in case platform doesn't support BCD.
   * @rtc: pointer to the ds1685 rtc structure.
   * @val: u8 time value to consider converting.
   * @bin_mask: u8 mask value if BIN mode is used.
   * @bcd_mask: u8 mask value if BCD mode is used.
   *
   * Returns the value, converted to BCD if originally in BIN and bcd_mode TRUE.
   */
  static inline u8
  ds1685_rtc_bin2bcd(struct ds1685_priv *rtc, u8 val, u8 bin_mask, u8 bcd_mask)
  {
  	if (rtc->bcd_mode)
  		return (bin2bcd(val) & bcd_mask);
  
  	return (val & bin_mask);
  }
  
  /**

   * s1685_rtc_check_mday - check validity of the day of month.
   * @rtc: pointer to the ds1685 rtc structure.
   * @mday: day of month.
   *
   * Returns -EDOM if the day of month is not within 1..31 range.
   */
  static inline int
  ds1685_rtc_check_mday(struct ds1685_priv *rtc, u8 mday)
  {
  	if (rtc->bcd_mode) {
  		if (mday < 0x01 || mday > 0x31 || (mday & 0x0f) > 0x09)
  			return -EDOM;
  	} else {
  		if (mday < 1 || mday > 31)
  			return -EDOM;
  	}
  	return 0;
  }
  
  /**

   * ds1685_rtc_switch_to_bank0 - switch the rtc to bank 0.
   * @rtc: pointer to the ds1685 rtc structure.
   */
  static inline void
  ds1685_rtc_switch_to_bank0(struct ds1685_priv *rtc)
  {
  	rtc->write(rtc, RTC_CTRL_A,
  		   (rtc->read(rtc, RTC_CTRL_A) & ~(RTC_CTRL_A_DV0)));
  }
  
  /**
   * ds1685_rtc_switch_to_bank1 - switch the rtc to bank 1.
   * @rtc: pointer to the ds1685 rtc structure.
   */
  static inline void
  ds1685_rtc_switch_to_bank1(struct ds1685_priv *rtc)
  {
  	rtc->write(rtc, RTC_CTRL_A,
  		   (rtc->read(rtc, RTC_CTRL_A) | RTC_CTRL_A_DV0));
  }
  
  /**
   * ds1685_rtc_begin_data_access - prepare the rtc for data access.
   * @rtc: pointer to the ds1685 rtc structure.
   *
   * This takes several steps to prepare the rtc for access to get/set time
   * and alarm values from the rtc registers:
   *  - Sets the SET bit in Control Register B.
   *  - Reads Ext Control Register 4A and checks the INCR bit.
   *  - If INCR is active, a short delay is added before Ext Control Register 4A
   *    is read again in a loop until INCR is inactive.
   *  - Switches the rtc to bank 1.  This allows access to all relevant
   *    data for normal rtc operation, as bank 0 contains only the nvram.
   */
  static inline void
  ds1685_rtc_begin_data_access(struct ds1685_priv *rtc)
  {
  	/* Set the SET bit in Ctrl B */
  	rtc->write(rtc, RTC_CTRL_B,
  		   (rtc->read(rtc, RTC_CTRL_B) | RTC_CTRL_B_SET));
  
  	/* Read Ext Ctrl 4A and check the INCR bit to avoid a lockout. */
  	while (rtc->read(rtc, RTC_EXT_CTRL_4A) & RTC_CTRL_4A_INCR)
  		cpu_relax();
  
  	/* Switch to Bank 1 */
  	ds1685_rtc_switch_to_bank1(rtc);
  }
  
  /**
   * ds1685_rtc_end_data_access - end data access on the rtc.
   * @rtc: pointer to the ds1685 rtc structure.
   *
   * This ends what was started by ds1685_rtc_begin_data_access:
   *  - Switches the rtc back to bank 0.
   *  - Clears the SET bit in Control Register B.
   */
  static inline void
  ds1685_rtc_end_data_access(struct ds1685_priv *rtc)
  {
  	/* Switch back to Bank 0 */
  	ds1685_rtc_switch_to_bank1(rtc);
  
  	/* Clear the SET bit in Ctrl B */
  	rtc->write(rtc, RTC_CTRL_B,
  		   (rtc->read(rtc, RTC_CTRL_B) & ~(RTC_CTRL_B_SET)));
  }
  
  /**

   * ds1685_rtc_get_ssn - retrieve the silicon serial number.
   * @rtc: pointer to the ds1685 rtc structure.
   * @ssn: u8 array to hold the bits of the silicon serial number.
   *
   * This number starts at 0x40, and is 8-bytes long, ending at 0x47. The
   * first byte is the model number, the next six bytes are the serial number
   * digits, and the final byte is a CRC check byte.  Together, they form the
   * silicon serial number.
   *
   * These values are stored in bank1, so ds1685_rtc_switch_to_bank1 must be
   * called first before calling this function, else data will be read out of
   * the bank0 NVRAM.  Be sure to call ds1685_rtc_switch_to_bank0 when done.
   */
  static inline void
  ds1685_rtc_get_ssn(struct ds1685_priv *rtc, u8 *ssn)
  {
  	ssn[0] = rtc->read(rtc, RTC_BANK1_SSN_MODEL);
  	ssn[1] = rtc->read(rtc, RTC_BANK1_SSN_BYTE_1);
  	ssn[2] = rtc->read(rtc, RTC_BANK1_SSN_BYTE_2);
  	ssn[3] = rtc->read(rtc, RTC_BANK1_SSN_BYTE_3);
  	ssn[4] = rtc->read(rtc, RTC_BANK1_SSN_BYTE_4);
  	ssn[5] = rtc->read(rtc, RTC_BANK1_SSN_BYTE_5);
  	ssn[6] = rtc->read(rtc, RTC_BANK1_SSN_BYTE_6);
  	ssn[7] = rtc->read(rtc, RTC_BANK1_SSN_CRC);
  }
  /* ----------------------------------------------------------------------- */
  
  
  /* ----------------------------------------------------------------------- */
  /* Read/Set Time & Alarm functions */
  
  /**
   * ds1685_rtc_read_time - reads the time registers.
   * @dev: pointer to device structure.
   * @tm: pointer to rtc_time structure.
   */
  static int
  ds1685_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {

  	struct ds1685_priv *rtc = dev_get_drvdata(dev);

  	u8 century;

  	u8 seconds, minutes, hours, wday, mday, month, years;
  
  	/* Fetch the time info from the RTC registers. */
  	ds1685_rtc_begin_data_access(rtc);
  	seconds = rtc->read(rtc, RTC_SECS);
  	minutes = rtc->read(rtc, RTC_MINS);
  	hours   = rtc->read(rtc, RTC_HRS);
  	wday    = rtc->read(rtc, RTC_WDAY);
  	mday    = rtc->read(rtc, RTC_MDAY);
  	month   = rtc->read(rtc, RTC_MONTH);
  	years   = rtc->read(rtc, RTC_YEAR);
  	century = rtc->read(rtc, RTC_CENTURY);

  	ds1685_rtc_end_data_access(rtc);
  
