rtc: add driver for DS1685 family of real time clocks

This adds a driver for the Dallas/Maxim DS1685-family of RTC chips.  It
supports the DS1685/DS1687, DS1688/DS1691, DS1689/DS1693, DS17285/DS17287,
DS17485/DS17487, and DS17885/DS17887 RTC chips.  These chips are commonly
found in SGI O2 and SGI Octane systems.  It was originally derived from a
driver patch submitted by Matthias Fuchs many years ago for use in
EPPC-405-UC modules, which also used these RTCs.  In addition to the
time-keeping functions, this RTC also handles the shutdown mechanism of
the O2 and Octane and acts as a partial NVRAM for the boot PROMS in these
systems.

Verified on both an SGI O2 and an SGI Octane.

Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2252 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ds1685.c b/drivers/rtc/rtc-ds1685.c
new file mode 100644
index 000000000000..8c3bfcb115b7
--- /dev/null
+++ b/drivers/rtc/rtc-ds1685.c
@@ -0,0 +1,2252 @@
+/*
+ * 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.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#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
+
+#define DRV_VERSION	"0.42.0"
+
+
+/* ----------------------------------------------------------------------- */
+/* Standard read/write functions if platform does not provide overrides */
+
+/**
+ * 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)));
+}
+/* ----------------------------------------------------------------------- */
+
+
+/* ----------------------------------------------------------------------- */
+/* 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);
+}
+
+/**
+ * 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_begin_ctrl_access - prepare the rtc for ctrl access.
+ * @rtc: pointer to the ds1685 rtc structure.
+ * @flags: irq flags variable for spin_lock_irqsave.
+ *
+ * This takes several steps to prepare the rtc for access to read just the
+ * control registers:
+ *  - Sets a spinlock on the rtc IRQ.
+ *  - Switches the rtc to bank 1.  This allows access to the two extended
+ *    control registers.
+ *
+ * Only use this where you are certain another lock will not be held.
+ */
+static inline void
+ds1685_rtc_begin_ctrl_access(struct ds1685_priv *rtc, unsigned long flags)
+{
+	spin_lock_irqsave(&rtc->lock, flags);
+	ds1685_rtc_switch_to_bank1(rtc);
+}
+
+/**
+ * ds1685_rtc_end_ctrl_access - end ctrl access on the rtc.
+ * @rtc: pointer to the ds1685 rtc structure.
+ * @flags: irq flags variable for spin_unlock_irqrestore.
+ *
+ * This ends what was started by ds1685_rtc_begin_ctrl_access:
+ *  - Switches the rtc back to bank 0.
+ *  - Unsets the spinlock on the rtc IRQ.
+ */
+static inline void
+ds1685_rtc_end_ctrl_access(struct ds1685_priv *rtc, unsigned long flags)
+{
+	ds1685_rtc_switch_to_bank0(rtc);
+	spin_unlock_irqrestore(&rtc->lock, flags);
+}
+
+/**
+ * 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 platform_device *pdev = to_platform_device(dev);
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	u8 ctrlb, 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);
+	ctrlb   = rtc->read(rtc, RTC_CTRL_B);
+	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 rtc_valid_tm(tm);
+}
+
+/**
+ * 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 platform_device *pdev = to_platform_device(dev);
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	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 platform_device *pdev = to_platform_device(dev);
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	u8 seconds, minutes, hours, mday, ctrlb, ctrlc;
+
+	/* 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 month date. */
+	if (!(mday >= 1) && (mday <= 31))
+		return -EDOM;
+
+	/*
+	 * 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.
+	 */
+	if (unlikely((seconds >= 0xc0) && (seconds <= 0xff)))
+		alrm->time.tm_sec = -1;
+	else
+		alrm->time.tm_sec = ds1685_rtc_bcd2bin(rtc, seconds,
+						       RTC_SECS_BCD_MASK,
+						       RTC_SECS_BIN_MASK);
+
+	if (unlikely((minutes >= 0xc0) && (minutes <= 0xff)))
+		alrm->time.tm_min = -1;
+	else
+		alrm->time.tm_min = ds1685_rtc_bcd2bin(rtc, minutes,
+						       RTC_MINS_BCD_MASK,
+						       RTC_MINS_BIN_MASK);
+
+	if (unlikely((hours >= 0xc0) && (hours <= 0xff)))
+		alrm->time.tm_hour = -1;
+	else
+		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->time.tm_mon = -1;
+	alrm->time.tm_year = -1;
+	alrm->time.tm_wday = -1;
+	alrm->time.tm_yday = -1;
+	alrm->time.tm_isdst = -1;
+	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 platform_device *pdev = to_platform_device(dev);
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	u8 ctrlb, seconds, minutes, hours, mday;
+
+	/* 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. */
+	if (!(mday >= 1) && (mday <= 31))
+		return -EDOM;
+
+	/*
+	 * 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)))
+		seconds = 0xff;
+
+	if (unlikely((minutes >= 0xc0) && (minutes <= 0xff)))
+		minutes = 0xff;
+
+	if (unlikely((hours >= 0xc0) && (hours <= 0xff)))
+		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 */
+
+#ifdef CONFIG_RTC_INTF_DEV
+/**
+ * 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);
+	unsigned long flags = 0;
+
+	/* Enable/disable the Alarm IRQ-Enable flag. */
+	spin_lock_irqsave(&rtc->lock, flags);
+
+	/* 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);
+	spin_unlock_irqrestore(&rtc->lock, flags);
+
+	return 0;
+}
+#endif
+/* ----------------------------------------------------------------------- */
+
+
+/* ----------------------------------------------------------------------- */
+/* IRQ handler & workqueue. */
+
+/**
+ * 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);
+	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;
+
+	/* Ctrlb holds the interrupt-enable bits and ctrlc the flag bits. */
+	spin_lock(&rtc->lock);
+	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++;
+			}
+
+			rtc_update_irq(rtc->dev, num_irqs, events);
+		} else {
+			/*
+			 * One of the "extended" interrupts was received that
+			 * is not recognized by the RTC core.  These need to
+			 * be handled in task context as they can call other
+			 * functions and the time spent in irq context needs
+			 * to be minimized.  Schedule them into a workqueue
+			 * and inform the RTC core that the IRQs were handled.
