Linux 6.13-rc4

[linux.git] / drivers / rtc / rtc-ds1685.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * An rtc driver for the Dallas/Maxim DS1685/DS1687 and related real-time
 * chips.
 *
 * Copyright (C) 2011-2014 Joshua Kinard <kumba@gentoo.org>.
 * Copyright (C) 2009 Matthias Fuchs <matthias.fuchs@esd-electronics.com>.
 *
 * References:
 *    DS1685/DS1687 3V/5V Real-Time Clocks, 19-5215, Rev 4/10.
 *    DS17x85/DS17x87 3V/5V Real-Time Clocks, 19-5222, Rev 4/10.
 *    DS1689/DS1693 3V/5V Serialized Real-Time Clocks, Rev 112105.
 *    Application Note 90, Using the Multiplex Bus RTC Extended Features.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bcd.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/workqueue.h>

#include <linux/rtc/ds1685.h>

#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
#endif


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

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

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

/*
 * Indirect read/write functions
 * access happens via address and data register mapped in CPU address space
 */

/**
 * ds1685_indirect_read - read a value from an rtc register.
 * @rtc: pointer to the ds1685 rtc structure.
 * @reg: the register address to read.
 */
static u8
ds1685_indirect_read(struct ds1685_priv *rtc, int reg)
{
        writeb(reg, rtc->regs);
        return readb(rtc->data);
}

/**
 * ds1685_indirect_write - write a value to an rtc register.
 * @rtc: pointer to the ds1685 rtc structure.
 * @reg: the register address to write.
 * @value: value to write to the register.
 */
static void
ds1685_indirect_write(struct ds1685_priv *rtc, int reg, u8 value)
{
        writeb(reg, rtc->regs);
        writeb(value, rtc->data);
}

/* ----------------------------------------------------------------------- */
/* Inlined functions */

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

        return (val & bin_mask);
}

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

        return (val & bin_mask);
}

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

/**
 * ds1685_rtc_switch_to_bank0 - switch the rtc to bank 0.
 * @rtc: pointer to the ds1685 rtc structure.
 */
static inline void
ds1685_rtc_switch_to_bank0(struct ds1685_priv *rtc)
{
        rtc->write(rtc, RTC_CTRL_A,
                   (rtc->read(rtc, RTC_CTRL_A) & ~(RTC_CTRL_A_DV0)));
}

/**
 * ds1685_rtc_switch_to_bank1 - switch the rtc to bank 1.
 * @rtc: pointer to the ds1685 rtc structure.
 */
static inline void
ds1685_rtc_switch_to_bank1(struct ds1685_priv *rtc)
{
        rtc->write(rtc, RTC_CTRL_A,
                   (rtc->read(rtc, RTC_CTRL_A) | RTC_CTRL_A_DV0));
}

/**
 * ds1685_rtc_begin_data_access - prepare the rtc for data access.
 * @rtc: pointer to the ds1685 rtc structure.
 *
 * This takes several steps to prepare the rtc for access to get/set time
 * and alarm values from the rtc registers:
 *  - Sets the SET bit in Control Register B.
 *  - Reads Ext Control Register 4A and checks the INCR bit.
 *  - If INCR is active, a short delay is added before Ext Control Register 4A
 *    is read again in a loop until INCR is inactive.
 *  - Switches the rtc to bank 1.  This allows access to all relevant
 *    data for normal rtc operation, as bank 0 contains only the nvram.
 */
static inline void
ds1685_rtc_begin_data_access(struct ds1685_priv *rtc)
{
        /* Set the SET bit in Ctrl B */
        rtc->write(rtc, RTC_CTRL_B,
                   (rtc->read(rtc, RTC_CTRL_B) | RTC_CTRL_B_SET));

        /* Switch to Bank 1 */
        ds1685_rtc_switch_to_bank1(rtc);

        /* 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();
}

/**
 * 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_bank0(rtc);

        /* Clear the SET bit in Ctrl B */
        rtc->write(rtc, RTC_CTRL_B,
                   (rtc->read(rtc, RTC_CTRL_B) & ~(RTC_CTRL_B_SET)));
}

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


/* ----------------------------------------------------------------------- */
/* Read/Set Time & Alarm functions */

/**
 * ds1685_rtc_read_time - reads the time registers.
 * @dev: pointer to device structure.
 * @tm: pointer to rtc_time structure.
 */
static int
ds1685_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct ds1685_priv *rtc = dev_get_drvdata(dev);
        u8 century;
        u8 seconds, minutes, hours, wday, mday, month, years;

        /* Fetch the time info from the RTC registers. */
        ds1685_rtc_begin_data_access(rtc);
        seconds = rtc->read(rtc, RTC_SECS);
        minutes = rtc->read(rtc, RTC_MINS);
        hours   = rtc->read(rtc, RTC_HRS);
        wday    = rtc->read(rtc, RTC_WDAY);
        mday    = rtc->read(rtc, RTC_MDAY);
        month   = rtc->read(rtc, RTC_MONTH);
        years   = rtc->read(rtc, RTC_YEAR);
        century = rtc->read(rtc, RTC_CENTURY);
        ds1685_rtc_end_data_access(rtc);