  	/* bcd2bin if needed, perform fixups, and store to rtc_time. */
  	years        = ds1685_rtc_bcd2bin(rtc, years, RTC_YEAR_BCD_MASK,
  					  RTC_YEAR_BIN_MASK);
  	century      = ds1685_rtc_bcd2bin(rtc, century, RTC_CENTURY_MASK,
  					  RTC_CENTURY_MASK);
  	tm->tm_sec   = ds1685_rtc_bcd2bin(rtc, seconds, RTC_SECS_BCD_MASK,
  					  RTC_SECS_BIN_MASK);
  	tm->tm_min   = ds1685_rtc_bcd2bin(rtc, minutes, RTC_MINS_BCD_MASK,
  					  RTC_MINS_BIN_MASK);
  	tm->tm_hour  = ds1685_rtc_bcd2bin(rtc, hours, RTC_HRS_24_BCD_MASK,
  					  RTC_HRS_24_BIN_MASK);
  	tm->tm_wday  = (ds1685_rtc_bcd2bin(rtc, wday, RTC_WDAY_MASK,
  					   RTC_WDAY_MASK) - 1);
  	tm->tm_mday  = ds1685_rtc_bcd2bin(rtc, mday, RTC_MDAY_BCD_MASK,
  					  RTC_MDAY_BIN_MASK);
  	tm->tm_mon   = (ds1685_rtc_bcd2bin(rtc, month, RTC_MONTH_BCD_MASK,
  					   RTC_MONTH_BIN_MASK) - 1);
  	tm->tm_year  = ((years + (century * 100)) - 1900);
  	tm->tm_yday  = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
  	tm->tm_isdst = 0; /* RTC has hardcoded timezone, so don't use. */

  	return 0;

  }
  
  /**
   * ds1685_rtc_set_time - sets the time registers.
   * @dev: pointer to device structure.
   * @tm: pointer to rtc_time structure.
   */
  static int
  ds1685_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {

  	struct ds1685_priv *rtc = dev_get_drvdata(dev);

  	u8 ctrlb, seconds, minutes, hours, wday, mday, month, years, century;
  
  	/* Fetch the time info from rtc_time. */
  	seconds = ds1685_rtc_bin2bcd(rtc, tm->tm_sec, RTC_SECS_BIN_MASK,
  				     RTC_SECS_BCD_MASK);
  	minutes = ds1685_rtc_bin2bcd(rtc, tm->tm_min, RTC_MINS_BIN_MASK,
  				     RTC_MINS_BCD_MASK);
  	hours   = ds1685_rtc_bin2bcd(rtc, tm->tm_hour, RTC_HRS_24_BIN_MASK,
  				     RTC_HRS_24_BCD_MASK);
  	wday    = ds1685_rtc_bin2bcd(rtc, (tm->tm_wday + 1), RTC_WDAY_MASK,
  				     RTC_WDAY_MASK);
  	mday    = ds1685_rtc_bin2bcd(rtc, tm->tm_mday, RTC_MDAY_BIN_MASK,
  				     RTC_MDAY_BCD_MASK);
  	month   = ds1685_rtc_bin2bcd(rtc, (tm->tm_mon + 1), RTC_MONTH_BIN_MASK,
  				     RTC_MONTH_BCD_MASK);
  	years   = ds1685_rtc_bin2bcd(rtc, (tm->tm_year % 100),
  				     RTC_YEAR_BIN_MASK, RTC_YEAR_BCD_MASK);
  	century = ds1685_rtc_bin2bcd(rtc, ((tm->tm_year + 1900) / 100),
  				     RTC_CENTURY_MASK, RTC_CENTURY_MASK);
  
  	/*
  	 * Perform Sanity Checks:
  	 *   - Months: !> 12, Month Day != 0.
  	 *   - Month Day !> Max days in current month.
  	 *   - Hours !>= 24, Mins !>= 60, Secs !>= 60, & Weekday !> 7.
  	 */
  	if ((tm->tm_mon > 11) || (mday == 0))
  		return -EDOM;
  
  	if (tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year))
  		return -EDOM;
  
  	if ((tm->tm_hour >= 24) || (tm->tm_min >= 60) ||
  	    (tm->tm_sec >= 60)  || (wday > 7))
  		return -EDOM;
  
  	/*
  	 * Set the data mode to use and store the time values in the
  	 * RTC registers.
  	 */
  	ds1685_rtc_begin_data_access(rtc);
  	ctrlb = rtc->read(rtc, RTC_CTRL_B);
  	if (rtc->bcd_mode)
  		ctrlb &= ~(RTC_CTRL_B_DM);
  	else
  		ctrlb |= RTC_CTRL_B_DM;
  	rtc->write(rtc, RTC_CTRL_B, ctrlb);
  	rtc->write(rtc, RTC_SECS, seconds);
  	rtc->write(rtc, RTC_MINS, minutes);
  	rtc->write(rtc, RTC_HRS, hours);
  	rtc->write(rtc, RTC_WDAY, wday);
  	rtc->write(rtc, RTC_MDAY, mday);
  	rtc->write(rtc, RTC_MONTH, month);
  	rtc->write(rtc, RTC_YEAR, years);
  	rtc->write(rtc, RTC_CENTURY, century);
  	ds1685_rtc_end_data_access(rtc);
  
  	return 0;
  }
  
  /**
   * ds1685_rtc_read_alarm - reads the alarm registers.
   * @dev: pointer to device structure.
   * @alrm: pointer to rtc_wkalrm structure.
   *
   * There are three primary alarm registers: seconds, minutes, and hours.
   * A fourth alarm register for the month date is also available in bank1 for
   * kickstart/wakeup features.  The DS1685/DS1687 manual states that a
   * "don't care" value ranging from 0xc0 to 0xff may be written into one or
   * more of the three alarm bytes to act as a wildcard value.  The fourth
   * byte doesn't support a "don't care" value.
   */
  static int
  ds1685_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
  {

  	struct ds1685_priv *rtc = dev_get_drvdata(dev);

  	u8 seconds, minutes, hours, mday, ctrlb, ctrlc;

  	int ret;

  
  	/* Fetch the alarm info from the RTC alarm registers. */
  	ds1685_rtc_begin_data_access(rtc);
  	seconds	= rtc->read(rtc, RTC_SECS_ALARM);
  	minutes	= rtc->read(rtc, RTC_MINS_ALARM);
  	hours	= rtc->read(rtc, RTC_HRS_ALARM);
  	mday	= rtc->read(rtc, RTC_MDAY_ALARM);
  	ctrlb	= rtc->read(rtc, RTC_CTRL_B);
  	ctrlc	= rtc->read(rtc, RTC_CTRL_C);
  	ds1685_rtc_end_data_access(rtc);

  	/* Check the month date for validity. */
  	ret = ds1685_rtc_check_mday(rtc, mday);
  	if (ret)
  		return ret;

  
  	/*
  	 * Check the three alarm bytes.
  	 *
  	 * The Linux RTC system doesn't support the "don't care" capability
  	 * of this RTC chip.  We check for it anyways in case support is

  	 * added in the future and only assign when we care.

