/*
 * rtc-ab-b5ze-s3 - Driver for Abracon AB-RTCMC-32.768Khz-B5ZE-S3
 *                  I2C RTC / Alarm chip
 *
 * Copyright (C) 2014, Arnaud EBALARD <arno@natisbad.org>
 *
 * Detailed datasheet of the chip is available here:
 *
 *  http://www.abracon.com/realtimeclock/AB-RTCMC-32.768kHz-B5ZE-S3-Application-Manual.pdf
 *
 * This work is based on ISL12057 driver (drivers/rtc/rtc-isl12057.c).
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/rtc.h>
#include <linux/i2c.h>
#include <linux/bcd.h>
#include <linux/of.h>
#include <linux/regmap.h>
#include <linux/interrupt.h>

#define DRV_NAME "rtc-ab-b5ze-s3"

/* Control section */
#define ABB5ZES3_REG_CTRL1         0x00    /* Control 1 register */
#define ABB5ZES3_REG_CTRL1_CIE     BIT(0)  /* Pulse interrupt enable */
#define ABB5ZES3_REG_CTRL1_AIE     BIT(1)  /* Alarm interrupt enable */
#define ABB5ZES3_REG_CTRL1_SIE     BIT(2)  /* Second interrupt enable */
#define ABB5ZES3_REG_CTRL1_PM      BIT(3)  /* 24h/12h mode */
#define ABB5ZES3_REG_CTRL1_SR      BIT(4)  /* Software reset */
#define ABB5ZES3_REG_CTRL1_STOP    BIT(5)  /* RTC circuit enable */
#define ABB5ZES3_REG_CTRL1_CAP     BIT(7)

#define ABB5ZES3_REG_CTRL2         0x01    /* Control 2 register */
#define ABB5ZES3_REG_CTRL2_CTBIE   BIT(0)  /* Countdown timer B int. enable */
#define ABB5ZES3_REG_CTRL2_CTAIE   BIT(1)  /* Countdown timer A int. enable */
#define ABB5ZES3_REG_CTRL2_WTAIE   BIT(2)  /* Watchdog timer A int. enable */
#define ABB5ZES3_REG_CTRL2_AF      BIT(3)  /* Alarm interrupt status */
#define ABB5ZES3_REG_CTRL2_SF      BIT(4)  /* Second interrupt status */
#define ABB5ZES3_REG_CTRL2_CTBF    BIT(5)  /* Countdown timer B int. status */
#define ABB5ZES3_REG_CTRL2_CTAF    BIT(6)  /* Countdown timer A int. status */
#define ABB5ZES3_REG_CTRL2_WTAF    BIT(7)  /* Watchdog timer A int. status */

#define ABB5ZES3_REG_CTRL3         0x02    /* Control 3 register */
#define ABB5ZES3_REG_CTRL3_PM2     BIT(7)  /* Power Management bit 2 */
#define ABB5ZES3_REG_CTRL3_PM1     BIT(6)  /* Power Management bit 1 */
#define ABB5ZES3_REG_CTRL3_PM0     BIT(5)  /* Power Management bit 0 */
#define ABB5ZES3_REG_CTRL3_BSF     BIT(3)  /* Battery switchover int. status */
#define ABB5ZES3_REG_CTRL3_BLF     BIT(2)  /* Battery low int. status */
#define ABB5ZES3_REG_CTRL3_BSIE    BIT(1)  /* Battery switchover int. enable */
#define ABB5ZES3_REG_CTRL3_BLIE    BIT(0)  /* Battery low int. enable */