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

        return 0;
}

/**
 * ds1685_rtc_set_time - sets the time registers.
 * @dev: pointer to device structure.
 * @tm: pointer to rtc_time structure.
 */
static int
ds1685_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct ds1685_priv *rtc = dev_get_drvdata(dev);
        u8 ctrlb, seconds, minutes, hours, wday, mday, month, years, century;

        /* Fetch the time info from rtc_time. */
        seconds = ds1685_rtc_bin2bcd(rtc, tm->tm_sec, RTC_SECS_BIN_MASK,
                                     RTC_SECS_BCD_MASK);
        minutes = ds1685_rtc_bin2bcd(rtc, tm->tm_min, RTC_MINS_BIN_MASK,
                                     RTC_MINS_BCD_MASK);
        hours   = ds1685_rtc_bin2bcd(rtc, tm->tm_hour, RTC_HRS_24_BIN_MASK,
                                     RTC_HRS_24_BCD_MASK);
        wday    = ds1685_rtc_bin2bcd(rtc, (tm->tm_wday + 1), RTC_WDAY_MASK,
                                     RTC_WDAY_MASK);
        mday    = ds1685_rtc_bin2bcd(rtc, tm->tm_mday, RTC_MDAY_BIN_MASK,
                                     RTC_MDAY_BCD_MASK);
        month   = ds1685_rtc_bin2bcd(rtc, (tm->tm_mon + 1), RTC_MONTH_BIN_MASK,
                                     RTC_MONTH_BCD_MASK);
        years   = ds1685_rtc_bin2bcd(rtc, (tm->tm_year % 100),
                                     RTC_YEAR_BIN_MASK, RTC_YEAR_BCD_MASK);
        century = ds1685_rtc_bin2bcd(rtc, ((tm->tm_year + 1900) / 100),
                                     RTC_CENTURY_MASK, RTC_CENTURY_MASK);

        /*
         * Perform Sanity Checks:
         *   - Months: !> 12, Month Day != 0.
         *   - Month Day !> Max days in current month.
         *   - Hours !>= 24, Mins !>= 60, Secs !>= 60, & Weekday !> 7.
         */
        if ((tm->tm_mon > 11) || (mday == 0))
                return -EDOM;

        if (tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year))
                return -EDOM;

        if ((tm->tm_hour >= 24) || (tm->tm_min >= 60) ||
            (tm->tm_sec >= 60)  || (wday > 7))
                return -EDOM;

        /*
         * Set the data mode to use and store the time values in the
         * RTC registers.
         */
        ds1685_rtc_begin_data_access(rtc);
        ctrlb = rtc->read(rtc, RTC_CTRL_B);
        if (rtc->bcd_mode)
                ctrlb &= ~(RTC_CTRL_B_DM);
        else
                ctrlb |= RTC_CTRL_B_DM;
        rtc->write(rtc, RTC_CTRL_B, ctrlb);
        rtc->write(rtc, RTC_SECS, seconds);
        rtc->write(rtc, RTC_MINS, minutes);
        rtc->write(rtc, RTC_HRS, hours);
        rtc->write(rtc, RTC_WDAY, wday);
        rtc->write(rtc, RTC_MDAY, mday);
        rtc->write(rtc, RTC_MONTH, month);
        rtc->write(rtc, RTC_YEAR, years);
        rtc->write(rtc, RTC_CENTURY, century);
        ds1685_rtc_end_data_access(rtc);

        return 0;
}

/**
 * ds1685_rtc_read_alarm - reads the alarm registers.
 * @dev: pointer to device structure.
 * @alrm: pointer to rtc_wkalrm structure.
 *
 * There are three primary alarm registers: seconds, minutes, and hours.
 * A fourth alarm register for the month date is also available in bank1 for
 * kickstart/wakeup features.  The DS1685/DS1687 manual states that a
 * "don't care" value ranging from 0xc0 to 0xff may be written into one or
 * more of the three alarm bytes to act as a wildcard value.  The fourth
 * byte doesn't support a "don't care" value.
 */
static int
ds1685_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct ds1685_priv *rtc = dev_get_drvdata(dev);
        u8 seconds, minutes, hours, mday, ctrlb, ctrlc;
        int ret;

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

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

        /*
         * Check the three alarm bytes.
         *
         * The Linux RTC system doesn't support the "don't care" capability
         * of this RTC chip.  We check for it anyways in case support is
         * added in the future and only assign when we care.
         */
        if (likely(seconds < 0xc0))
                alrm->time.tm_sec = ds1685_rtc_bcd2bin(rtc, seconds,
                                                       RTC_SECS_BCD_MASK,
                                                       RTC_SECS_BIN_MASK);

        if (likely(minutes < 0xc0))
                alrm->time.tm_min = ds1685_rtc_bcd2bin(rtc, minutes,
                                                       RTC_MINS_BCD_MASK,
                                                       RTC_MINS_BIN_MASK);

        if (likely(hours < 0xc0))
                alrm->time.tm_hour = ds1685_rtc_bcd2bin(rtc, hours,
                                                        RTC_HRS_24_BCD_MASK,
                                                        RTC_HRS_24_BIN_MASK);