  	 */

  	if (likely(seconds < 0xc0))

  		alrm->time.tm_sec = ds1685_rtc_bcd2bin(rtc, seconds,
  						       RTC_SECS_BCD_MASK,
  						       RTC_SECS_BIN_MASK);

  	if (likely(minutes < 0xc0))

  		alrm->time.tm_min = ds1685_rtc_bcd2bin(rtc, minutes,
  						       RTC_MINS_BCD_MASK,
  						       RTC_MINS_BIN_MASK);

  	if (likely(hours < 0xc0))

  		alrm->time.tm_hour = ds1685_rtc_bcd2bin(rtc, hours,
  							RTC_HRS_24_BCD_MASK,
  							RTC_HRS_24_BIN_MASK);
  
  	/* Write the data to rtc_wkalrm. */
  	alrm->time.tm_mday = ds1685_rtc_bcd2bin(rtc, mday, RTC_MDAY_BCD_MASK,
  						RTC_MDAY_BIN_MASK);

  	alrm->enabled = !!(ctrlb & RTC_CTRL_B_AIE);
  	alrm->pending = !!(ctrlc & RTC_CTRL_C_AF);
  
  	return 0;
  }
  
  /**
   * ds1685_rtc_set_alarm - sets the alarm in registers.
   * @dev: pointer to device structure.
   * @alrm: pointer to rtc_wkalrm structure.
   */
  static int
  ds1685_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
  {

  	struct ds1685_priv *rtc = dev_get_drvdata(dev);

  	u8 ctrlb, seconds, minutes, hours, mday;

  	int ret;

  
  	/* Fetch the alarm info and convert to BCD. */
  	seconds	= ds1685_rtc_bin2bcd(rtc, alrm->time.tm_sec,
  				     RTC_SECS_BIN_MASK,
  				     RTC_SECS_BCD_MASK);
  	minutes	= ds1685_rtc_bin2bcd(rtc, alrm->time.tm_min,
  				     RTC_MINS_BIN_MASK,
  				     RTC_MINS_BCD_MASK);
  	hours	= ds1685_rtc_bin2bcd(rtc, alrm->time.tm_hour,
  				     RTC_HRS_24_BIN_MASK,
  				     RTC_HRS_24_BCD_MASK);
  	mday	= ds1685_rtc_bin2bcd(rtc, alrm->time.tm_mday,
  				     RTC_MDAY_BIN_MASK,
  				     RTC_MDAY_BCD_MASK);
  
  	/* Check the month date for validity. */

  	ret = ds1685_rtc_check_mday(rtc, mday);
  	if (ret)
  		return ret;

  
  	/*
  	 * Check the three alarm bytes.
  	 *
  	 * The Linux RTC system doesn't support the "don't care" capability
  	 * of this RTC chip because rtc_valid_tm tries to validate every
  	 * field, and we only support four fields.  We put the support
  	 * here anyways for the future.
  	 */

  	if (unlikely(seconds >= 0xc0))

  		seconds = 0xff;

  	if (unlikely(minutes >= 0xc0))

  		minutes = 0xff;

  	if (unlikely(hours >= 0xc0))

  		hours = 0xff;
  
  	alrm->time.tm_mon	= -1;
  	alrm->time.tm_year	= -1;
  	alrm->time.tm_wday	= -1;
  	alrm->time.tm_yday	= -1;
  	alrm->time.tm_isdst	= -1;
  
  	/* Disable the alarm interrupt first. */
  	ds1685_rtc_begin_data_access(rtc);
  	ctrlb = rtc->read(rtc, RTC_CTRL_B);
  	rtc->write(rtc, RTC_CTRL_B, (ctrlb & ~(RTC_CTRL_B_AIE)));
  
  	/* Read ctrlc to clear RTC_CTRL_C_AF. */
  	rtc->read(rtc, RTC_CTRL_C);
  
  	/*
  	 * Set the data mode to use and store the time values in the
  	 * RTC registers.
  	 */
  	ctrlb = rtc->read(rtc, RTC_CTRL_B);
  	if (rtc->bcd_mode)
  		ctrlb &= ~(RTC_CTRL_B_DM);
  	else
  		ctrlb |= RTC_CTRL_B_DM;
  	rtc->write(rtc, RTC_CTRL_B, ctrlb);
  	rtc->write(rtc, RTC_SECS_ALARM, seconds);
  	rtc->write(rtc, RTC_MINS_ALARM, minutes);
  	rtc->write(rtc, RTC_HRS_ALARM, hours);
  	rtc->write(rtc, RTC_MDAY_ALARM, mday);
  
  	/* Re-enable the alarm if needed. */
  	if (alrm->enabled) {
  		ctrlb = rtc->read(rtc, RTC_CTRL_B);
  		ctrlb |= RTC_CTRL_B_AIE;
  		rtc->write(rtc, RTC_CTRL_B, ctrlb);
  	}
  
  	/* Done! */
  	ds1685_rtc_end_data_access(rtc);
  
  	return 0;
  }
  /* ----------------------------------------------------------------------- */
  
  
  /* ----------------------------------------------------------------------- */
  /* /dev/rtcX Interface functions */

  /**
   * ds1685_rtc_alarm_irq_enable - replaces ioctl() RTC_AIE on/off.
   * @dev: pointer to device structure.
   * @enabled: flag indicating whether to enable or disable.
   */
  static int
  ds1685_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
  {
  	struct ds1685_priv *rtc = dev_get_drvdata(dev);

  
  	/* Flip the requisite interrupt-enable bit. */
  	if (enabled)
  		rtc->write(rtc, RTC_CTRL_B, (rtc->read(rtc, RTC_CTRL_B) |
  					     RTC_CTRL_B_AIE));
  	else
  		rtc->write(rtc, RTC_CTRL_B, (rtc->read(rtc, RTC_CTRL_B) &
  					     ~(RTC_CTRL_B_AIE)));
  
  	/* Read Control C to clear all the flag bits. */
  	rtc->read(rtc, RTC_CTRL_C);

  
  	return 0;
  }

  /* ----------------------------------------------------------------------- */
  
  
  /* ----------------------------------------------------------------------- */

  /* IRQ handler */

  
  /**

   * ds1685_rtc_extended_irq - take care of extended interrupts
   * @rtc: pointer to the ds1685 rtc structure.
   * @pdev: platform device pointer.

   */
  static void

  ds1685_rtc_extended_irq(struct ds1685_priv *rtc, struct platform_device *pdev)

  {

  	u8 ctrl4a, ctrl4b;

  	ds1685_rtc_switch_to_bank1(rtc);
  	ctrl4a = rtc->read(rtc, RTC_EXT_CTRL_4A);
  	ctrl4b = rtc->read(rtc, RTC_EXT_CTRL_4B);
  
  	/*
  	 * Check for a kickstart interrupt. With Vcc applied, this
  	 * typically means that the power button was pressed, so we
  	 * begin the shutdown sequence.
  	 */
  	if ((ctrl4b & RTC_CTRL_4B_KSE) && (ctrl4a & RTC_CTRL_4A_KF)) {
  		/* Briefly disable kickstarts to debounce button presses. */
  		rtc->write(rtc, RTC_EXT_CTRL_4B,
  			   (rtc->read(rtc, RTC_EXT_CTRL_4B) &
  			    ~(RTC_CTRL_4B_KSE)));
  
  		/* Clear the kickstart flag. */
  		rtc->write(rtc, RTC_EXT_CTRL_4A,
  			   (ctrl4a & ~(RTC_CTRL_4A_KF)));
  
  
  		/*
  		 * Sleep 500ms before re-enabling kickstarts.  This allows
  		 * adequate time to avoid reading signal jitter as additional
  		 * button presses.
  		 */
  		msleep(500);
  		rtc->write(rtc, RTC_EXT_CTRL_4B,
  			   (rtc->read(rtc, RTC_EXT_CTRL_4B) |
  			    RTC_CTRL_4B_KSE));
  