#define ABB5ZES3_CTRL_SEC_LEN      3

/* RTC section */
#define ABB5ZES3_REG_RTC_SC        0x03    /* RTC Seconds register */
#define ABB5ZES3_REG_RTC_SC_OSC    BIT(7)  /* Clock integrity status */
#define ABB5ZES3_REG_RTC_MN        0x04    /* RTC Minutes register */
#define ABB5ZES3_REG_RTC_HR        0x05    /* RTC Hours register */
#define ABB5ZES3_REG_RTC_HR_PM     BIT(5)  /* RTC Hours PM bit */
#define ABB5ZES3_REG_RTC_DT        0x06    /* RTC Date register */
#define ABB5ZES3_REG_RTC_DW        0x07    /* RTC Day of the week register */
#define ABB5ZES3_REG_RTC_MO        0x08    /* RTC Month register */
#define ABB5ZES3_REG_RTC_YR        0x09    /* RTC Year register */

#define ABB5ZES3_RTC_SEC_LEN       7

/* Alarm section (enable bits are all active low) */
#define ABB5ZES3_REG_ALRM_MN       0x0A    /* Alarm - minute register */
#define ABB5ZES3_REG_ALRM_MN_AE    BIT(7)  /* Minute enable */
#define ABB5ZES3_REG_ALRM_HR       0x0B    /* Alarm - hours register */
#define ABB5ZES3_REG_ALRM_HR_AE    BIT(7)  /* Hour enable */
#define ABB5ZES3_REG_ALRM_DT       0x0C    /* Alarm - date register */
#define ABB5ZES3_REG_ALRM_DT_AE    BIT(7)  /* Date (day of the month) enable */
#define ABB5ZES3_REG_ALRM_DW       0x0D    /* Alarm - day of the week reg. */
#define ABB5ZES3_REG_ALRM_DW_AE    BIT(7)  /* Day of the week enable */

#define ABB5ZES3_ALRM_SEC_LEN      4

/* Frequency offset section */
#define ABB5ZES3_REG_FREQ_OF       0x0E    /* Frequency offset register */
#define ABB5ZES3_REG_FREQ_OF_MODE  0x0E    /* Offset mode: 2 hours / minute */

/* CLOCKOUT section */
#define ABB5ZES3_REG_TIM_CLK       0x0F    /* Timer & Clockout register */
#define ABB5ZES3_REG_TIM_CLK_TAM   BIT(7)  /* Permanent/pulsed timer A/int. 2 */
#define ABB5ZES3_REG_TIM_CLK_TBM   BIT(6)  /* Permanent/pulsed timer B */
#define ABB5ZES3_REG_TIM_CLK_COF2  BIT(5)  /* Clkout Freq bit 2 */
#define ABB5ZES3_REG_TIM_CLK_COF1  BIT(4)  /* Clkout Freq bit 1 */
#define ABB5ZES3_REG_TIM_CLK_COF0  BIT(3)  /* Clkout Freq bit 0 */
#define ABB5ZES3_REG_TIM_CLK_TAC1  BIT(2)  /* Timer A: - 01 : countdown */
#define ABB5ZES3_REG_TIM_CLK_TAC0  BIT(1)  /*          - 10 : timer     */
#define ABB5ZES3_REG_TIM_CLK_TBC   BIT(0)  /* Timer B enable */

/* Timer A Section */
#define ABB5ZES3_REG_TIMA_CLK      0x10    /* Timer A clock register */
#define ABB5ZES3_REG_TIMA_CLK_TAQ2 BIT(2)  /* Freq bit 2 */
#define ABB5ZES3_REG_TIMA_CLK_TAQ1 BIT(1)  /* Freq bit 1 */
#define ABB5ZES3_REG_TIMA_CLK_TAQ0 BIT(0)  /* Freq bit 0 */
#define ABB5ZES3_REG_TIMA          0x11    /* Timer A register */

#define ABB5ZES3_TIMA_SEC_LEN      2

/* Timer B Section */
#define ABB5ZES3_REG_TIMB_CLK      0x12    /* Timer B clock register */
#define ABB5ZES3_REG_TIMB_CLK_TBW2 BIT(6)
#define ABB5ZES3_REG_TIMB_CLK_TBW1 BIT(5)
#define ABB5ZES3_REG_TIMB_CLK_TBW0 BIT(4)
#define ABB5ZES3_REG_TIMB_CLK_TAQ2 BIT(2)
#define ABB5ZES3_REG_TIMB_CLK_TAQ1 BIT(1)
#define ABB5ZES3_REG_TIMB_CLK_TAQ0 BIT(0)
#define ABB5ZES3_REG_TIMB          0x13    /* Timer B register */
#define ABB5ZES3_TIMB_SEC_LEN      2