        /* Write the data to rtc_wkalrm. */
        alrm->time.tm_mday = ds1685_rtc_bcd2bin(rtc, mday, RTC_MDAY_BCD_MASK,
                                                RTC_MDAY_BIN_MASK);
        alrm->enabled = !!(ctrlb & RTC_CTRL_B_AIE);
        alrm->pending = !!(ctrlc & RTC_CTRL_C_AF);

        return 0;
}

/**
 * ds1685_rtc_set_alarm - sets the alarm in registers.
 * @dev: pointer to device structure.
 * @alrm: pointer to rtc_wkalrm structure.
 */
static int
ds1685_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct ds1685_priv *rtc = dev_get_drvdata(dev);
        u8 ctrlb, seconds, minutes, hours, mday;
        int ret;

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

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

        /*
         * Check the three alarm bytes.
         *
         * The Linux RTC system doesn't support the "don't care" capability
         * of this RTC chip because rtc_valid_tm tries to validate every
         * field, and we only support four fields.  We put the support
         * here anyways for the future.
         */
        if (unlikely(seconds >= 0xc0))
                seconds = 0xff;

        if (unlikely(minutes >= 0xc0))
                minutes = 0xff;

        if (unlikely(hours >= 0xc0))
                hours = 0xff;

        alrm->time.tm_mon       = -1;
        alrm->time.tm_year      = -1;
        alrm->time.tm_wday      = -1;
        alrm->time.tm_yday      = -1;
        alrm->time.tm_isdst     = -1;

        /* Disable the alarm interrupt first. */
        ds1685_rtc_begin_data_access(rtc);
        ctrlb = rtc->read(rtc, RTC_CTRL_B);
        rtc->write(rtc, RTC_CTRL_B, (ctrlb & ~(RTC_CTRL_B_AIE)));

        /* Read ctrlc to clear RTC_CTRL_C_AF. */
        rtc->read(rtc, RTC_CTRL_C);

        /*
         * Set the data mode to use and store the time values in the
         * RTC registers.
         */
        ctrlb = rtc->read(rtc, RTC_CTRL_B);
        if (rtc->bcd_mode)
                ctrlb &= ~(RTC_CTRL_B_DM);
        else
                ctrlb |= RTC_CTRL_B_DM;
        rtc->write(rtc, RTC_CTRL_B, ctrlb);
        rtc->write(rtc, RTC_SECS_ALARM, seconds);
        rtc->write(rtc, RTC_MINS_ALARM, minutes);
        rtc->write(rtc, RTC_HRS_ALARM, hours);
        rtc->write(rtc, RTC_MDAY_ALARM, mday);

        /* Re-enable the alarm if needed. */
        if (alrm->enabled) {
                ctrlb = rtc->read(rtc, RTC_CTRL_B);
                ctrlb |= RTC_CTRL_B_AIE;
                rtc->write(rtc, RTC_CTRL_B, ctrlb);
        }

        /* Done! */
        ds1685_rtc_end_data_access(rtc);

        return 0;
}
/* ----------------------------------------------------------------------- */


/* ----------------------------------------------------------------------- */
/* /dev/rtcX Interface functions */

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

        /* Flip the requisite interrupt-enable bit. */
        if (enabled)
                rtc->write(rtc, RTC_CTRL_B, (rtc->read(rtc, RTC_CTRL_B) |
                                             RTC_CTRL_B_AIE));
        else
                rtc->write(rtc, RTC_CTRL_B, (rtc->read(rtc, RTC_CTRL_B) &
                                             ~(RTC_CTRL_B_AIE)));

        /* Read Control C to clear all the flag bits. */
        rtc->read(rtc, RTC_CTRL_C);

        return 0;
}
/* ----------------------------------------------------------------------- */


/* ----------------------------------------------------------------------- */
/* IRQ handler */

/**
 * ds1685_rtc_extended_irq - take care of extended interrupts
 * @rtc: pointer to the ds1685 rtc structure.
 * @pdev: platform device pointer.
 */
static void
ds1685_rtc_extended_irq(struct ds1685_priv *rtc, struct platform_device *pdev)
{
        u8 ctrl4a, ctrl4b;

        ds1685_rtc_switch_to_bank1(rtc);
        ctrl4a = rtc->read(rtc, RTC_EXT_CTRL_4A);
        ctrl4b = rtc->read(rtc, RTC_EXT_CTRL_4B);

        /*
         * Check for a kickstart interrupt. With Vcc applied, this
         * typically means that the power button was pressed, so we
         * begin the shutdown sequence.
         */
        if ((ctrl4b & RTC_CTRL_4B_KSE) && (ctrl4a & RTC_CTRL_4A_KF)) {
                /* Briefly disable kickstarts to debounce button presses. */
                rtc->write(rtc, RTC_EXT_CTRL_4B,
                           (rtc->read(rtc, RTC_EXT_CTRL_4B) &
                            ~(RTC_CTRL_4B_KSE)));