  		/* Call the platform pre-poweroff function. Else, shutdown. */
  		if (rtc->prepare_poweroff != NULL)
  			rtc->prepare_poweroff();
  		else
  			ds1685_rtc_poweroff(pdev);
  	}
  
  	/*
  	 * Check for a wake-up interrupt.  With Vcc applied, this is
  	 * essentially a second alarm interrupt, except it takes into
  	 * account the 'date' register in bank1 in addition to the
  	 * standard three alarm registers.
  	 */
  	if ((ctrl4b & RTC_CTRL_4B_WIE) && (ctrl4a & RTC_CTRL_4A_WF)) {
  		rtc->write(rtc, RTC_EXT_CTRL_4A,
  			   (ctrl4a & ~(RTC_CTRL_4A_WF)));
  
  		/* Call the platform wake_alarm function if defined. */
  		if (rtc->wake_alarm != NULL)
  			rtc->wake_alarm();
  		else
  			dev_warn(&pdev->dev,
  				 "Wake Alarm IRQ just occurred!
  ");
  	}
  
  	/*
  	 * Check for a ram-clear interrupt.  This happens if RIE=1 and RF=0
  	 * when RCE=1 in 4B.  This clears all NVRAM bytes in bank0 by setting
  	 * each byte to a logic 1.  This has no effect on any extended
  	 * NV-SRAM that might be present, nor on the time/calendar/alarm
  	 * registers.  After a ram-clear is completed, there is a minimum
  	 * recovery time of ~150ms in which all reads/writes are locked out.
  	 * NOTE: A ram-clear can still occur if RCE=1 and RIE=0.  We cannot
  	 * catch this scenario.
  	 */
  	if ((ctrl4b & RTC_CTRL_4B_RIE) && (ctrl4a & RTC_CTRL_4A_RF)) {
  		rtc->write(rtc, RTC_EXT_CTRL_4A,
  			   (ctrl4a & ~(RTC_CTRL_4A_RF)));
  		msleep(150);
  
  		/* Call the platform post_ram_clear function if defined. */
  		if (rtc->post_ram_clear != NULL)
  			rtc->post_ram_clear();
  		else
  			dev_warn(&pdev->dev,
  				 "RAM-Clear IRQ just occurred!
  ");
  	}
  	ds1685_rtc_switch_to_bank0(rtc);

  }
  
  /**
   * ds1685_rtc_irq_handler - IRQ handler.
   * @irq: IRQ number.
   * @dev_id: platform device pointer.
   */
  static irqreturn_t
  ds1685_rtc_irq_handler(int irq, void *dev_id)
  {
  	struct platform_device *pdev = dev_id;
  	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
  	struct mutex *rtc_mutex;
  	u8 ctrlb, ctrlc;
  	unsigned long events = 0;
  	u8 num_irqs = 0;
  
  	/* Abort early if the device isn't ready yet (i.e., DEBUG_SHIRQ). */
  	if (unlikely(!rtc))
  		return IRQ_HANDLED;
  
  	rtc_mutex = &rtc->dev->ops_lock;
  	mutex_lock(rtc_mutex);
  
  	/* Ctrlb holds the interrupt-enable bits and ctrlc the flag bits. */
  	ctrlb = rtc->read(rtc, RTC_CTRL_B);
  	ctrlc = rtc->read(rtc, RTC_CTRL_C);
  
  	/* Is the IRQF bit set? */
  	if (likely(ctrlc & RTC_CTRL_C_IRQF)) {
  		/*
  		 * We need to determine if it was one of the standard
  		 * events: PF, AF, or UF.  If so, we handle them and
  		 * update the RTC core.
  		 */
  		if (likely(ctrlc & RTC_CTRL_B_PAU_MASK)) {
  			events = RTC_IRQF;
  
  			/* Check for a periodic interrupt. */
  			if ((ctrlb & RTC_CTRL_B_PIE) &&
  			    (ctrlc & RTC_CTRL_C_PF)) {
  				events |= RTC_PF;
  				num_irqs++;
  			}
  
  			/* Check for an alarm interrupt. */
  			if ((ctrlb & RTC_CTRL_B_AIE) &&
  			    (ctrlc & RTC_CTRL_C_AF)) {
  				events |= RTC_AF;
  				num_irqs++;
  			}

  			/* Check for an update interrupt. */
  			if ((ctrlb & RTC_CTRL_B_UIE) &&
  			    (ctrlc & RTC_CTRL_C_UF)) {
  				events |= RTC_UF;
  				num_irqs++;
  			}
  		} else {
  			/*
  			 * One of the "extended" interrupts was received that
  			 * is not recognized by the RTC core.
  			 */
  			ds1685_rtc_extended_irq(rtc, pdev);
  		}
  	}
  	rtc_update_irq(rtc->dev, num_irqs, events);

  	mutex_unlock(rtc_mutex);

  
  	return events ? IRQ_HANDLED : IRQ_NONE;

  }
  /* ----------------------------------------------------------------------- */
  
  
  /* ----------------------------------------------------------------------- */
  /* ProcFS interface */
  
  #ifdef CONFIG_PROC_FS
  #define NUM_REGS	6	/* Num of control registers. */
  #define NUM_BITS	8	/* Num bits per register. */
  #define NUM_SPACES	4	/* Num spaces between each bit. */
  
  /*
   * Periodic Interrupt Rates.
   */
  static const char *ds1685_rtc_pirq_rate[16] = {
  	"none", "3.90625ms", "7.8125ms", "0.122070ms", "0.244141ms",
  	"0.488281ms", "0.9765625ms", "1.953125ms", "3.90625ms", "7.8125ms",
  	"15.625ms", "31.25ms", "62.5ms", "125ms", "250ms", "500ms"
  };
  
  /*
   * Square-Wave Output Frequencies.
   */
  static const char *ds1685_rtc_sqw_freq[16] = {
  	"none", "256Hz", "128Hz", "8192Hz", "4096Hz", "2048Hz", "1024Hz",
  	"512Hz", "256Hz", "128Hz", "64Hz", "32Hz", "16Hz", "8Hz", "4Hz", "2Hz"
  };

  /**
   * ds1685_rtc_proc - procfs access function.
   * @dev: pointer to device structure.
   * @seq: pointer to seq_file structure.
   */
  static int
  ds1685_rtc_proc(struct device *dev, struct seq_file *seq)
  {

  	struct ds1685_priv *rtc = dev_get_drvdata(dev);

  	u8 ctrla, ctrlb, ctrld, ctrl4a, ctrl4b, ssn[8];

  	char *model;

  
  	/* Read all the relevant data from the control registers. */
  	ds1685_rtc_switch_to_bank1(rtc);
  	ds1685_rtc_get_ssn(rtc, ssn);
  	ctrla = rtc->read(rtc, RTC_CTRL_A);
  	ctrlb = rtc->read(rtc, RTC_CTRL_B);

  	ctrld = rtc->read(rtc, RTC_CTRL_D);
  	ctrl4a = rtc->read(rtc, RTC_EXT_CTRL_4A);
  	ctrl4b = rtc->read(rtc, RTC_EXT_CTRL_4B);
  	ds1685_rtc_switch_to_bank0(rtc);
  