#define ABB5ZES3_MEM_MAP_LEN       0x14

struct abb5zes3_rtc_data {
        struct rtc_device *rtc;
        struct regmap *regmap;
        struct mutex lock;

        int irq;

        bool battery_low;
        bool timer_alarm; /* current alarm is via timer A */
};

/*
 * Try and match register bits w/ fixed null values to see whether we
 * are dealing with an ABB5ZES3. Note: this function is called early
 * during init and hence does need mutex protection.
 */
static int abb5zes3_i2c_validate_chip(struct regmap *regmap)
{
        u8 regs[ABB5ZES3_MEM_MAP_LEN];
        static const u8 mask[ABB5ZES3_MEM_MAP_LEN] = { 0x00, 0x00, 0x10, 0x00,
                                                       0x80, 0xc0, 0xc0, 0xf8,
                                                       0xe0, 0x00, 0x00, 0x40,
                                                       0x40, 0x78, 0x00, 0x00,
                                                       0xf8, 0x00, 0x88, 0x00 };
        int ret, i;

        ret = regmap_bulk_read(regmap, 0, regs, ABB5ZES3_MEM_MAP_LEN);
        if (ret)
                return ret;

        for (i = 0; i < ABB5ZES3_MEM_MAP_LEN; ++i) {
                if (regs[i] & mask[i]) /* check if bits are cleared */
                        return -ENODEV;
        }

        return 0;
}

/* Clear alarm status bit. */
static int _abb5zes3_rtc_clear_alarm(struct device *dev)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        int ret;

        ret = regmap_update_bits(data->regmap, ABB5ZES3_REG_CTRL2,
                                 ABB5ZES3_REG_CTRL2_AF, 0);
        if (ret)
                dev_err(dev, "%s: clearing alarm failed (%d)\n", __func__, ret);

        return ret;
}

/* Enable or disable alarm (i.e. alarm interrupt generation) */
static int _abb5zes3_rtc_update_alarm(struct device *dev, bool enable)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        int ret;

        ret = regmap_update_bits(data->regmap, ABB5ZES3_REG_CTRL1,
                                 ABB5ZES3_REG_CTRL1_AIE,
                                 enable ? ABB5ZES3_REG_CTRL1_AIE : 0);
        if (ret)
                dev_err(dev, "%s: writing alarm INT failed (%d)\n",
                        __func__, ret);

        return ret;
}

/* Enable or disable timer (watchdog timer A interrupt generation) */
static int _abb5zes3_rtc_update_timer(struct device *dev, bool enable)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        int ret;

        ret = regmap_update_bits(data->regmap, ABB5ZES3_REG_CTRL2,
                                 ABB5ZES3_REG_CTRL2_WTAIE,
                                 enable ? ABB5ZES3_REG_CTRL2_WTAIE : 0);
        if (ret)
                dev_err(dev, "%s: writing timer INT failed (%d)\n",
                        __func__, ret);

        return ret;
}

/*
 * Note: we only read, so regmap inner lock protection is sufficient, i.e.
 * we do not need driver's main lock protection.
 */
static int _abb5zes3_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        u8 regs[ABB5ZES3_REG_RTC_SC + ABB5ZES3_RTC_SEC_LEN];
        int ret = 0;

        /*
         * As we need to read CTRL1 register anyway to access 24/12h
         * mode bit, we do a single bulk read of both control and RTC
         * sections (they are consecutive). This also ease indexing
         * of register values after bulk read.
         */
        ret = regmap_bulk_read(data->regmap, ABB5ZES3_REG_CTRL1, regs,
                               sizeof(regs));
        if (ret) {
                dev_err(dev, "%s: reading RTC time failed (%d)\n",
                        __func__, ret);
                goto err;
        }