                /* Clear the kickstart flag. */
                rtc->write(rtc, RTC_EXT_CTRL_4A,
                           (ctrl4a & ~(RTC_CTRL_4A_KF)));


                /*
                 * Sleep 500ms before re-enabling kickstarts.  This allows
                 * adequate time to avoid reading signal jitter as additional
                 * button presses.
                 */
                msleep(500);
                rtc->write(rtc, RTC_EXT_CTRL_4B,
                           (rtc->read(rtc, RTC_EXT_CTRL_4B) |
                            RTC_CTRL_4B_KSE));

                /* Call the platform pre-poweroff function. Else, shutdown. */
                if (rtc->prepare_poweroff != NULL)
                        rtc->prepare_poweroff();
                else
                        ds1685_rtc_poweroff(pdev);
        }

        /*
         * Check for a wake-up interrupt.  With Vcc applied, this is
         * essentially a second alarm interrupt, except it takes into
         * account the 'date' register in bank1 in addition to the
         * standard three alarm registers.
         */
        if ((ctrl4b & RTC_CTRL_4B_WIE) && (ctrl4a & RTC_CTRL_4A_WF)) {
                rtc->write(rtc, RTC_EXT_CTRL_4A,
                           (ctrl4a & ~(RTC_CTRL_4A_WF)));

                /* Call the platform wake_alarm function if defined. */
                if (rtc->wake_alarm != NULL)
                        rtc->wake_alarm();
                else
                        dev_warn(&pdev->dev,
                                 "Wake Alarm IRQ just occurred!\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);
}

/**
 * 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;

        rtc_lock(rtc->dev);

        /* Ctrlb holds the interrupt-enable bits and ctrlc the flag bits. */
        ctrlb = rtc->read(rtc, RTC_CTRL_B);
        ctrlc = rtc->read(rtc, RTC_CTRL_C);

        /* Is the IRQF bit set? */
        if (likely(ctrlc & RTC_CTRL_C_IRQF)) {
                /*
                 * We need to determine if it was one of the standard
                 * events: PF, AF, or UF.  If so, we handle them and
                 * update the RTC core.
                 */
                if (likely(ctrlc & RTC_CTRL_B_PAU_MASK)) {
                        events = RTC_IRQF;

                        /* Check for a periodic interrupt. */
                        if ((ctrlb & RTC_CTRL_B_PIE) &&
                            (ctrlc & RTC_CTRL_C_PF)) {
                                events |= RTC_PF;
                                num_irqs++;
                        }

                        /* Check for an alarm interrupt. */
                        if ((ctrlb & RTC_CTRL_B_AIE) &&
                            (ctrlc & RTC_CTRL_C_AF)) {
                                events |= RTC_AF;
                                num_irqs++;
                        }

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

        return events ? IRQ_HANDLED : IRQ_NONE;
}
/* ----------------------------------------------------------------------- */


/* ----------------------------------------------------------------------- */
/* ProcFS interface */

#ifdef CONFIG_PROC_FS
#define NUM_REGS        6       /* Num of control registers. */
#define NUM_BITS        8       /* Num bits per register. */
#define NUM_SPACES      4       /* Num spaces between each bit. */

/*
 * Periodic Interrupt Rates.
 */
static const char *ds1685_rtc_pirq_rate[16] = {
        "none", "3.90625ms", "7.8125ms", "0.122070ms", "0.244141ms",
        "0.488281ms", "0.9765625ms", "1.953125ms", "3.90625ms", "7.8125ms",
        "15.625ms", "31.25ms", "62.5ms", "125ms", "250ms", "500ms"
};

/*
 * Square-Wave Output Frequencies.
 */
static const char *ds1685_rtc_sqw_freq[16] = {
        "none", "256Hz", "128Hz", "8192Hz", "4096Hz", "2048Hz", "1024Hz",
        "512Hz", "256Hz", "128Hz", "64Hz", "32Hz", "16Hz", "8Hz", "4Hz", "2Hz"
};

/**
 * ds1685_rtc_proc - procfs access function.
 * @dev: pointer to device structure.
 * @seq: pointer to seq_file structure.
 */
static int
ds1685_rtc_proc(struct device *dev, struct seq_file *seq)
{
        struct ds1685_priv *rtc = dev_get_drvdata(dev);
        u8 ctrla, ctrlb, ctrld, ctrl4a, ctrl4b, ssn[8];
        char *model;

        /* Read all the relevant data from the control registers. */
        ds1685_rtc_switch_to_bank1(rtc);
        ds1685_rtc_get_ssn(rtc, ssn);
        ctrla = rtc->read(rtc, RTC_CTRL_A);
        ctrlb = rtc->read(rtc, RTC_CTRL_B);
        ctrld = rtc->read(rtc, RTC_CTRL_D);
        ctrl4a = rtc->read(rtc, RTC_EXT_CTRL_4A);
        ctrl4b = rtc->read(rtc, RTC_EXT_CTRL_4B);
        ds1685_rtc_switch_to_bank0(rtc);