+			 */
+			spin_unlock(&rtc->lock);
+			schedule_work(&rtc->work);
+			rtc_update_irq(rtc->dev, 0, 0);
+			return IRQ_HANDLED;
+		}
+	}
+	spin_unlock(&rtc->lock);
+
+	return events ? IRQ_HANDLED : IRQ_NONE;
+}
+
+/**
+ * ds1685_rtc_work_queue - work queue handler.
+ * @work: work_struct containing data to work on in task context.
+ */
+static void
+ds1685_rtc_work_queue(struct work_struct *work)
+{
+	struct ds1685_priv *rtc = container_of(work,
+					       struct ds1685_priv, work);
+	struct platform_device *pdev = to_platform_device(&rtc->dev->dev);
+	struct mutex *rtc_mutex = &rtc->dev->ops_lock;
+	u8 ctrl4a, ctrl4b;
+
+	mutex_lock(rtc_mutex);
+
+	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!\n");
+	}
+
+	/*
+	 * 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!\n");
+	}
+	ds1685_rtc_switch_to_bank0(rtc);
+
+	mutex_unlock(rtc_mutex);
+}
+/* ----------------------------------------------------------------------- */
+
+
+/* ----------------------------------------------------------------------- */
+/* 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"
+};
+
+#ifdef CONFIG_RTC_DS1685_PROC_REGS
+/**
+ * ds1685_rtc_print_regs - helper function to print register values.
+ * @hex: hex byte to convert into binary bits.
+ * @dest: destination char array.
+ *
+ * This is basically a hex->binary function, just with extra spacing between
+ * the digits.  It only works on 1-byte values (8 bits).
+ */
+static char*
+ds1685_rtc_print_regs(u8 hex, char *dest)
+{
+	u32 i, j;
+	char *tmp = dest;
+
+	for (i = 0; i < NUM_BITS; i++) {
+		*tmp++ = ((hex & 0x80) != 0 ? '1' : '0');
+		for (j = 0; j < NUM_SPACES; j++)
+			*tmp++ = ' ';
+		hex <<= 1;
+	}
+	*tmp++ = '\0';
+
+	return dest;
+}
+#endif
+
+/**
+ * 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 platform_device *pdev = to_platform_device(dev);
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	u8 ctrla, ctrlb, ctrlc, ctrld, ctrl4a, ctrl4b, ssn[8];
+	char *model = '\0';
+#ifdef CONFIG_RTC_DS1685_PROC_REGS
+	char bits[NUM_REGS][(NUM_BITS * NUM_SPACES) + NUM_BITS + 1];
+#endif
+
+	/* 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);
+	ctrlc = rtc->read(rtc, RTC_CTRL_C);
+	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\n"
+	   "Oscillator\t: %s\n"
+	   "12/24hr\t\t: %s\n"
+	   "DST\t\t: %s\n"
+	   "Data mode\t: %s\n"
+	   "Battery\t\t: %s\n"
+	   "Aux batt\t: %s\n"
+	   "Update IRQ\t: %s\n"
+	   "Periodic IRQ\t: %s\n"
+	   "Periodic Rate\t: %s\n"
+	   "SQW Freq\t: %s\n"
+#ifdef CONFIG_RTC_DS1685_PROC_REGS
+	   "Serial #\t: %02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x\n"
+	   "Register Status\t:\n"
+	   "   Ctrl A\t: UIP  DV2  DV1  DV0  RS3  RS2  RS1  RS0\n"
+	   "\t\t:  %s\n"
+	   "   Ctrl B\t: SET  PIE  AIE  UIE  SQWE  DM  2412 DSE\n"
+	   "\t\t:  %s\n"
+	   "   Ctrl C\t: IRQF  PF   AF   UF  ---  ---  ---  ---\n"
+	   "\t\t:  %s\n"
+	   "   Ctrl D\t: VRT  ---  ---  ---  ---  ---  ---  ---\n"
+	   "\t\t:  %s\n"
+#if !defined(CONFIG_RTC_DRV_DS1685) && !defined(CONFIG_RTC_DRV_DS1689)
+	   "   Ctrl 4A\t: VRT2 INCR BME  ---  PAB   RF   WF   KF\n"
+#else
+	   "   Ctrl 4A\t: VRT2 INCR ---  ---  PAB   RF   WF   KF\n"
+#endif
+	   "\t\t:  %s\n"
+	   "   Ctrl 4B\t: ABE  E32k  CS  RCE  PRS  RIE  WIE  KSE\n"
+	   "\t\t:  %s\n",
+#else
+	   "Serial #\t: %02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x\n",
+#endif
+	   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"),
+#ifdef CONFIG_RTC_DS1685_PROC_REGS
+	   ssn[0], ssn[1], ssn[2], ssn[3], ssn[4], ssn[5], ssn[6], ssn[7],
+	   ds1685_rtc_print_regs(ctrla, bits[0]),
+	   ds1685_rtc_print_regs(ctrlb, bits[1]),
+	   ds1685_rtc_print_regs(ctrlc, bits[2]),
+	   ds1685_rtc_print_regs(ctrld, bits[3]),
+	   ds1685_rtc_print_regs(ctrl4a, bits[4]),
+	   ds1685_rtc_print_regs(ctrl4b, bits[5]));
+#else
+	   ssn[0], ssn[1], ssn[2], ssn[3], ssn[4], ssn[5], ssn[6], ssn[7]);
+#endif
+	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,
+};
+/* ----------------------------------------------------------------------- */
+
+
+/* ----------------------------------------------------------------------- */
+/* SysFS interface */
+
+#ifdef CONFIG_SYSFS
+/**
+ * ds1685_rtc_sysfs_nvram_read - reads rtc nvram via sysfs.
+ * @file: pointer to file structure.
+ * @kobj: pointer to kobject structure.
+ * @bin_attr: pointer to bin_attribute structure.
+ * @buf: pointer to char array to hold the output.
+ * @pos: current file position pointer.