        /* If clock integrity is not guaranteed, do not return a time value */
        if (regs[ABB5ZES3_REG_RTC_SC] & ABB5ZES3_REG_RTC_SC_OSC) {
                ret = -ENODATA;
                goto err;
        }

        tm->tm_sec = bcd2bin(regs[ABB5ZES3_REG_RTC_SC] & 0x7F);
        tm->tm_min = bcd2bin(regs[ABB5ZES3_REG_RTC_MN]);

        if (regs[ABB5ZES3_REG_CTRL1] & ABB5ZES3_REG_CTRL1_PM) { /* 12hr mode */
                tm->tm_hour = bcd2bin(regs[ABB5ZES3_REG_RTC_HR] & 0x1f);
                if (regs[ABB5ZES3_REG_RTC_HR] & ABB5ZES3_REG_RTC_HR_PM) /* PM */
                        tm->tm_hour += 12;
        } else {                                                /* 24hr mode */
                tm->tm_hour = bcd2bin(regs[ABB5ZES3_REG_RTC_HR]);
        }

        tm->tm_mday = bcd2bin(regs[ABB5ZES3_REG_RTC_DT]);
        tm->tm_wday = bcd2bin(regs[ABB5ZES3_REG_RTC_DW]);
        tm->tm_mon  = bcd2bin(regs[ABB5ZES3_REG_RTC_MO]) - 1; /* starts at 1 */
        tm->tm_year = bcd2bin(regs[ABB5ZES3_REG_RTC_YR]) + 100;

err:
        return ret;
}

static int abb5zes3_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        u8 regs[ABB5ZES3_REG_RTC_SC + ABB5ZES3_RTC_SEC_LEN];
        int ret;

        regs[ABB5ZES3_REG_RTC_SC] = bin2bcd(tm->tm_sec); /* MSB=0 clears OSC */
        regs[ABB5ZES3_REG_RTC_MN] = bin2bcd(tm->tm_min);
        regs[ABB5ZES3_REG_RTC_HR] = bin2bcd(tm->tm_hour); /* 24-hour format */
        regs[ABB5ZES3_REG_RTC_DT] = bin2bcd(tm->tm_mday);
        regs[ABB5ZES3_REG_RTC_DW] = bin2bcd(tm->tm_wday);
        regs[ABB5ZES3_REG_RTC_MO] = bin2bcd(tm->tm_mon + 1);
        regs[ABB5ZES3_REG_RTC_YR] = bin2bcd(tm->tm_year - 100);

        mutex_lock(&data->lock);
        ret = regmap_bulk_write(data->regmap, ABB5ZES3_REG_RTC_SC,
                                regs + ABB5ZES3_REG_RTC_SC,
                                ABB5ZES3_RTC_SEC_LEN);
        mutex_unlock(&data->lock);


        return ret;
}

/*
 * Set provided TAQ and Timer A registers (TIMA_CLK and TIMA) based on
 * given number of seconds.
 */
static inline void sec_to_timer_a(u8 secs, u8 *taq, u8 *timer_a)
{
        *taq = ABB5ZES3_REG_TIMA_CLK_TAQ1; /* 1Hz */
        *timer_a = secs;
}

/*
 * Return current number of seconds in Timer A. As we only use
 * timer A with a 1Hz freq, this is what we expect to have.
 */
static inline int sec_from_timer_a(u8 *secs, u8 taq, u8 timer_a)
{
        if (taq != ABB5ZES3_REG_TIMA_CLK_TAQ1) /* 1Hz */
                return -EINVAL;