        /* Determine the RTC model. */
        switch (ssn[0]) {
        case RTC_MODEL_DS1685:
                model = "DS1685/DS1687\0";
                break;
        case RTC_MODEL_DS1689:
                model = "DS1689/DS1693\0";
                break;
        case RTC_MODEL_DS17285:
                model = "DS17285/DS17287\0";
                break;
        case RTC_MODEL_DS17485:
                model = "DS17485/DS17487\0";
                break;
        case RTC_MODEL_DS17885:
                model = "DS17885/DS17887\0";
                break;
        default:
                model = "Unknown\0";
                break;
        }

        /* Print out the information. */
        seq_printf(seq,
           "Model\t\t: %s\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"
           "Serial #\t: %8phC\n",
           model,
           ((ctrla & RTC_CTRL_A_DV1) ? "enabled" : "disabled"),
           ((ctrlb & RTC_CTRL_B_2412) ? "24-hour" : "12-hour"),
           ((ctrlb & RTC_CTRL_B_DSE) ? "enabled" : "disabled"),
           ((ctrlb & RTC_CTRL_B_DM) ? "binary" : "BCD"),
           ((ctrld & RTC_CTRL_D_VRT) ? "ok" : "exhausted or n/a"),
           ((ctrl4a & RTC_CTRL_4A_VRT2) ? "ok" : "exhausted or n/a"),
           ((ctrlb & RTC_CTRL_B_UIE) ? "yes" : "no"),
           ((ctrlb & RTC_CTRL_B_PIE) ? "yes" : "no"),
           (!(ctrl4b & RTC_CTRL_4B_E32K) ?
            ds1685_rtc_pirq_rate[(ctrla & RTC_CTRL_A_RS_MASK)] : "none"),
           (!((ctrl4b & RTC_CTRL_4B_E32K)) ?
            ds1685_rtc_sqw_freq[(ctrla & RTC_CTRL_A_RS_MASK)] : "32768Hz"),
           ssn);
        return 0;
}
#else
#define ds1685_rtc_proc NULL
#endif /* CONFIG_PROC_FS */
/* ----------------------------------------------------------------------- */


/* ----------------------------------------------------------------------- */
/* RTC Class operations */

static const struct rtc_class_ops
ds1685_rtc_ops = {
        .proc = ds1685_rtc_proc,
        .read_time = ds1685_rtc_read_time,
        .set_time = ds1685_rtc_set_time,
        .read_alarm = ds1685_rtc_read_alarm,
        .set_alarm = ds1685_rtc_set_alarm,
        .alarm_irq_enable = ds1685_rtc_alarm_irq_enable,
};
/* ----------------------------------------------------------------------- */

static int ds1685_nvram_read(void *priv, unsigned int pos, void *val,
                             size_t size)
{
        struct ds1685_priv *rtc = priv;
        struct mutex *rtc_mutex = &rtc->dev->ops_lock;
        ssize_t count;
        u8 *buf = val;
        int err;

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

        ds1685_rtc_switch_to_bank0(rtc);

        /* Read NVRAM in time and bank0 registers. */
        for (count = 0; size > 0 && pos < NVRAM_TOTAL_SZ_BANK0;
             count++, size--) {
                if (count < NVRAM_SZ_TIME)
                        *buf++ = rtc->read(rtc, (NVRAM_TIME_BASE + pos++));
                else
                        *buf++ = rtc->read(rtc, (NVRAM_BANK0_BASE + pos++));
        }

#ifndef CONFIG_RTC_DRV_DS1689
        if (size > 0) {
                ds1685_rtc_switch_to_bank1(rtc);

#ifndef CONFIG_RTC_DRV_DS1685
                /* Enable burst-mode on DS17x85/DS17x87 */
                rtc->write(rtc, RTC_EXT_CTRL_4A,
                           (rtc->read(rtc, RTC_EXT_CTRL_4A) |
                            RTC_CTRL_4A_BME));

                /* We need one write to RTC_BANK1_RAM_ADDR_LSB to start
                 * reading with burst-mode */
                rtc->write(rtc, RTC_BANK1_RAM_ADDR_LSB,
                           (pos - NVRAM_TOTAL_SZ_BANK0));
#endif

                /* Read NVRAM in bank1 registers. */
                for (count = 0; size > 0 && pos < NVRAM_TOTAL_SZ;
                     count++, size--) {
#ifdef CONFIG_RTC_DRV_DS1685
                        /* DS1685/DS1687 has to write to RTC_BANK1_RAM_ADDR
                         * before each read. */
                        rtc->write(rtc, RTC_BANK1_RAM_ADDR,
                                   (pos - NVRAM_TOTAL_SZ_BANK0));
#endif
                        *buf++ = rtc->read(rtc, RTC_BANK1_RAM_DATA_PORT);
                        pos++;
                }

#ifndef CONFIG_RTC_DRV_DS1685
                /* Disable burst-mode on DS17x85/DS17x87 */
                rtc->write(rtc, RTC_EXT_CTRL_4A,
                           (rtc->read(rtc, RTC_EXT_CTRL_4A) &
                            ~(RTC_CTRL_4A_BME)));
#endif
                ds1685_rtc_switch_to_bank0(rtc);
        }
#endif /* !CONFIG_RTC_DRV_DS1689 */
        mutex_unlock(rtc_mutex);

        return 0;
}

static int ds1685_nvram_write(void *priv, unsigned int pos, void *val,
                              size_t size)
{
        struct ds1685_priv *rtc = priv;
        struct mutex *rtc_mutex = &rtc->dev->ops_lock;
        ssize_t count;
        u8 *buf = val;
        int err;