  	/* Determine the RTC model. */
  	switch (ssn[0]) {
  	case RTC_MODEL_DS1685:
  		model = "DS1685/DS1687\0";
  		break;
  	case RTC_MODEL_DS1689:
  		model = "DS1689/DS1693\0";
  		break;
  	case RTC_MODEL_DS17285:
  		model = "DS17285/DS17287\0";
  		break;
  	case RTC_MODEL_DS17485:
  		model = "DS17485/DS17487\0";
  		break;
  	case RTC_MODEL_DS17885:
  		model = "DS17885/DS17887\0";
  		break;
  	default:
  		model = "Unknown\0";
  		break;
  	}
  
  	/* Print out the information. */
  	seq_printf(seq,
  	   "Model\t\t: %s
  "
  	   "Oscillator\t: %s
  "
  	   "12/24hr\t\t: %s
  "
  	   "DST\t\t: %s
  "
  	   "Data mode\t: %s
  "
  	   "Battery\t\t: %s
  "
  	   "Aux batt\t: %s
  "
  	   "Update IRQ\t: %s
  "
  	   "Periodic IRQ\t: %s
  "
  	   "Periodic Rate\t: %s
  "
  	   "SQW Freq\t: %s
  "

  	   "Serial #\t: %8phC
  ",

  	   model,
  	   ((ctrla & RTC_CTRL_A_DV1) ? "enabled" : "disabled"),
  	   ((ctrlb & RTC_CTRL_B_2412) ? "24-hour" : "12-hour"),
  	   ((ctrlb & RTC_CTRL_B_DSE) ? "enabled" : "disabled"),
  	   ((ctrlb & RTC_CTRL_B_DM) ? "binary" : "BCD"),
  	   ((ctrld & RTC_CTRL_D_VRT) ? "ok" : "exhausted or n/a"),
  	   ((ctrl4a & RTC_CTRL_4A_VRT2) ? "ok" : "exhausted or n/a"),
  	   ((ctrlb & RTC_CTRL_B_UIE) ? "yes" : "no"),
  	   ((ctrlb & RTC_CTRL_B_PIE) ? "yes" : "no"),
  	   (!(ctrl4b & RTC_CTRL_4B_E32K) ?
  	    ds1685_rtc_pirq_rate[(ctrla & RTC_CTRL_A_RS_MASK)] : "none"),
  	   (!((ctrl4b & RTC_CTRL_4B_E32K)) ?
  	    ds1685_rtc_sqw_freq[(ctrla & RTC_CTRL_A_RS_MASK)] : "32768Hz"),

  	   ssn);

  	return 0;
  }
  #else
  #define ds1685_rtc_proc NULL
  #endif /* CONFIG_PROC_FS */
  /* ----------------------------------------------------------------------- */
  
  
  /* ----------------------------------------------------------------------- */
  /* RTC Class operations */
  
  static const struct rtc_class_ops
  ds1685_rtc_ops = {
  	.proc = ds1685_rtc_proc,
  	.read_time = ds1685_rtc_read_time,
  	.set_time = ds1685_rtc_set_time,
  	.read_alarm = ds1685_rtc_read_alarm,
  	.set_alarm = ds1685_rtc_set_alarm,
  	.alarm_irq_enable = ds1685_rtc_alarm_irq_enable,
  };
  /* ----------------------------------------------------------------------- */

  static int ds1685_nvram_read(void *priv, unsigned int pos, void *val,
  			     size_t size)

  {

  	struct ds1685_priv *rtc = priv;

  	struct mutex *rtc_mutex = &rtc->dev->ops_lock;

  	ssize_t count;

  	u8 *buf = val;

  	int err;
  
  	err = mutex_lock_interruptible(rtc_mutex);
  	if (err)
  		return err;

  	ds1685_rtc_switch_to_bank0(rtc);
  
  	/* Read NVRAM in time and bank0 registers. */
  	for (count = 0; size > 0 && pos < NVRAM_TOTAL_SZ_BANK0;
  	     count++, size--) {
  		if (count < NVRAM_SZ_TIME)
  			*buf++ = rtc->read(rtc, (NVRAM_TIME_BASE + pos++));
  		else
  			*buf++ = rtc->read(rtc, (NVRAM_BANK0_BASE + pos++));
  	}
  
  #ifndef CONFIG_RTC_DRV_DS1689
  	if (size > 0) {
  		ds1685_rtc_switch_to_bank1(rtc);
  
  #ifndef CONFIG_RTC_DRV_DS1685
  		/* Enable burst-mode on DS17x85/DS17x87 */
  		rtc->write(rtc, RTC_EXT_CTRL_4A,
  			   (rtc->read(rtc, RTC_EXT_CTRL_4A) |
  			    RTC_CTRL_4A_BME));
  
  		/* We need one write to RTC_BANK1_RAM_ADDR_LSB to start
  		 * reading with burst-mode */
  		rtc->write(rtc, RTC_BANK1_RAM_ADDR_LSB,
  			   (pos - NVRAM_TOTAL_SZ_BANK0));
  #endif
  
  		/* Read NVRAM in bank1 registers. */
  		for (count = 0; size > 0 && pos < NVRAM_TOTAL_SZ;
  		     count++, size--) {
  #ifdef CONFIG_RTC_DRV_DS1685
  			/* DS1685/DS1687 has to write to RTC_BANK1_RAM_ADDR
  			 * before each read. */
  			rtc->write(rtc, RTC_BANK1_RAM_ADDR,
  				   (pos - NVRAM_TOTAL_SZ_BANK0));
  #endif
  			*buf++ = rtc->read(rtc, RTC_BANK1_RAM_DATA_PORT);
  			pos++;
  		}
  
  #ifndef CONFIG_RTC_DRV_DS1685
  		/* Disable burst-mode on DS17x85/DS17x87 */
  		rtc->write(rtc, RTC_EXT_CTRL_4A,
  			   (rtc->read(rtc, RTC_EXT_CTRL_4A) &
  			    ~(RTC_CTRL_4A_BME)));
  #endif
  		ds1685_rtc_switch_to_bank0(rtc);
  	}
  #endif /* !CONFIG_RTC_DRV_DS1689 */

  	mutex_unlock(rtc_mutex);

  	return 0;

  }

  static int ds1685_nvram_write(void *priv, unsigned int pos, void *val,
  			      size_t size)

  {

  	struct ds1685_priv *rtc = priv;

  	struct mutex *rtc_mutex = &rtc->dev->ops_lock;

  	ssize_t count;

  	u8 *buf = val;

  	int err;
  
  	err = mutex_lock_interruptible(rtc_mutex);
  	if (err)
  		return err;

  	ds1685_rtc_switch_to_bank0(rtc);
  
  	/* Write NVRAM in time and bank0 registers. */
  	for (count = 0; size > 0 && pos < NVRAM_TOTAL_SZ_BANK0;
  	     count++, size--)
  		if (count < NVRAM_SZ_TIME)
  			rtc->write(rtc, (NVRAM_TIME_BASE + pos++),
  				   *buf++);
  		else
  			rtc->write(rtc, (NVRAM_BANK0_BASE), *buf++);
  
  #ifndef CONFIG_RTC_DRV_DS1689
  	if (size > 0) {
  		ds1685_rtc_switch_to_bank1(rtc);
  
  #ifndef CONFIG_RTC_DRV_DS1685
  		/* Enable burst-mode on DS17x85/DS17x87 */
  		rtc->write(rtc, RTC_EXT_CTRL_4A,
  			   (rtc->read(rtc, RTC_EXT_CTRL_4A) |
  			    RTC_CTRL_4A_BME));
  