+ * @size: size of the data to read.
+ */
+static ssize_t
+ds1685_rtc_sysfs_nvram_read(struct file *filp, struct kobject *kobj,
+			    struct bin_attribute *bin_attr, char *buf,
+			    loff_t pos, size_t size)
+{
+	struct platform_device *pdev =
+		to_platform_device(container_of(kobj, struct device, kobj));
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	ssize_t count;
+	unsigned long flags = 0;
+
+	spin_lock_irqsave(&rtc->lock, flags);
+	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 */
+	spin_unlock_irqrestore(&rtc->lock, flags);
+
+	/*
+	 * XXX: Bug? this appears to cause the function to get executed
+	 * several times in succession.  But it's the only way to actually get
+	 * data written out to a file.
+	 */
+	return count;
+}
+
+/**
+ * ds1685_rtc_sysfs_nvram_write - writes rtc nvram via sysfs.
+ * @file: pointer to file structure.
+ * @kobj: pointer to kobject structure.
+ * @bin_attr: pointer to bin_attribute structure.
+ * @buf: pointer to char array to hold the input.
+ * @pos: current file position pointer.
+ * @size: size of the data to write.
+ */
+static ssize_t
+ds1685_rtc_sysfs_nvram_write(struct file *filp, struct kobject *kobj,
+			     struct bin_attribute *bin_attr, char *buf,
+			     loff_t pos, size_t size)
+{
+	struct platform_device *pdev =
+		to_platform_device(container_of(kobj, struct device, kobj));
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	ssize_t count;
+	unsigned long flags = 0;
+
+	spin_lock_irqsave(&rtc->lock, flags);
+	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 */
+	spin_unlock_irqrestore(&rtc->lock, flags);
+
+	return count;
+}
+
+/**
+ * struct ds1685_rtc_sysfs_nvram_attr - sysfs attributes for rtc nvram.
+ * @attr: nvram attributes.
+ * @read: nvram read function.
+ * @write: nvram write function.
+ * @size: nvram total size (bank0 + extended).
+ */
+static struct bin_attribute
+ds1685_rtc_sysfs_nvram_attr = {
+	.attr = {
+		.name = "nvram",
+		.mode = S_IRUGO | S_IWUSR,
+	},
+	.read = ds1685_rtc_sysfs_nvram_read,
+	.write = ds1685_rtc_sysfs_nvram_write,
+	.size = NVRAM_TOTAL_SZ
+};
+
+/**
+ * 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 platform_device *pdev = to_platform_device(dev);
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	u8 ctrld;
+
+	ctrld = rtc->read(rtc, RTC_CTRL_D);
+
+	return snprintf(buf, 13, "%s\n",
+			(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 platform_device *pdev = to_platform_device(dev);
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	u8 ctrl4a;
+
+	ds1685_rtc_switch_to_bank1(rtc);
+	ctrl4a = rtc->read(rtc, RTC_EXT_CTRL_4A);
+	ds1685_rtc_switch_to_bank0(rtc);
+
+	return snprintf(buf, 13, "%s\n",
+			(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 platform_device *pdev = to_platform_device(dev);
+	struct ds1685_priv *rtc = platform_get_drvdata(pdev);
+	u8 ssn[8];
+
+	ds1685_rtc_switch_to_bank1(rtc);
+	ds1685_rtc_get_ssn(rtc, ssn);
+	ds1685_rtc_switch_to_bank0(rtc);
+
+	return snprintf(buf, 24, "%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x\n",
+			ssn[0], ssn[1], ssn[2], ssn[3], ssn[4], ssn[5],
+			ssn[6], ssn[7]);
+
+	return 0;
+}
+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,
+};
+
+#ifdef CONFIG_RTC_DS1685_SYSFS_REGS
+/**
+ * struct ds1685_rtc_ctrl_regs.
+ * @name: char pointer for the bit name.
+ * @reg: control register the bit is in.
+ * @bit: the bit's offset in the register.
+ */
+struct ds1685_rtc_ctrl_regs {
+	const char *name;
+	const u8 reg;
+	const u8 bit;
+};
+
+/*
+ * Ctrl register bit lookup table.
+ */
+static const struct ds1685_rtc_ctrl_regs
+ds1685_ctrl_regs_table[] = {
+	{ "uip",  RTC_CTRL_A,      RTC_CTRL_A_UIP   },
+	{ "dv2",  RTC_CTRL_A,      RTC_CTRL_A_DV2   },
+	{ "dv1",  RTC_CTRL_A,      RTC_CTRL_A_DV1   },
+	{ "dv0",  RTC_CTRL_A,      RTC_CTRL_A_DV0   },
+	{ "rs3",  RTC_CTRL_A,      RTC_CTRL_A_RS3   },
+	{ "rs2",  RTC_CTRL_A,      RTC_CTRL_A_RS2   },
+	{ "rs1",  RTC_CTRL_A,      RTC_CTRL_A_RS1   },
+	{ "rs0",  RTC_CTRL_A,      RTC_CTRL_A_RS0   },
+	{ "set",  RTC_CTRL_B,      RTC_CTRL_B_SET   },
+	{ "pie",  RTC_CTRL_B,      RTC_CTRL_B_PIE   },
+	{ "aie",  RTC_CTRL_B,      RTC_CTRL_B_AIE   },