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

        ds1685_rtc_switch_to_bank0(rtc);

        /* Write NVRAM in time and bank0 registers. */
        for (count = 0; size > 0 && pos < NVRAM_TOTAL_SZ_BANK0;
             count++, size--)
                if (count < NVRAM_SZ_TIME)
                        rtc->write(rtc, (NVRAM_TIME_BASE + pos++),
                                   *buf++);
                else
                        rtc->write(rtc, (NVRAM_BANK0_BASE), *buf++);

#ifndef CONFIG_RTC_DRV_DS1689
        if (size > 0) {
                ds1685_rtc_switch_to_bank1(rtc);

#ifndef CONFIG_RTC_DRV_DS1685
                /* Enable burst-mode on DS17x85/DS17x87 */
                rtc->write(rtc, RTC_EXT_CTRL_4A,
                           (rtc->read(rtc, RTC_EXT_CTRL_4A) |
                            RTC_CTRL_4A_BME));

                /* We need one write to RTC_BANK1_RAM_ADDR_LSB to start
                 * writing with burst-mode */
                rtc->write(rtc, RTC_BANK1_RAM_ADDR_LSB,
                           (pos - NVRAM_TOTAL_SZ_BANK0));
#endif

                /* Write NVRAM in bank1 registers. */
                for (count = 0; size > 0 && pos < NVRAM_TOTAL_SZ;
                     count++, size--) {
#ifdef CONFIG_RTC_DRV_DS1685
                        /* DS1685/DS1687 has to write to RTC_BANK1_RAM_ADDR
                         * before each read. */
                        rtc->write(rtc, RTC_BANK1_RAM_ADDR,
                                   (pos - NVRAM_TOTAL_SZ_BANK0));
#endif
                        rtc->write(rtc, RTC_BANK1_RAM_DATA_PORT, *buf++);
                        pos++;
                }

#ifndef CONFIG_RTC_DRV_DS1685
                /* Disable burst-mode on DS17x85/DS17x87 */
                rtc->write(rtc, RTC_EXT_CTRL_4A,
                           (rtc->read(rtc, RTC_EXT_CTRL_4A) &
                            ~(RTC_CTRL_4A_BME)));
#endif
                ds1685_rtc_switch_to_bank0(rtc);
        }
#endif /* !CONFIG_RTC_DRV_DS1689 */
        mutex_unlock(rtc_mutex);

        return 0;
}

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

/**
 * ds1685_rtc_sysfs_battery_show - sysfs file for main battery status.
 * @dev: pointer to device structure.
 * @attr: pointer to device_attribute structure.
 * @buf: pointer to char array to hold the output.
 */
static ssize_t
ds1685_rtc_sysfs_battery_show(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        struct ds1685_priv *rtc = dev_get_drvdata(dev->parent);
        u8 ctrld;

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

        return sprintf(buf, "%s\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 ds1685_priv *rtc = dev_get_drvdata(dev->parent);
        u8 ctrl4a;

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

        return sprintf(buf, "%s\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 ds1685_priv *rtc = dev_get_drvdata(dev->parent);
        u8 ssn[8];

        ds1685_rtc_switch_to_bank1(rtc);
        ds1685_rtc_get_ssn(rtc, ssn);
        ds1685_rtc_switch_to_bank0(rtc);

        return sprintf(buf, "%8phC\n", ssn);
}
static DEVICE_ATTR(serial, S_IRUGO, ds1685_rtc_sysfs_serial_show, NULL);

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

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

/* ----------------------------------------------------------------------- */
/* Driver Probe/Removal */

/**
 * ds1685_rtc_probe - initializes rtc driver.
 * @pdev: pointer to platform_device structure.
 */
static int
ds1685_rtc_probe(struct platform_device *pdev)
{
        struct rtc_device *rtc_dev;
        struct ds1685_priv *rtc;
        struct ds1685_rtc_platform_data *pdata;
        u8 ctrla, ctrlb, hours;
        unsigned char am_pm;
        int ret = 0;
        struct nvmem_config nvmem_cfg = {
                .name = "ds1685_nvram",
                .size = NVRAM_TOTAL_SZ,
                .reg_read = ds1685_nvram_read,
                .reg_write = ds1685_nvram_write,
        };

        /* Get the platform data. */
        pdata = (struct ds1685_rtc_platform_data *) pdev->dev.platform_data;
        if (!pdata)
                return -ENODEV;

        /* Allocate memory for the rtc device. */
        rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
        if (!rtc)
                return -ENOMEM;