        *secs = timer_a;

        return 0;
}

/*
 * Read alarm currently configured via a watchdog timer using timer A. This
 * is done by reading current RTC time and adding remaining timer time.
 */
static int _abb5zes3_rtc_read_timer(struct device *dev,
                                    struct rtc_wkalrm *alarm)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        struct rtc_time rtc_tm, *alarm_tm = &alarm->time;
        u8 regs[ABB5ZES3_TIMA_SEC_LEN + 1];
        unsigned long rtc_secs;
        unsigned int reg;
        u8 timer_secs;
        int ret;

        /*
         * Instead of doing two separate calls, because they are consecutive,
         * we grab both clockout register and Timer A section. The latter is
         * used to decide if timer A is enabled (as a watchdog timer).
         */
        ret = regmap_bulk_read(data->regmap, ABB5ZES3_REG_TIM_CLK, regs,
                               ABB5ZES3_TIMA_SEC_LEN + 1);
        if (ret) {
                dev_err(dev, "%s: reading Timer A section failed (%d)\n",
                        __func__, ret);
                goto err;
        }

        /* get current time ... */
        ret = _abb5zes3_rtc_read_time(dev, &rtc_tm);
        if (ret)
                goto err;

        /* ... convert to seconds ... */
        ret = rtc_tm_to_time(&rtc_tm, &rtc_secs);
        if (ret)
                goto err;

        /* ... add remaining timer A time ... */
        ret = sec_from_timer_a(&timer_secs, regs[1], regs[2]);
        if (ret)
                goto err;

        /* ... and convert back. */
        rtc_time_to_tm(rtc_secs + timer_secs, alarm_tm);

        ret = regmap_read(data->regmap, ABB5ZES3_REG_CTRL2, &reg);
        if (ret) {
                dev_err(dev, "%s: reading ctrl reg failed (%d)\n",
                        __func__, ret);
                goto err;
        }

        alarm->enabled = !!(reg & ABB5ZES3_REG_CTRL2_WTAIE);

err:
        return ret;
}

/* Read alarm currently configured via a RTC alarm registers. */
static int _abb5zes3_rtc_read_alarm(struct device *dev,
                                    struct rtc_wkalrm *alarm)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        struct rtc_time rtc_tm, *alarm_tm = &alarm->time;
        unsigned long rtc_secs, alarm_secs;
        u8 regs[ABB5ZES3_ALRM_SEC_LEN];
        unsigned int reg;
        int ret;

        ret = regmap_bulk_read(data->regmap, ABB5ZES3_REG_ALRM_MN, regs,
                               ABB5ZES3_ALRM_SEC_LEN);
        if (ret) {
                dev_err(dev, "%s: reading alarm section failed (%d)\n",
                        __func__, ret);
                goto err;
        }

        alarm_tm->tm_sec  = 0;
        alarm_tm->tm_min  = bcd2bin(regs[0] & 0x7f);
        alarm_tm->tm_hour = bcd2bin(regs[1] & 0x3f);
        alarm_tm->tm_mday = bcd2bin(regs[2] & 0x3f);
        alarm_tm->tm_wday = -1;

        /*
         * The alarm section does not store year/month. We use the ones in rtc
         * section as a basis and increment month and then year if needed to get
         * alarm after current time.
         */
        ret = _abb5zes3_rtc_read_time(dev, &rtc_tm);
        if (ret)
                goto err;

        alarm_tm->tm_year = rtc_tm.tm_year;
        alarm_tm->tm_mon = rtc_tm.tm_mon;

        ret = rtc_tm_to_time(&rtc_tm, &rtc_secs);
        if (ret)
                goto err;

        ret = rtc_tm_to_time(alarm_tm, &alarm_secs);
        if (ret)
                goto err;

        if (alarm_secs < rtc_secs) {
                if (alarm_tm->tm_mon == 11) {
                        alarm_tm->tm_mon = 0;
                        alarm_tm->tm_year += 1;
                } else {
                        alarm_tm->tm_mon += 1;
                }
        }