+	{ "uie",  RTC_CTRL_B,      RTC_CTRL_B_UIE   },
+	{ "sqwe", RTC_CTRL_B,      RTC_CTRL_B_SQWE  },
+	{ "dm",   RTC_CTRL_B,      RTC_CTRL_B_DM    },
+	{ "2412", RTC_CTRL_B,      RTC_CTRL_B_2412  },
+	{ "dse",  RTC_CTRL_B,      RTC_CTRL_B_DSE   },
+	{ "irqf", RTC_CTRL_C,      RTC_CTRL_C_IRQF  },
+	{ "pf",   RTC_CTRL_C,      RTC_CTRL_C_PF    },
+	{ "af",   RTC_CTRL_C,      RTC_CTRL_C_AF    },
+	{ "uf",   RTC_CTRL_C,      RTC_CTRL_C_UF    },
+	{ "vrt",  RTC_CTRL_D,      RTC_CTRL_D_VRT   },
+	{ "vrt2", RTC_EXT_CTRL_4A, RTC_CTRL_4A_VRT2 },
+	{ "incr", RTC_EXT_CTRL_4A, RTC_CTRL_4A_INCR },
+	{ "pab",  RTC_EXT_CTRL_4A, RTC_CTRL_4A_PAB  },
+	{ "rf",   RTC_EXT_CTRL_4A, RTC_CTRL_4A_RF   },
+	{ "wf",   RTC_EXT_CTRL_4A, RTC_CTRL_4A_WF   },
+	{ "kf",   RTC_EXT_CTRL_4A, RTC_CTRL_4A_KF   },
+#if !defined(CONFIG_RTC_DRV_DS1685) && !defined(CONFIG_RTC_DRV_DS1689)
+	{ "bme",  RTC_EXT_CTRL_4A, RTC_CTRL_4A_BME  },
+#endif
+	{ "abe",  RTC_EXT_CTRL_4B, RTC_CTRL_4B_ABE  },
+	{ "e32k", RTC_EXT_CTRL_4B, RTC_CTRL_4B_E32K },
+	{ "cs",   RTC_EXT_CTRL_4B, RTC_CTRL_4B_CS   },
+	{ "rce",  RTC_EXT_CTRL_4B, RTC_CTRL_4B_RCE  },
+	{ "prs",  RTC_EXT_CTRL_4B, RTC_CTRL_4B_PRS  },
+	{ "rie",  RTC_EXT_CTRL_4B, RTC_CTRL_4B_RIE  },
+	{ "wie",  RTC_EXT_CTRL_4B, RTC_CTRL_4B_WIE  },
+	{ "kse",  RTC_EXT_CTRL_4B, RTC_CTRL_4B_KSE  },
+	{ NULL,   0,               0                },
+};
+
+/**
+ * ds1685_rtc_sysfs_ctrl_regs_lookup - ctrl register bit lookup function.
+ * @name: ctrl register bit to look up in ds1685_ctrl_regs_table.
+ */
+static const struct ds1685_rtc_ctrl_regs*
+ds1685_rtc_sysfs_ctrl_regs_lookup(const char *name)
+{
+	const struct ds1685_rtc_ctrl_regs *p = ds1685_ctrl_regs_table;
+
+	for (; p->name != NULL; ++p)
+		if (strcmp(p->name, name) == 0)
+			return p;
+
+	return NULL;
+}
+
+/**
+ * ds1685_rtc_sysfs_ctrl_regs_show - reads a ctrl register bit via sysfs.
+ * @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_ctrl_regs_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	u8 tmp;
+	struct ds1685_priv *rtc = dev_get_drvdata(dev);
+	const struct ds1685_rtc_ctrl_regs *reg_info =
+		ds1685_rtc_sysfs_ctrl_regs_lookup(attr->attr.name);
+
+	/* Make sure we actually matched something. */
+	if (!reg_info)
+		return -EINVAL;
+
+	/* No spinlock during a read -- mutex is already held. */
+	ds1685_rtc_switch_to_bank1(rtc);
+	tmp = rtc->read(rtc, reg_info->reg) & reg_info->bit;
+	ds1685_rtc_switch_to_bank0(rtc);
+
+	return snprintf(buf, 2, "%d\n", (tmp ? 1 : 0));
+}
+
+/**
+ * ds1685_rtc_sysfs_ctrl_regs_store - writes a ctrl register bit via sysfs.
+ * @dev: pointer to device structure.
+ * @attr: pointer to device_attribute structure.
+ * @buf: pointer to char array to hold the output.
+ * @count: number of bytes written.
+ */
+static ssize_t
+ds1685_rtc_sysfs_ctrl_regs_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	struct ds1685_priv *rtc = dev_get_drvdata(dev);
+	u8 reg = 0, bit = 0, tmp;
+	unsigned long flags = 0;
+	long int val = 0;
+	const struct ds1685_rtc_ctrl_regs *reg_info =
+		ds1685_rtc_sysfs_ctrl_regs_lookup(attr->attr.name);
+
+	/* We only accept numbers. */
+	if (kstrtol(buf, 10, &val) < 0)
+		return -EINVAL;
+
+	/* bits are binary, 0 or 1 only. */
+	if ((val != 0) && (val != 1))
+		return -ERANGE;
+
+	/* Make sure we actually matched something. */
+	if (!reg_info)
+		return -EINVAL;
+
+	reg = reg_info->reg;
+	bit = reg_info->bit;
+
+	/* Safe to spinlock during a write. */
+	ds1685_rtc_begin_ctrl_access(rtc, flags);
+	tmp = rtc->read(rtc, reg);
+	rtc->write(rtc, reg, (val ? (tmp | bit) : (tmp & ~(bit))));
+	ds1685_rtc_end_ctrl_access(rtc, flags);
+
+	return count;
+}
+
+/**
+ * DS1685_RTC_SYSFS_CTRL_REG_RO - device_attribute for read-only register bit.
+ * @bit: bit to read.
+ */
+#define DS1685_RTC_SYSFS_CTRL_REG_RO(bit)				\
+	static DEVICE_ATTR(bit, S_IRUGO,				\
+	ds1685_rtc_sysfs_ctrl_regs_show, NULL)
+
+/**
+ * DS1685_RTC_SYSFS_CTRL_REG_RW - device_attribute for read-write register bit.
+ * @bit: bit to read or write.
+ */
+#define DS1685_RTC_SYSFS_CTRL_REG_RW(bit)				\
+	static DEVICE_ATTR(bit, S_IRUGO | S_IWUSR,			\
+	ds1685_rtc_sysfs_ctrl_regs_show,				\
+	ds1685_rtc_sysfs_ctrl_regs_store)
+
+/*
+ * Control Register A bits.