        /* Setup resources and access functions */
        switch (pdata->access_type) {
        case ds1685_reg_direct:
                rtc->regs = devm_platform_ioremap_resource(pdev, 0);
                if (IS_ERR(rtc->regs))
                        return PTR_ERR(rtc->regs);
                rtc->read = ds1685_read;
                rtc->write = ds1685_write;
                break;
        case ds1685_reg_indirect:
                rtc->regs = devm_platform_ioremap_resource(pdev, 0);
                if (IS_ERR(rtc->regs))
                        return PTR_ERR(rtc->regs);
                rtc->data = devm_platform_ioremap_resource(pdev, 1);
                if (IS_ERR(rtc->data))
                        return PTR_ERR(rtc->data);
                rtc->read = ds1685_indirect_read;
                rtc->write = ds1685_indirect_write;
                break;
        }

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

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

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

        /* Platform wake_alarm function, if defined. */
        if (pdata->plat_wake_alarm)
                rtc->wake_alarm = pdata->plat_wake_alarm;

        /* Platform post_ram_clear function, if defined. */
        if (pdata->plat_post_ram_clear)
                rtc->post_ram_clear = pdata->plat_post_ram_clear;

        /* set the driver data. */
        platform_set_drvdata(pdev, rtc);

        /* Turn the oscillator on if is not already on (DV1 = 1). */
        ctrla = rtc->read(rtc, RTC_CTRL_A);
        if (!(ctrla & RTC_CTRL_A_DV1))
                ctrla |= RTC_CTRL_A_DV1;

        /* Enable the countdown chain (DV2 = 0) */
        ctrla &= ~(RTC_CTRL_A_DV2);

        /* Clear RS3-RS0 in Control A. */
        ctrla &= ~(RTC_CTRL_A_RS_MASK);

        /*
         * All done with Control A.  Switch to Bank 1 for the remainder of
         * the RTC setup so we have access to the extended functions.
         */
        ctrla |= RTC_CTRL_A_DV0;
        rtc->write(rtc, RTC_CTRL_A, ctrla);

        /* Default to 32768kHz output. */
        rtc->write(rtc, RTC_EXT_CTRL_4B,
                   (rtc->read(rtc, RTC_EXT_CTRL_4B) | RTC_CTRL_4B_E32K));

        /* Set the SET bit in Control B so we can do some housekeeping. */
        rtc->write(rtc, RTC_CTRL_B,
                   (rtc->read(rtc, RTC_CTRL_B) | RTC_CTRL_B_SET));

        /* Read Ext Ctrl 4A and check the INCR bit to avoid a lockout. */
        while (rtc->read(rtc, RTC_EXT_CTRL_4A) & RTC_CTRL_4A_INCR)
                cpu_relax();

        /*
         * If the platform supports BCD mode, then set DM=0 in Control B.
         * Otherwise, set DM=1 for BIN mode.
         */
        ctrlb = rtc->read(rtc, RTC_CTRL_B);
        if (pdata->bcd_mode)
                ctrlb &= ~(RTC_CTRL_B_DM);
        else
                ctrlb |= RTC_CTRL_B_DM;
        rtc->bcd_mode = pdata->bcd_mode;

        /*
         * Disable Daylight Savings Time (DSE = 0).
         * The RTC has hardcoded timezone information that is rendered
         * obselete.  We'll let the OS deal with DST settings instead.
         */
        if (ctrlb & RTC_CTRL_B_DSE)
                ctrlb &= ~(RTC_CTRL_B_DSE);

        /* Force 24-hour mode (2412 = 1). */
        if (!(ctrlb & RTC_CTRL_B_2412)) {
                /* Reinitialize the time hours. */
                hours = rtc->read(rtc, RTC_HRS);
                am_pm = hours & RTC_HRS_AMPM_MASK;
                hours = ds1685_rtc_bcd2bin(rtc, hours, RTC_HRS_12_BCD_MASK,
                                           RTC_HRS_12_BIN_MASK);
                hours = ((hours == 12) ? 0 : ((am_pm) ? hours + 12 : hours));

                /* Enable 24-hour mode. */
                ctrlb |= RTC_CTRL_B_2412;

                /* Write back to Control B, including DM & DSE bits. */
                rtc->write(rtc, RTC_CTRL_B, ctrlb);

                /* Write the time hours back. */
                rtc->write(rtc, RTC_HRS,
                           ds1685_rtc_bin2bcd(rtc, hours,
                                              RTC_HRS_24_BIN_MASK,
                                              RTC_HRS_24_BCD_MASK));

                /* Reinitialize the alarm hours. */
                hours = rtc->read(rtc, RTC_HRS_ALARM);
                am_pm = hours & RTC_HRS_AMPM_MASK;
                hours = ds1685_rtc_bcd2bin(rtc, hours, RTC_HRS_12_BCD_MASK,
                                           RTC_HRS_12_BIN_MASK);
                hours = ((hours == 12) ? 0 : ((am_pm) ? hours + 12 : hours));

                /* Write the alarm hours back. */
                rtc->write(rtc, RTC_HRS_ALARM,
                           ds1685_rtc_bin2bcd(rtc, hours,
                                              RTC_HRS_24_BIN_MASK,
                                              RTC_HRS_24_BCD_MASK));
        } else {
                /* 24-hour mode is already set, so write Control B back. */
                rtc->write(rtc, RTC_CTRL_B, ctrlb);
        }