  		/* We need one write to RTC_BANK1_RAM_ADDR_LSB to start
  		 * writing with burst-mode */
  		rtc->write(rtc, RTC_BANK1_RAM_ADDR_LSB,
  			   (pos - NVRAM_TOTAL_SZ_BANK0));
  #endif
  
  		/* Write NVRAM in bank1 registers. */
  		for (count = 0; size > 0 && pos < NVRAM_TOTAL_SZ;
  		     count++, size--) {
  #ifdef CONFIG_RTC_DRV_DS1685
  			/* DS1685/DS1687 has to write to RTC_BANK1_RAM_ADDR
  			 * before each read. */
  			rtc->write(rtc, RTC_BANK1_RAM_ADDR,
  				   (pos - NVRAM_TOTAL_SZ_BANK0));
  #endif
  			rtc->write(rtc, RTC_BANK1_RAM_DATA_PORT, *buf++);
  			pos++;
  		}
  
  #ifndef CONFIG_RTC_DRV_DS1685
  		/* Disable burst-mode on DS17x85/DS17x87 */
  		rtc->write(rtc, RTC_EXT_CTRL_4A,
  			   (rtc->read(rtc, RTC_EXT_CTRL_4A) &
  			    ~(RTC_CTRL_4A_BME)));
  #endif
  		ds1685_rtc_switch_to_bank0(rtc);
  	}
  #endif /* !CONFIG_RTC_DRV_DS1689 */

  	mutex_unlock(rtc_mutex);

  	return 0;

  }

  /* ----------------------------------------------------------------------- */
  /* SysFS interface */

  
  /**
   * ds1685_rtc_sysfs_battery_show - sysfs file for main battery status.
   * @dev: pointer to device structure.
   * @attr: pointer to device_attribute structure.
   * @buf: pointer to char array to hold the output.
   */
  static ssize_t
  ds1685_rtc_sysfs_battery_show(struct device *dev,
  			      struct device_attribute *attr, char *buf)
  {

  	struct ds1685_priv *rtc = dev_get_drvdata(dev->parent);

  	u8 ctrld;
  
  	ctrld = rtc->read(rtc, RTC_CTRL_D);

  	return sprintf(buf, "%s
  ",

  			(ctrld & RTC_CTRL_D_VRT) ? "ok" : "not ok or N/A");
  }
  static DEVICE_ATTR(battery, S_IRUGO, ds1685_rtc_sysfs_battery_show, NULL);
  
  /**
   * ds1685_rtc_sysfs_auxbatt_show - sysfs file for aux battery status.
   * @dev: pointer to device structure.
   * @attr: pointer to device_attribute structure.
   * @buf: pointer to char array to hold the output.
   */
  static ssize_t
  ds1685_rtc_sysfs_auxbatt_show(struct device *dev,
  			      struct device_attribute *attr, char *buf)
  {

  	struct ds1685_priv *rtc = dev_get_drvdata(dev->parent);

  	u8 ctrl4a;
  
  	ds1685_rtc_switch_to_bank1(rtc);
  	ctrl4a = rtc->read(rtc, RTC_EXT_CTRL_4A);
  	ds1685_rtc_switch_to_bank0(rtc);

  	return sprintf(buf, "%s
  ",

  			(ctrl4a & RTC_CTRL_4A_VRT2) ? "ok" : "not ok or N/A");
  }
  static DEVICE_ATTR(auxbatt, S_IRUGO, ds1685_rtc_sysfs_auxbatt_show, NULL);
  
  /**
   * ds1685_rtc_sysfs_serial_show - sysfs file for silicon serial number.
   * @dev: pointer to device structure.
   * @attr: pointer to device_attribute structure.
   * @buf: pointer to char array to hold the output.
   */
  static ssize_t
  ds1685_rtc_sysfs_serial_show(struct device *dev,
  			     struct device_attribute *attr, char *buf)
  {

  	struct ds1685_priv *rtc = dev_get_drvdata(dev->parent);

  	u8 ssn[8];
  
  	ds1685_rtc_switch_to_bank1(rtc);
  	ds1685_rtc_get_ssn(rtc, ssn);
  	ds1685_rtc_switch_to_bank0(rtc);

  	return sprintf(buf, "%8phC
  ", ssn);

  }
  static DEVICE_ATTR(serial, S_IRUGO, ds1685_rtc_sysfs_serial_show, NULL);

  /*

   * struct ds1685_rtc_sysfs_misc_attrs - list for misc RTC features.
   */
  static struct attribute*
  ds1685_rtc_sysfs_misc_attrs[] = {
  	&dev_attr_battery.attr,
  	&dev_attr_auxbatt.attr,
  	&dev_attr_serial.attr,
  	NULL,
  };

  /*

   * struct ds1685_rtc_sysfs_misc_grp - attr group for misc RTC features.
   */
  static const struct attribute_group
  ds1685_rtc_sysfs_misc_grp = {
  	.name = "misc",
  	.attrs = ds1685_rtc_sysfs_misc_attrs,
  };

  /* ----------------------------------------------------------------------- */
  /* Driver Probe/Removal */
  
  /**
   * ds1685_rtc_probe - initializes rtc driver.
   * @pdev: pointer to platform_device structure.
   */
  static int
  ds1685_rtc_probe(struct platform_device *pdev)
  {
  	struct rtc_device *rtc_dev;

  	struct ds1685_priv *rtc;
  	struct ds1685_rtc_platform_data *pdata;
  	u8 ctrla, ctrlb, hours;
  	unsigned char am_pm;
  	int ret = 0;

  	struct nvmem_config nvmem_cfg = {
  		.name = "ds1685_nvram",
  		.size = NVRAM_TOTAL_SZ,
  		.reg_read = ds1685_nvram_read,
  		.reg_write = ds1685_nvram_write,
  	};

  
  	/* Get the platform data. */
  	pdata = (struct ds1685_rtc_platform_data *) pdev->dev.platform_data;
  	if (!pdata)
  		return -ENODEV;
  
  	/* Allocate memory for the rtc device. */
  	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
  	if (!rtc)
  		return -ENOMEM;

  	/* Setup resources and access functions */
  	switch (pdata->access_type) {
  	case ds1685_reg_direct:
  		rtc->regs = devm_platform_ioremap_resource(pdev, 0);
  		if (IS_ERR(rtc->regs))
  			return PTR_ERR(rtc->regs);
  		rtc->read = ds1685_read;
  		rtc->write = ds1685_write;
  		break;
  	case ds1685_reg_indirect:

  		rtc->regs = devm_platform_ioremap_resource(pdev, 0);
  		if (IS_ERR(rtc->regs))
  			return PTR_ERR(rtc->regs);

  		rtc->data = devm_platform_ioremap_resource(pdev, 1);
  		if (IS_ERR(rtc->data))
  			return PTR_ERR(rtc->data);
  		rtc->read = ds1685_indirect_read;
  		rtc->write = ds1685_indirect_write;
  		break;

  	}

  	if (!rtc->read || !rtc->write)
  		return -ENXIO;

  	/* Get the register step size. */
  	if (pdata->regstep > 0)
  		rtc->regstep = pdata->regstep;
  	else
  		rtc->regstep = 1;

  	/* Platform pre-shutdown function, if defined. */
  	if (pdata->plat_prepare_poweroff)
  		rtc->prepare_poweroff = pdata->plat_prepare_poweroff;
  