+ */
+DS1685_RTC_SYSFS_CTRL_REG_RO(uip);
+DS1685_RTC_SYSFS_CTRL_REG_RW(dv2);
+DS1685_RTC_SYSFS_CTRL_REG_RW(dv1);
+DS1685_RTC_SYSFS_CTRL_REG_RO(dv0);
+DS1685_RTC_SYSFS_CTRL_REG_RW(rs3);
+DS1685_RTC_SYSFS_CTRL_REG_RW(rs2);
+DS1685_RTC_SYSFS_CTRL_REG_RW(rs1);
+DS1685_RTC_SYSFS_CTRL_REG_RW(rs0);
+
+static struct attribute*
+ds1685_rtc_sysfs_ctrla_attrs[] = {
+	&dev_attr_uip.attr,
+	&dev_attr_dv2.attr,
+	&dev_attr_dv1.attr,
+	&dev_attr_dv0.attr,
+	&dev_attr_rs3.attr,
+	&dev_attr_rs2.attr,
+	&dev_attr_rs1.attr,
+	&dev_attr_rs0.attr,
+	NULL,
+};
+
+static const struct attribute_group
+ds1685_rtc_sysfs_ctrla_grp = {
+	.name = "ctrla",
+	.attrs = ds1685_rtc_sysfs_ctrla_attrs,
+};
+
+
+/*
+ * Control Register B bits.
+ */
+DS1685_RTC_SYSFS_CTRL_REG_RO(set);
+DS1685_RTC_SYSFS_CTRL_REG_RW(pie);
+DS1685_RTC_SYSFS_CTRL_REG_RW(aie);
+DS1685_RTC_SYSFS_CTRL_REG_RW(uie);
+DS1685_RTC_SYSFS_CTRL_REG_RW(sqwe);
+DS1685_RTC_SYSFS_CTRL_REG_RO(dm);
+DS1685_RTC_SYSFS_CTRL_REG_RO(2412);
+DS1685_RTC_SYSFS_CTRL_REG_RO(dse);
+
+static struct attribute*
+ds1685_rtc_sysfs_ctrlb_attrs[] = {
+	&dev_attr_set.attr,
+	&dev_attr_pie.attr,
+	&dev_attr_aie.attr,
+	&dev_attr_uie.attr,
+	&dev_attr_sqwe.attr,
+	&dev_attr_dm.attr,
+	&dev_attr_2412.attr,
+	&dev_attr_dse.attr,
+	NULL,
+};
+
+static const struct attribute_group
+ds1685_rtc_sysfs_ctrlb_grp = {
+	.name = "ctrlb",
+	.attrs = ds1685_rtc_sysfs_ctrlb_attrs,
+};
+
+/*
+ * Control Register C bits.
+ *
+ * Reading Control C clears these bits!  Reading them individually can
+ * possibly cause an interrupt to be missed.  Use the /proc interface
+ * to see all the bits in this register simultaneously.
+ */
+DS1685_RTC_SYSFS_CTRL_REG_RO(irqf);
+DS1685_RTC_SYSFS_CTRL_REG_RO(pf);
+DS1685_RTC_SYSFS_CTRL_REG_RO(af);
+DS1685_RTC_SYSFS_CTRL_REG_RO(uf);
+
+static struct attribute*
+ds1685_rtc_sysfs_ctrlc_attrs[] = {
+	&dev_attr_irqf.attr,
+	&dev_attr_pf.attr,
+	&dev_attr_af.attr,
+	&dev_attr_uf.attr,
+	NULL,
+};
+
+static const struct attribute_group
+ds1685_rtc_sysfs_ctrlc_grp = {
+	.name = "ctrlc",
+	.attrs = ds1685_rtc_sysfs_ctrlc_attrs,
+};
+
+/*
+ * Control Register D bits.
+ */
+DS1685_RTC_SYSFS_CTRL_REG_RO(vrt);
+
+static struct attribute*
+ds1685_rtc_sysfs_ctrld_attrs[] = {
+	&dev_attr_vrt.attr,
+	NULL,
+};
+
+static const struct attribute_group
+ds1685_rtc_sysfs_ctrld_grp = {
+	.name = "ctrld",
+	.attrs = ds1685_rtc_sysfs_ctrld_attrs,
+};
+
+/*
+ * Control Register 4A bits.
+ */
+DS1685_RTC_SYSFS_CTRL_REG_RO(vrt2);
+DS1685_RTC_SYSFS_CTRL_REG_RO(incr);
+DS1685_RTC_SYSFS_CTRL_REG_RW(pab);
+DS1685_RTC_SYSFS_CTRL_REG_RW(rf);
+DS1685_RTC_SYSFS_CTRL_REG_RW(wf);
+DS1685_RTC_SYSFS_CTRL_REG_RW(kf);
+#if !defined(CONFIG_RTC_DRV_DS1685) && !defined(CONFIG_RTC_DRV_DS1689)
+DS1685_RTC_SYSFS_CTRL_REG_RO(bme);
+#endif
+
+static struct attribute*
+ds1685_rtc_sysfs_ctrl4a_attrs[] = {
+	&dev_attr_vrt2.attr,
+	&dev_attr_incr.attr,
+	&dev_attr_pab.attr,
+	&dev_attr_rf.attr,
+	&dev_attr_wf.attr,
+	&dev_attr_kf.attr,
+#if !defined(CONFIG_RTC_DRV_DS1685) && !defined(CONFIG_RTC_DRV_DS1689)
+	&dev_attr_bme.attr,
+#endif
+	NULL,
+};
+
+static const struct attribute_group
+ds1685_rtc_sysfs_ctrl4a_grp = {
+	.name = "ctrl4a",
+	.attrs = ds1685_rtc_sysfs_ctrl4a_attrs,
+};
+
+/*
+ * Control Register 4B bits.
