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>

3 files changed, 2343 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 3bc9ddbe5cf7..0cf2e1d9cb17 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -801,6 +801,96 @@ config RTC_DRV_DS1553
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-ds1553.
 
+config RTC_DRV_DS1685_FAMILY
+	tristate "Dallas/Maxim DS1685 Family"
+	help
+	  If you say yes here you get support for the Dallas/Maxim DS1685
+	  family of real time chips.  This family includes the DS1685/DS1687,
+	  DS1689/DS1693, DS17285/DS17287, DS17485/DS17487, and
+	  DS17885/DS17887 chips.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-ds1685.
+
+choice
+	prompt "Subtype"
+	depends on RTC_DRV_DS1685_FAMILY
+	default RTC_DRV_DS1685
+
+config RTC_DRV_DS1685
+	bool "DS1685/DS1687"
+	help
+	  This enables support for the Dallas/Maxim DS1685/DS1687 real time
+	  clock chip.
+
+	  This chip is commonly found in SGI O2 (IP32) and SGI Octane (IP30)
+	  systems, as well as EPPC-405-UC modules by electronic system design
+	  GmbH.
+
+config RTC_DRV_DS1689
+	bool "DS1689/DS1693"
+	help
+	  This enables support for the Dallas/Maxim DS1689/DS1693 real time
+	  clock chip.
+
+	  This is an older RTC chip, supplanted by the DS1685/DS1687 above,
+	  which supports a few minor features such as Vcc, Vbat, and Power
+	  Cycle counters, plus a customer-specific, 8-byte ROM/Serial number.
+
+	  It also works for the even older DS1688/DS1691 RTC chips, which are
+	  virtually the same and carry the same model number.  Both chips
+	  have 114 bytes of user NVRAM.
+
+config RTC_DRV_DS17285
+	bool "DS17285/DS17287"
+	help
+	  This enables support for the Dallas/Maxim DS17285/DS17287 real time
+	  clock chip.
+
+	  This chip features 2kb of extended NV-SRAM.  It may possibly be
+	  found in some SGI O2 systems (rare).
+
+config RTC_DRV_DS17485
+	bool "DS17485/DS17487"
+	help
+	  This enables support for the Dallas/Maxim DS17485/DS17487 real time
+	  clock chip.
+
+	  This chip features 4kb of extended NV-SRAM.
+
+config RTC_DRV_DS17885
+	bool "DS17885/DS17887"
+	help
+	  This enables support for the Dallas/Maxim DS17885/DS17887 real time
+	  clock chip.
+
+	  This chip features 8kb of extended NV-SRAM.
+
+endchoice
+
+config RTC_DS1685_PROC_REGS
+	bool "Display register values in /proc"
+	depends on RTC_DRV_DS1685_FAMILY && PROC_FS
+	help
+	  Enable this to display a readout of all of the RTC registers in
+	  /proc/drivers/rtc.  Keep in mind that this can potentially lead
+	  to lost interrupts, as reading Control Register C will clear
+	  all pending IRQ flags.
+
+	  Unless you are debugging this driver, choose N.
+
+config RTC_DS1685_SYSFS_REGS
+	bool "SysFS access to RTC register bits"
+	depends on RTC_DRV_DS1685_FAMILY && SYSFS
+	help
+	  Enable this to provide access to the RTC control register bits
+	  in /sys.  Some of the bits are read-write, others are read-only.
+
+	  Keep in mind that reading Control C's bits automatically clears
+	  all pending IRQ flags - this can cause lost interrupts.
+
+	  If you know that you need access to these bits, choose Y, Else N.
+
 config RTC_DRV_DS1742
 	tristate "Maxim/Dallas DS1742/1743"
 	depends on HAS_IOMEM
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 99ded8b75e95..69c87062b098 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_RTC_DRV_DS1390)	+= rtc-ds1390.o
 obj-$(CONFIG_RTC_DRV_DS1511)	+= rtc-ds1511.o
 obj-$(CONFIG_RTC_DRV_DS1553)	+= rtc-ds1553.o
 obj-$(CONFIG_RTC_DRV_DS1672)	+= rtc-ds1672.o
+obj-$(CONFIG_RTC_DRV_DS1685_FAMILY)	+= rtc-ds1685.o
 obj-$(CONFIG_RTC_DRV_DS1742)	+= rtc-ds1742.o
 obj-$(CONFIG_RTC_DRV_DS2404)    += rtc-ds2404.o
 obj-$(CONFIG_RTC_DRV_DS3232)	+= rtc-ds3232.o
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,
+};
+/* ----------------------------------------------------------------------- */