  	/* Platform wake_alarm function, if defined. */
  	if (pdata->plat_wake_alarm)
  		rtc->wake_alarm = pdata->plat_wake_alarm;
  
  	/* Platform post_ram_clear function, if defined. */
  	if (pdata->plat_post_ram_clear)
  		rtc->post_ram_clear = pdata->plat_post_ram_clear;

  	/* set the driver data. */

  	platform_set_drvdata(pdev, rtc);
  
  	/* Turn the oscillator on if is not already on (DV1 = 1). */
  	ctrla = rtc->read(rtc, RTC_CTRL_A);
  	if (!(ctrla & RTC_CTRL_A_DV1))
  		ctrla |= RTC_CTRL_A_DV1;
  
  	/* Enable the countdown chain (DV2 = 0) */
  	ctrla &= ~(RTC_CTRL_A_DV2);
  
  	/* Clear RS3-RS0 in Control A. */
  	ctrla &= ~(RTC_CTRL_A_RS_MASK);
  
  	/*
  	 * All done with Control A.  Switch to Bank 1 for the remainder of
  	 * the RTC setup so we have access to the extended functions.
  	 */
  	ctrla |= RTC_CTRL_A_DV0;
  	rtc->write(rtc, RTC_CTRL_A, ctrla);
  
  	/* Default to 32768kHz output. */
  	rtc->write(rtc, RTC_EXT_CTRL_4B,
  		   (rtc->read(rtc, RTC_EXT_CTRL_4B) | RTC_CTRL_4B_E32K));
  
  	/* Set the SET bit in Control B so we can do some housekeeping. */
  	rtc->write(rtc, RTC_CTRL_B,
  		   (rtc->read(rtc, RTC_CTRL_B) | RTC_CTRL_B_SET));
  
  	/* Read Ext Ctrl 4A and check the INCR bit to avoid a lockout. */
  	while (rtc->read(rtc, RTC_EXT_CTRL_4A) & RTC_CTRL_4A_INCR)
  		cpu_relax();
  
  	/*
  	 * If the platform supports BCD mode, then set DM=0 in Control B.
  	 * Otherwise, set DM=1 for BIN mode.
  	 */
  	ctrlb = rtc->read(rtc, RTC_CTRL_B);
  	if (pdata->bcd_mode)
  		ctrlb &= ~(RTC_CTRL_B_DM);
  	else
  		ctrlb |= RTC_CTRL_B_DM;
  	rtc->bcd_mode = pdata->bcd_mode;
  
  	/*
  	 * Disable Daylight Savings Time (DSE = 0).
  	 * The RTC has hardcoded timezone information that is rendered
  	 * obselete.  We'll let the OS deal with DST settings instead.
  	 */
  	if (ctrlb & RTC_CTRL_B_DSE)
  		ctrlb &= ~(RTC_CTRL_B_DSE);
  
  	/* Force 24-hour mode (2412 = 1). */
  	if (!(ctrlb & RTC_CTRL_B_2412)) {
  		/* Reinitialize the time hours. */
  		hours = rtc->read(rtc, RTC_HRS);
  		am_pm = hours & RTC_HRS_AMPM_MASK;
  		hours = ds1685_rtc_bcd2bin(rtc, hours, RTC_HRS_12_BCD_MASK,
  					   RTC_HRS_12_BIN_MASK);
  		hours = ((hours == 12) ? 0 : ((am_pm) ? hours + 12 : hours));
  
  		/* Enable 24-hour mode. */
  		ctrlb |= RTC_CTRL_B_2412;
  
  		/* Write back to Control B, including DM & DSE bits. */
  		rtc->write(rtc, RTC_CTRL_B, ctrlb);
  
  		/* Write the time hours back. */
  		rtc->write(rtc, RTC_HRS,
  			   ds1685_rtc_bin2bcd(rtc, hours,
  					      RTC_HRS_24_BIN_MASK,
  					      RTC_HRS_24_BCD_MASK));
  
  		/* Reinitialize the alarm hours. */
  		hours = rtc->read(rtc, RTC_HRS_ALARM);
  		am_pm = hours & RTC_HRS_AMPM_MASK;
  		hours = ds1685_rtc_bcd2bin(rtc, hours, RTC_HRS_12_BCD_MASK,
  					   RTC_HRS_12_BIN_MASK);
  		hours = ((hours == 12) ? 0 : ((am_pm) ? hours + 12 : hours));
  
  		/* Write the alarm hours back. */
  		rtc->write(rtc, RTC_HRS_ALARM,
  			   ds1685_rtc_bin2bcd(rtc, hours,
  					      RTC_HRS_24_BIN_MASK,
  					      RTC_HRS_24_BCD_MASK));
  	} else {
  		/* 24-hour mode is already set, so write Control B back. */
  		rtc->write(rtc, RTC_CTRL_B, ctrlb);
  	}
  
  	/* Unset the SET bit in Control B so the RTC can update. */
  	rtc->write(rtc, RTC_CTRL_B,
  		   (rtc->read(rtc, RTC_CTRL_B) & ~(RTC_CTRL_B_SET)));
  
  	/* Check the main battery. */
  	if (!(rtc->read(rtc, RTC_CTRL_D) & RTC_CTRL_D_VRT))
  		dev_warn(&pdev->dev,
  			 "Main battery is exhausted! RTC may be invalid!
  ");
  
  	/* Check the auxillary battery.  It is optional. */
  	if (!(rtc->read(rtc, RTC_EXT_CTRL_4A) & RTC_CTRL_4A_VRT2))
  		dev_warn(&pdev->dev,
  			 "Aux battery is exhausted or not available.
  ");
  
  	/* Read Ctrl B and clear PIE/AIE/UIE. */
  	rtc->write(rtc, RTC_CTRL_B,
  		   (rtc->read(rtc, RTC_CTRL_B) & ~(RTC_CTRL_B_PAU_MASK)));
  
  	/* Reading Ctrl C auto-clears PF/AF/UF. */
  	rtc->read(rtc, RTC_CTRL_C);
  
  	/* Read Ctrl 4B and clear RIE/WIE/KSE. */
  	rtc->write(rtc, RTC_EXT_CTRL_4B,
  		   (rtc->read(rtc, RTC_EXT_CTRL_4B) & ~(RTC_CTRL_4B_RWK_MASK)));
  
  	/* Clear RF/WF/KF in Ctrl 4A. */
  	rtc->write(rtc, RTC_EXT_CTRL_4A,
  		   (rtc->read(rtc, RTC_EXT_CTRL_4A) & ~(RTC_CTRL_4A_RWK_MASK)));
  
  	/*
  	 * Re-enable KSE to handle power button events.  We do not enable
  	 * WIE or RIE by default.
  	 */
  	rtc->write(rtc, RTC_EXT_CTRL_4B,
  		   (rtc->read(rtc, RTC_EXT_CTRL_4B) | RTC_CTRL_4B_KSE));

  	rtc_dev = devm_rtc_allocate_device(&pdev->dev);
  	if (IS_ERR(rtc_dev))
  		return PTR_ERR(rtc_dev);
  
  	rtc_dev->ops = &ds1685_rtc_ops;

  	/* Century bit is useless because leap year fails in 1900 and 2100 */
  	rtc_dev->range_min = RTC_TIMESTAMP_BEGIN_2000;
  	rtc_dev->range_max = RTC_TIMESTAMP_END_2099;