+ */
+DS1685_RTC_SYSFS_CTRL_REG_RW(abe);
+DS1685_RTC_SYSFS_CTRL_REG_RW(e32k);
+DS1685_RTC_SYSFS_CTRL_REG_RO(cs);
+DS1685_RTC_SYSFS_CTRL_REG_RW(rce);
+DS1685_RTC_SYSFS_CTRL_REG_RW(prs);
+DS1685_RTC_SYSFS_CTRL_REG_RW(rie);
+DS1685_RTC_SYSFS_CTRL_REG_RW(wie);
+DS1685_RTC_SYSFS_CTRL_REG_RW(kse);
+
+static struct attribute*
+ds1685_rtc_sysfs_ctrl4b_attrs[] = {
+	&dev_attr_abe.attr,
+	&dev_attr_e32k.attr,
+	&dev_attr_cs.attr,
+	&dev_attr_rce.attr,
+	&dev_attr_prs.attr,
+	&dev_attr_rie.attr,
+	&dev_attr_wie.attr,
+	&dev_attr_kse.attr,
+	NULL,
+};
+
+static const struct attribute_group
+ds1685_rtc_sysfs_ctrl4b_grp = {
+	.name = "ctrl4b",
+	.attrs = ds1685_rtc_sysfs_ctrl4b_attrs,
+};
+
+
+/**
+ * struct ds1685_rtc_ctrl_regs.
+ * @name: char pointer for the bit name.
+ * @reg: control register the bit is in.
+ * @bit: the bit's offset in the register.
+ */
+struct ds1685_rtc_time_regs {
+	const char *name;
+	const u8 reg;
+	const u8 mask;
+	const u8 min;
+	const u8 max;
+};
+
+/*
+ * Time/Date register lookup tables.
+ */
+static const struct ds1685_rtc_time_regs
+ds1685_time_regs_bcd_table[] = {
+	{ "seconds",       RTC_SECS,       RTC_SECS_BCD_MASK,   0, 59 },
+	{ "minutes",       RTC_MINS,       RTC_MINS_BCD_MASK,   0, 59 },
+	{ "hours",         RTC_HRS,        RTC_HRS_24_BCD_MASK, 0, 23 },
+	{ "wday",          RTC_WDAY,       RTC_WDAY_MASK,       1,  7 },
+	{ "mday",          RTC_MDAY,       RTC_MDAY_BCD_MASK,   1, 31 },
+	{ "month",         RTC_MONTH,      RTC_MONTH_BCD_MASK,  1, 12 },
+	{ "year",          RTC_YEAR,       RTC_YEAR_BCD_MASK,   0, 99 },
+	{ "century",       RTC_CENTURY,    RTC_CENTURY_MASK,    0, 99 },
+	{ "alarm_seconds", RTC_SECS_ALARM, RTC_SECS_BCD_MASK,   0, 59 },
+	{ "alarm_minutes", RTC_MINS_ALARM, RTC_MINS_BCD_MASK,   0, 59 },
+	{ "alarm_hours",   RTC_HRS_ALARM,  RTC_HRS_24_BCD_MASK, 0, 23 },
+	{ "alarm_mday",    RTC_MDAY_ALARM, RTC_MDAY_ALARM_MASK, 1, 31 },
+	{ NULL,            0,              0,                   0,  0 },
+};
+
+static const struct ds1685_rtc_time_regs
+ds1685_time_regs_bin_table[] = {
+	{ "seconds",       RTC_SECS,       RTC_SECS_BIN_MASK,   0x00, 0x3b },
+	{ "minutes",       RTC_MINS,       RTC_MINS_BIN_MASK,   0x00, 0x3b },
+	{ "hours",         RTC_HRS,        RTC_HRS_24_BIN_MASK, 0x00, 0x17 },
+	{ "wday",          RTC_WDAY,       RTC_WDAY_MASK,       0x01, 0x07 },
+	{ "mday",          RTC_MDAY,       RTC_MDAY_BIN_MASK,   0x01, 0x1f },
+	{ "month",         RTC_MONTH,      RTC_MONTH_BIN_MASK,  0x01, 0x0c },
+	{ "year",          RTC_YEAR,       RTC_YEAR_BIN_MASK,   0x00, 0x63 },
+	{ "century",       RTC_CENTURY,    RTC_CENTURY_MASK,    0x00, 0x63 },
+	{ "alarm_seconds", RTC_SECS_ALARM, RTC_SECS_BIN_MASK,   0x00, 0x3b },
+	{ "alarm_minutes", RTC_MINS_ALARM, RTC_MINS_BIN_MASK,   0x00, 0x3b },
+	{ "alarm_hours",   RTC_HRS_ALARM,  RTC_HRS_24_BIN_MASK, 0x00, 0x17 },
+	{ "alarm_mday",    RTC_MDAY_ALARM, RTC_MDAY_ALARM_MASK, 0x01, 0x1f },
+	{ NULL,            0,              0,                   0x00, 0x00 },
+};
+
+/**
+ * ds1685_rtc_sysfs_time_regs_bcd_lookup - time/date reg bit lookup function.
+ * @name: register bit to look up in ds1685_time_regs_bcd_table.
+ */
+static const struct ds1685_rtc_time_regs*
+ds1685_rtc_sysfs_time_regs_lookup(const char *name, bool bcd_mode)
+{
+	const struct ds1685_rtc_time_regs *p;
+
+	if (bcd_mode)
+		p = ds1685_time_regs_bcd_table;
+	else
+		p = ds1685_time_regs_bin_table;
+
+	for (; p->name != NULL; ++p)
+		if (strcmp(p->name, name) == 0)
+			return p;
+
+	return NULL;
+}
+
+/**
+ * ds1685_rtc_sysfs_time_regs_show - reads a time/date register via sysfs.
+ * @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_time_regs_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	u8 tmp;
+	struct ds1685_priv *rtc = dev_get_drvdata(dev);
+	const struct ds1685_rtc_time_regs *bcd_reg_info =
+		ds1685_rtc_sysfs_time_regs_lookup(attr->attr.name, true);
+	const struct ds1685_rtc_time_regs *bin_reg_info =
+		ds1685_rtc_sysfs_time_regs_lookup(attr->attr.name, false);
+
+	/* Make sure we actually matched something. */
+	if (!bcd_reg_info && !bin_reg_info)
+		return -EINVAL;
+
+	/* bcd_reg_info->reg == bin_reg_info->reg. */
+	ds1685_rtc_begin_data_access(rtc);
+	tmp = rtc->read(rtc, bcd_reg_info->reg);
+	ds1685_rtc_end_data_access(rtc);
+
+	tmp = ds1685_rtc_bcd2bin(rtc, tmp, bcd_reg_info->mask,
+				 bin_reg_info->mask);
+
+	return snprintf(buf, 4, "%d\n", tmp);
+}
+
+/**
+ * ds1685_rtc_sysfs_time_regs_store - writes a time/date register via sysfs.