        ret = regmap_read(data->regmap, ABB5ZES3_REG_CTRL1, &reg);
        if (ret) {
                dev_err(dev, "%s: reading ctrl reg failed (%d)\n",
                        __func__, ret);
                goto err;
        }

        alarm->enabled = !!(reg & ABB5ZES3_REG_CTRL1_AIE);

err:
        return ret;
}

/*
 * As the Alarm mechanism supported by the chip is only accurate to the
 * minute, we use the watchdog timer mechanism provided by timer A
 * (up to 256 seconds w/ a second accuracy) for low alarm values (below
 * 4 minutes). Otherwise, we use the common alarm mechanism provided
 * by the chip. In order for that to work, we keep track of currently
 * configured timer type via 'timer_alarm' flag in our private data
 * structure.
 */
static int abb5zes3_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        int ret;

        mutex_lock(&data->lock);
        if (data->timer_alarm)
                ret = _abb5zes3_rtc_read_timer(dev, alarm);
        else
                ret = _abb5zes3_rtc_read_alarm(dev, alarm);
        mutex_unlock(&data->lock);

        return ret;
}

/*
 * Set alarm using chip alarm mechanism. It is only accurate to the
 * minute (not the second). The function expects alarm interrupt to
 * be disabled.
 */
static int _abb5zes3_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        struct rtc_time *alarm_tm = &alarm->time;
        unsigned long rtc_secs, alarm_secs;
        u8 regs[ABB5ZES3_ALRM_SEC_LEN];
        struct rtc_time rtc_tm;
        int ret, enable = 1;

        ret = _abb5zes3_rtc_read_time(dev, &rtc_tm);
        if (ret)
                goto err;

        ret = rtc_tm_to_time(&rtc_tm, &rtc_secs);
        if (ret)
                goto err;

        ret = rtc_tm_to_time(alarm_tm, &alarm_secs);
        if (ret)
                goto err;

        /* If alarm time is before current time, disable the alarm */
        if (!alarm->enabled || alarm_secs <= rtc_secs) {
                enable = 0;
        } else {
                /*
                 * Chip only support alarms up to one month in the future. Let's
                 * return an error if we get something after that limit.
                 * Comparison is done by incrementing rtc_tm month field by one
                 * and checking alarm value is still below.
                 */
                if (rtc_tm.tm_mon == 11) { /* handle year wrapping */
                        rtc_tm.tm_mon = 0;
                        rtc_tm.tm_year += 1;
                } else {
                        rtc_tm.tm_mon += 1;
                }

                ret = rtc_tm_to_time(&rtc_tm, &rtc_secs);
                if (ret)
                        goto err;

                if (alarm_secs > rtc_secs) {
                        dev_err(dev, "%s: alarm maximum is one month in the "
                                "future (%d)\n", __func__, ret);
                        ret = -EINVAL;
                        goto err;
                }
        }

        /*
         * Program all alarm registers but DW one. For each register, setting
         * MSB to 0 enables associated alarm.
         */
        regs[0] = bin2bcd(alarm_tm->tm_min) & 0x7f;
        regs[1] = bin2bcd(alarm_tm->tm_hour) & 0x3f;
        regs[2] = bin2bcd(alarm_tm->tm_mday) & 0x3f;
        regs[3] = ABB5ZES3_REG_ALRM_DW_AE; /* do not match day of the week */

        ret = regmap_bulk_write(data->regmap, ABB5ZES3_REG_ALRM_MN, regs,
                                ABB5ZES3_ALRM_SEC_LEN);
        if (ret < 0) {
                dev_err(dev, "%s: writing ALARM section failed (%d)\n",
                        __func__, ret);
                goto err;
        }

        /* Record currently configured alarm is not a timer */
        data->timer_alarm = 0;