  	/* Maximum periodic rate is 8192Hz (0.122070ms). */
  	rtc_dev->max_user_freq = RTC_MAX_USER_FREQ;
  
  	/* See if the platform doesn't support UIE. */
  	if (pdata->uie_unsupported)
  		rtc_dev->uie_unsupported = 1;

  
  	rtc->dev = rtc_dev;

  	/*
  	 * Fetch the IRQ and setup the interrupt handler.
  	 *
  	 * Not all platforms have the IRQF pin tied to something.  If not, the
  	 * RTC will still set the *IE / *F flags and raise IRQF in ctrlc, but
  	 * there won't be an automatic way of notifying the kernel about it,
  	 * unless ctrlc is explicitly polled.
  	 */
  	if (!pdata->no_irq) {
  		ret = platform_get_irq(pdev, 0);

  		if (ret <= 0)

  			return ret;

  
  		rtc->irq_num = ret;
  
  		/* Request an IRQ. */
  		ret = devm_request_threaded_irq(&pdev->dev, rtc->irq_num,
  				       NULL, ds1685_rtc_irq_handler,
  				       IRQF_SHARED | IRQF_ONESHOT,
  				       pdev->name, pdev);
  
  		/* Check to see if something came back. */
  		if (unlikely(ret)) {
  			dev_warn(&pdev->dev,
  				 "RTC interrupt not available
  ");
  			rtc->irq_num = 0;
  		}

  	}
  	rtc->no_irq = pdata->no_irq;
  
  	/* Setup complete. */
  	ds1685_rtc_switch_to_bank0(rtc);

  	ret = rtc_add_group(rtc_dev, &ds1685_rtc_sysfs_misc_grp);

  	if (ret)

  		return ret;

  	rtc_dev->nvram_old_abi = true;
  	nvmem_cfg.priv = rtc;
  	ret = rtc_nvmem_register(rtc_dev, &nvmem_cfg);
  	if (ret)
  		return ret;

  	return rtc_register_device(rtc_dev);

  }
  
  /**
   * ds1685_rtc_remove - removes rtc driver.
   * @pdev: pointer to platform_device structure.
   */
  static int
  ds1685_rtc_remove(struct platform_device *pdev)
  {
  	struct ds1685_priv *rtc = platform_get_drvdata(pdev);

  	/* Read Ctrl B and clear PIE/AIE/UIE. */
  	rtc->write(rtc, RTC_CTRL_B,
  		   (rtc->read(rtc, RTC_CTRL_B) &
  		    ~(RTC_CTRL_B_PAU_MASK)));
  
  	/* Reading Ctrl C auto-clears PF/AF/UF. */
  	rtc->read(rtc, RTC_CTRL_C);
  
  	/* Read Ctrl 4B and clear RIE/WIE/KSE. */
  	rtc->write(rtc, RTC_EXT_CTRL_4B,
  		   (rtc->read(rtc, RTC_EXT_CTRL_4B) &
  		    ~(RTC_CTRL_4B_RWK_MASK)));
  
  	/* Manually clear RF/WF/KF in Ctrl 4A. */
  	rtc->write(rtc, RTC_EXT_CTRL_4A,
  		   (rtc->read(rtc, RTC_EXT_CTRL_4A) &
  		    ~(RTC_CTRL_4A_RWK_MASK)));

  	return 0;
  }

  /*

   * ds1685_rtc_driver - rtc driver properties.
   */
  static struct platform_driver ds1685_rtc_driver = {
  	.driver		= {
  		.name	= "rtc-ds1685",

  	},
  	.probe		= ds1685_rtc_probe,
  	.remove		= ds1685_rtc_remove,
  };

  module_platform_driver(ds1685_rtc_driver);

  /* ----------------------------------------------------------------------- */
  
  
  /* ----------------------------------------------------------------------- */
  /* Poweroff function */
  
  /**
   * ds1685_rtc_poweroff - uses the RTC chip to power the system off.
   * @pdev: pointer to platform_device structure.
   */

  void __noreturn

  ds1685_rtc_poweroff(struct platform_device *pdev)
  {
  	u8 ctrla, ctrl4a, ctrl4b;
  	struct ds1685_priv *rtc;
  
  	/* Check for valid RTC data, else, spin forever. */
  	if (unlikely(!pdev)) {

  		pr_emerg("platform device data not available, spinning forever ...
  ");

  		while(1);

  		unreachable();
  	} else {
  		/* Get the rtc data. */
  		rtc = platform_get_drvdata(pdev);
  
  		/*
  		 * Disable our IRQ.  We're powering down, so we're not
  		 * going to worry about cleaning up.  Most of that should
  		 * have been taken care of by the shutdown scripts and this
  		 * is the final function call.
  		 */
  		if (!rtc->no_irq)
  			disable_irq_nosync(rtc->irq_num);
  
  		/* Oscillator must be on and the countdown chain enabled. */
  		ctrla = rtc->read(rtc, RTC_CTRL_A);
  		ctrla |= RTC_CTRL_A_DV1;
  		ctrla &= ~(RTC_CTRL_A_DV2);
  		rtc->write(rtc, RTC_CTRL_A, ctrla);
  
  		/*
  		 * Read Control 4A and check the status of the auxillary
  		 * battery.  This must be present and working (VRT2 = 1)
  		 * for wakeup and kickstart functionality to be useful.
  		 */
  		ds1685_rtc_switch_to_bank1(rtc);
  		ctrl4a = rtc->read(rtc, RTC_EXT_CTRL_4A);
  		if (ctrl4a & RTC_CTRL_4A_VRT2) {
  			/* Clear all of the interrupt flags on Control 4A. */
  			ctrl4a &= ~(RTC_CTRL_4A_RWK_MASK);
  			rtc->write(rtc, RTC_EXT_CTRL_4A, ctrl4a);
  
  			/*
  			 * The auxillary battery is present and working.
  			 * Enable extended functions (ABE=1), enable
  			 * wake-up (WIE=1), and enable kickstart (KSE=1)
  			 * in Control 4B.
  			 */
  			ctrl4b = rtc->read(rtc, RTC_EXT_CTRL_4B);
  			ctrl4b |= (RTC_CTRL_4B_ABE | RTC_CTRL_4B_WIE |
  				   RTC_CTRL_4B_KSE);
  			rtc->write(rtc, RTC_EXT_CTRL_4B, ctrl4b);
  		}
  
  		/* Set PAB to 1 in Control 4A to power the system down. */
  		dev_warn(&pdev->dev, "Powerdown.
  ");
  		msleep(20);
  		rtc->write(rtc, RTC_EXT_CTRL_4A,
  			   (ctrl4a | RTC_CTRL_4A_PAB));
  
  		/* Spin ... we do not switch back to bank0. */

  		while(1);

  		unreachable();
  	}
  }
  EXPORT_SYMBOL(ds1685_rtc_poweroff);
  /* ----------------------------------------------------------------------- */
  
  
  MODULE_AUTHOR("Joshua Kinard <kumba@gentoo.org>");
  MODULE_AUTHOR("Matthias Fuchs <matthias.fuchs@esd-electronics.com>");
  MODULE_DESCRIPTION("Dallas/Maxim DS1685/DS1687-series RTC driver");
  MODULE_LICENSE("GPL");

  MODULE_ALIAS("platform:rtc-ds1685");