+ * @dev: pointer to device structure.
+ * @attr: pointer to device_attribute structure.
+ * @buf: pointer to char array to hold the output.
+ * @count: number of bytes written.
+ */
+static ssize_t
+ds1685_rtc_sysfs_time_regs_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	long int val = 0;
+	struct ds1685_priv *rtc = dev_get_drvdata(dev);
+	const struct ds1685_rtc_time_regs *bcd_reg_info =
+		ds1685_rtc_sysfs_time_regs_lookup(attr->attr.name, true);
+	const struct ds1685_rtc_time_regs *bin_reg_info =
+		ds1685_rtc_sysfs_time_regs_lookup(attr->attr.name, false);
+
+	/* We only accept numbers. */
+	if (kstrtol(buf, 10, &val) < 0)
+		return -EINVAL;
+
+	/* Make sure we actually matched something. */
+	if (!bcd_reg_info && !bin_reg_info)
+		return -EINVAL;
+
+	/* Check for a valid range. */
+	if (rtc->bcd_mode) {
+		if ((val < bcd_reg_info->min) || (val > bcd_reg_info->max))
+			return -ERANGE;
+	} else {
+		if ((val < bin_reg_info->min) || (val > bin_reg_info->max))
+			return -ERANGE;
+	}
+
+	val = ds1685_rtc_bin2bcd(rtc, val, bin_reg_info->mask,
+				 bcd_reg_info->mask);
+
+	/* bcd_reg_info->reg == bin_reg_info->reg. */
+	ds1685_rtc_begin_data_access(rtc);
+	rtc->write(rtc, bcd_reg_info->reg, val);
+	ds1685_rtc_end_data_access(rtc);
+
+	return count;
+}
+
+/**
+ * DS1685_RTC_SYSFS_REG_RW - device_attribute for a read-write time register.
+ * @reg: time/date register to read or write.
+ */
+#define DS1685_RTC_SYSFS_TIME_REG_RW(reg)				\
+	static DEVICE_ATTR(reg, S_IRUGO | S_IWUSR,			\
+	ds1685_rtc_sysfs_time_regs_show,				\
+	ds1685_rtc_sysfs_time_regs_store)
+
+/*
+ * Time/Date Register bits.
+ */
+DS1685_RTC_SYSFS_TIME_REG_RW(seconds);
+DS1685_RTC_SYSFS_TIME_REG_RW(minutes);
+DS1685_RTC_SYSFS_TIME_REG_RW(hours);
+DS1685_RTC_SYSFS_TIME_REG_RW(wday);
+DS1685_RTC_SYSFS_TIME_REG_RW(mday);
+DS1685_RTC_SYSFS_TIME_REG_RW(month);
+DS1685_RTC_SYSFS_TIME_REG_RW(year);
+DS1685_RTC_SYSFS_TIME_REG_RW(century);
+DS1685_RTC_SYSFS_TIME_REG_RW(alarm_seconds);
+DS1685_RTC_SYSFS_TIME_REG_RW(alarm_minutes);
+DS1685_RTC_SYSFS_TIME_REG_RW(alarm_hours);
+DS1685_RTC_SYSFS_TIME_REG_RW(alarm_mday);
+
+static struct attribute*
+ds1685_rtc_sysfs_time_attrs[] = {
+	&dev_attr_seconds.attr,
+	&dev_attr_minutes.attr,
+	&dev_attr_hours.attr,
+	&dev_attr_wday.attr,
+	&dev_attr_mday.attr,
+	&dev_attr_month.attr,
+	&dev_attr_year.attr,
+	&dev_attr_century.attr,
+	NULL,
+};
+
+static const struct attribute_group
+ds1685_rtc_sysfs_time_grp = {
+	.name = "datetime",
+	.attrs = ds1685_rtc_sysfs_time_attrs,
+};
+
+static struct attribute*
+ds1685_rtc_sysfs_alarm_attrs[] = {
+	&dev_attr_alarm_seconds.attr,
+	&dev_attr_alarm_minutes.attr,
+	&dev_attr_alarm_hours.attr,
+	&dev_attr_alarm_mday.attr,
+	NULL,
+};
+
+static const struct attribute_group
+ds1685_rtc_sysfs_alarm_grp = {
+	.name = "alarm",
+	.attrs = ds1685_rtc_sysfs_alarm_attrs,
+};
+#endif /* CONFIG_RTC_DS1685_SYSFS_REGS */
+
+
+/**
+ * ds1685_rtc_sysfs_register - register sysfs files.
+ * @dev: pointer to device structure.
+ */
+static int
+ds1685_rtc_sysfs_register(struct device *dev)
+{
+	int ret = 0;
+
+	sysfs_bin_attr_init(&ds1685_rtc_sysfs_nvram_attr);
+	ret = sysfs_create_bin_file(&dev->kobj, &ds1685_rtc_sysfs_nvram_attr);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_misc_grp);
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_RTC_DS1685_SYSFS_REGS
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_ctrla_grp);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_ctrlb_grp);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_ctrlc_grp);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_ctrld_grp);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_ctrl4a_grp);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_ctrl4b_grp);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_time_grp);
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_group(&dev->kobj, &ds1685_rtc_sysfs_alarm_grp);
+	if (ret)
+		return ret;
+#endif
+	return 0;
+}
+
+/**
+ * ds1685_rtc_sysfs_unregister - unregister sysfs files.
+ * @dev: pointer to device structure.