        /* Unset the SET bit in Control B so the RTC can update. */
        rtc->write(rtc, RTC_CTRL_B,
                   (rtc->read(rtc, RTC_CTRL_B) & ~(RTC_CTRL_B_SET)));

        /* Check the main battery. */
        if (!(rtc->read(rtc, RTC_CTRL_D) & RTC_CTRL_D_VRT))
                dev_warn(&pdev->dev,
                         "Main battery is exhausted! RTC may be invalid!\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));

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

        rtc_dev->ops = &ds1685_rtc_ops;

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

        /* Maximum periodic rate is 8192Hz (0.122070ms). */
        rtc_dev->max_user_freq = RTC_MAX_USER_FREQ;

        /* See if the platform doesn't support UIE. */
        if (pdata->uie_unsupported)
                clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc_dev->features);

        rtc->dev = rtc_dev;

        /*
         * Fetch the IRQ and setup the interrupt handler.
         *
         * Not all platforms have the IRQF pin tied to something.  If not, the
         * RTC will still set the *IE / *F flags and raise IRQF in ctrlc, but
         * there won't be an automatic way of notifying the kernel about it,
         * unless ctrlc is explicitly polled.
         */
        rtc->irq_num = platform_get_irq(pdev, 0);
        if (rtc->irq_num <= 0) {
                clear_bit(RTC_FEATURE_ALARM, rtc_dev->features);
        } else {
                /* Request an IRQ. */
                ret = devm_request_threaded_irq(&pdev->dev, rtc->irq_num,
                                       NULL, ds1685_rtc_irq_handler,
                                       IRQF_SHARED | IRQF_ONESHOT,
                                       pdev->name, pdev);

                /* Check to see if something came back. */
                if (unlikely(ret)) {
                        dev_warn(&pdev->dev,
                                 "RTC interrupt not available\n");
                        rtc->irq_num = 0;
                }
        }

        /* Setup complete. */
        ds1685_rtc_switch_to_bank0(rtc);

        ret = rtc_add_group(rtc_dev, &ds1685_rtc_sysfs_misc_grp);
        if (ret)
                return ret;

        nvmem_cfg.priv = rtc;
        ret = devm_rtc_nvmem_register(rtc_dev, &nvmem_cfg);
        if (ret)
                return ret;

        return devm_rtc_register_device(rtc_dev);
}

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

        /* Read Ctrl B and clear PIE/AIE/UIE. */
        rtc->write(rtc, RTC_CTRL_B,
                   (rtc->read(rtc, RTC_CTRL_B) &
                    ~(RTC_CTRL_B_PAU_MASK)));

        /* Reading Ctrl C auto-clears PF/AF/UF. */
        rtc->read(rtc, RTC_CTRL_C);

        /* Read Ctrl 4B and clear RIE/WIE/KSE. */
        rtc->write(rtc, RTC_EXT_CTRL_4B,
                   (rtc->read(rtc, RTC_EXT_CTRL_4B) &
                    ~(RTC_CTRL_4B_RWK_MASK)));

        /* Manually clear RF/WF/KF in Ctrl 4A. */
        rtc->write(rtc, RTC_EXT_CTRL_4A,
                   (rtc->read(rtc, RTC_EXT_CTRL_4A) &
                    ~(RTC_CTRL_4A_RWK_MASK)));
}

/*
 * ds1685_rtc_driver - rtc driver properties.
 */
static struct platform_driver ds1685_rtc_driver = {
        .driver         = {
                .name   = "rtc-ds1685",
        },
        .probe          = ds1685_rtc_probe,
        .remove         = ds1685_rtc_remove,
};
module_platform_driver(ds1685_rtc_driver);
/* ----------------------------------------------------------------------- */


/* ----------------------------------------------------------------------- */
/* Poweroff function */

/**
 * ds1685_rtc_poweroff - uses the RTC chip to power the system off.
 * @pdev: pointer to platform_device structure.
 */
void __noreturn
ds1685_rtc_poweroff(struct platform_device *pdev)
{
        u8 ctrla, ctrl4a, ctrl4b;
        struct ds1685_priv *rtc;

        /* Check for valid RTC data, else, spin forever. */
        if (unlikely(!pdev)) {
                pr_emerg("platform device data not available, spinning forever ...\n");
                while(1);
                unreachable();
        } else {
                /* Get the rtc data. */
                rtc = platform_get_drvdata(pdev);

                /*
                 * Disable our IRQ.  We're powering down, so we're not
                 * going to worry about cleaning up.  Most of that should
                 * have been taken care of by the shutdown scripts and this
                 * is the final function call.
                 */
                if (rtc->irq_num)
                        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. */
                while(1);
                unreachable();
        }
}
EXPORT_SYMBOL_GPL(ds1685_rtc_poweroff);
/* ----------------------------------------------------------------------- */


MODULE_AUTHOR("Joshua Kinard <kumba@gentoo.org>");
MODULE_AUTHOR("Matthias Fuchs <matthias.fuchs@esd-electronics.com>");
MODULE_DESCRIPTION("Dallas/Maxim DS1685/DS1687-series RTC driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:rtc-ds1685");