+ */
+static int
+ds1685_rtc_sysfs_unregister(struct device *dev)
+{
+	sysfs_remove_bin_file(&dev->kobj, &ds1685_rtc_sysfs_nvram_attr);
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_misc_grp);
+
+#ifdef CONFIG_RTC_DS1685_SYSFS_REGS
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_ctrla_grp);
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_ctrlb_grp);
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_ctrlc_grp);
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_ctrld_grp);
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_ctrl4a_grp);
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_ctrl4b_grp);
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_time_grp);
+	sysfs_remove_group(&dev->kobj, &ds1685_rtc_sysfs_alarm_grp);
+#endif
+
+	return 0;
+}
+#endif /* CONFIG_SYSFS */
+
+
+
+/* ----------------------------------------------------------------------- */
+/* 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 resource *res;
+	struct ds1685_priv *rtc;
+	struct ds1685_rtc_platform_data *pdata;
+	u8 ctrla, ctrlb, hours;
+	unsigned char am_pm;
+	int ret = 0;
+
+	/* 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;
+
+	/*
+	 * Allocate/setup any IORESOURCE_MEM resources, if required.  Not all
+	 * platforms put the RTC in an easy-access place.  Like the SGI Octane,
+	 * which attaches the RTC to a "ByteBus", hooked to a SuperIO chip
+	 * that sits behind the IOC3 PCI metadevice.
+	 */
+	if (pdata->alloc_io_resources) {
+		/* Get the platform resources. */
+		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		if (!res)
+			return -ENXIO;
+		rtc->size = resource_size(res);
+
+		/* Request a memory region. */
+		/* XXX: mmio-only for now. */
+		if (!devm_request_mem_region(&pdev->dev, res->start, rtc->size,
+					     pdev->name))
+			return -EBUSY;
+
+		/*
+		 * Set the base address for the rtc, and ioremap its
+		 * registers.
+		 */
+		rtc->baseaddr = res->start;
+		rtc->regs = devm_ioremap(&pdev->dev, res->start, rtc->size);
+		if (!rtc->regs)
+			return -ENOMEM;
+	}
+	rtc->alloc_io_resources = pdata->alloc_io_resources;
+
+	/* Get the register step size. */
+	if (pdata->regstep > 0)
+		rtc->regstep = pdata->regstep;
+	else
+		rtc->regstep = 1;
+
+	/* Platform read function, else default if mmio setup */
+	if (pdata->plat_read)
+		rtc->read = pdata->plat_read;
+	else
+		if (pdata->alloc_io_resources)
+			rtc->read = ds1685_read;
+		else
+			return -ENXIO;
+
+	/* Platform write function, else default if mmio setup */
+	if (pdata->plat_write)
+		rtc->write = pdata->plat_write;
+	else
+		if (pdata->alloc_io_resources)
+			rtc->write = ds1685_write;
+		else
+			return -ENXIO;
+
+	/* 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;
+
+	/* Init the spinlock, workqueue, & set the driver data. */
+	spin_lock_init(&rtc->lock);
+	INIT_WORK(&rtc->work, ds1685_rtc_work_queue);
+	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!\n");
+
+	/* 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.\n");
+
+	/* 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));
+
+	/*
+	 * 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) {
+			rtc->irq_num = ret;
+
+			/* Request an IRQ. */
+			ret = devm_request_irq(&pdev->dev, rtc->irq_num,
+					       ds1685_rtc_irq_handler,
+					       IRQF_SHARED, pdev->name, pdev);
+
+			/* Check to see if something came back. */
+			if (unlikely(ret)) {
+				dev_warn(&pdev->dev,
+					 "RTC interrupt not available\n");
+				rtc->irq_num = 0;
+			}
+		} else
+			return ret;
+	}
+	rtc->no_irq = pdata->no_irq;
+
+	/* Setup complete. */
+	ds1685_rtc_switch_to_bank0(rtc);
+
+	/* Register the device as an RTC. */
+	rtc_dev = rtc_device_register(pdev->name, &pdev->dev,
+				      &ds1685_rtc_ops, THIS_MODULE);
+
+	/* Success? */
+	if (IS_ERR(rtc_dev))
+		return PTR_ERR(rtc_dev);
+
+	/* 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->uie_unsupported = pdata->uie_unsupported;
+
+	rtc->dev = rtc_dev;
+
+#ifdef CONFIG_SYSFS
+	ret = ds1685_rtc_sysfs_register(&pdev->dev);
+	if (ret)
+		rtc_device_unregister(rtc->dev);
+#endif
+
+	/* Done! */
+	return ret;
+}
+
+/**
+ * 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);
+
+#ifdef CONFIG_SYSFS
+	ds1685_rtc_sysfs_unregister(&pdev->dev);
+#endif
+
+	rtc_device_unregister(rtc->dev);
+
+	/* 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)));
+
+	cancel_work_sync(&rtc->work);
+
+	return 0;
+}
+
+/**
+ * ds1685_rtc_driver - rtc driver properties.
+ */
+static struct platform_driver ds1685_rtc_driver = {
+	.driver		= {
+		.name	= "rtc-ds1685",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= ds1685_rtc_probe,
+	.remove		= ds1685_rtc_remove,
+};
+
+/**
+ * ds1685_rtc_init - rtc module init.
+ */
+static int __init
+ds1685_rtc_init(void)
+{
+	return platform_driver_register(&ds1685_rtc_driver);
+}
+
+/**
+ * ds1685_rtc_exit - rtc module exit.
+ */
+static void __exit
+ds1685_rtc_exit(void)
+{
+	platform_driver_unregister(&ds1685_rtc_driver);
+}
+
+module_init(ds1685_rtc_init);
+module_exit(ds1685_rtc_exit);
+/* ----------------------------------------------------------------------- */
+
+
+/* ----------------------------------------------------------------------- */
+/* Poweroff function */
+
+/**
+ * ds1685_rtc_poweroff - uses the RTC chip to power the system off.
+ * @pdev: pointer to platform_device structure.
+ */
+extern 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("rtc-ds1685: platform device data not available, spinning forever ...\n");
+		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.\n");
+		msleep(20);
+		rtc->write(rtc, RTC_EXT_CTRL_4A,
+			   (ctrl4a | RTC_CTRL_4A_PAB));
+
+		/* Spin ... we do not switch back to bank0. */
+		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_VERSION(DRV_VERSION);
+MODULE_ALIAS("platform:rtc-ds1685");