        /* Enable or disable alarm interrupt generation */
        ret = _abb5zes3_rtc_update_alarm(dev, enable);

err:
        return ret;
}

/*
 * Set alarm using timer watchdog (via timer A) mechanism. The function expects
 * timer A interrupt to be disabled.
 */
static int _abb5zes3_rtc_set_timer(struct device *dev, struct rtc_wkalrm *alarm,
                                   u8 secs)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        u8 regs[ABB5ZES3_TIMA_SEC_LEN];
        u8 mask = ABB5ZES3_REG_TIM_CLK_TAC0 | ABB5ZES3_REG_TIM_CLK_TAC1;
        int ret = 0;

        /* Program given number of seconds to Timer A registers */
        sec_to_timer_a(secs, &regs[0], &regs[1]);
        ret = regmap_bulk_write(data->regmap, ABB5ZES3_REG_TIMA_CLK, regs,
                                ABB5ZES3_TIMA_SEC_LEN);
        if (ret < 0) {
                dev_err(dev, "%s: writing timer section failed\n", __func__);
                goto err;
        }

        /* Configure Timer A as a watchdog timer */
        ret = regmap_update_bits(data->regmap, ABB5ZES3_REG_TIM_CLK,
                                 mask, ABB5ZES3_REG_TIM_CLK_TAC1);
        if (ret)
                dev_err(dev, "%s: failed to update timer\n", __func__);

        /* Record currently configured alarm is a timer */
        data->timer_alarm = 1;

        /* Enable or disable timer interrupt generation */
        ret = _abb5zes3_rtc_update_timer(dev, alarm->enabled);

err:
        return ret;
}

/*
 * The chip has an alarm which is only accurate to the minute. In order to
 * handle alarms below that limit, we use the watchdog timer function of
 * timer A. More precisely, the timer method is used for alarms below 240
 * seconds.
 */
static int abb5zes3_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        struct rtc_time *alarm_tm = &alarm->time;
        unsigned long rtc_secs, alarm_secs;
        struct rtc_time rtc_tm;
        int ret;

        mutex_lock(&data->lock);
        ret = _abb5zes3_rtc_read_time(dev, &rtc_tm);
        if (ret)
                goto err;

        ret = rtc_tm_to_time(&rtc_tm, &rtc_secs);
        if (ret)
                goto err;

        ret = rtc_tm_to_time(alarm_tm, &alarm_secs);
        if (ret)
                goto err;

        /* Let's first disable both the alarm and the timer interrupts */
        ret = _abb5zes3_rtc_update_alarm(dev, false);
        if (ret < 0) {
                dev_err(dev, "%s: unable to disable alarm (%d)\n", __func__,
                        ret);
                goto err;
        }
        ret = _abb5zes3_rtc_update_timer(dev, false);
        if (ret < 0) {
                dev_err(dev, "%s: unable to disable timer (%d)\n", __func__,
                        ret);
                goto err;
        }

        data->timer_alarm = 0;

        /*
         * Let's now configure the alarm; if we are expected to ring in
         * more than 240s, then we setup an alarm. Otherwise, a timer.
         */
        if ((alarm_secs > rtc_secs) && ((alarm_secs - rtc_secs) <= 240))
                ret = _abb5zes3_rtc_set_timer(dev, alarm,
                                              alarm_secs - rtc_secs);
        else
                ret = _abb5zes3_rtc_set_alarm(dev, alarm);

 err:
        mutex_unlock(&data->lock);

        if (ret)
                dev_err(dev, "%s: unable to configure alarm (%d)\n", __func__,
                        ret);

        return ret;
}

/* Enable or disable battery low irq generation */
static inline int _abb5zes3_rtc_battery_low_irq_enable(struct regmap *regmap,
                                                       bool enable)
{
        return regmap_update_bits(regmap, ABB5ZES3_REG_CTRL3,
                                  ABB5ZES3_REG_CTRL3_BLIE,
                                  enable ? ABB5ZES3_REG_CTRL3_BLIE : 0);
}

/*
 * Check current RTC status and enable/disable what needs to be. Return 0 if
 * everything went ok and a negative value upon error. Note: this function
 * is called early during init and hence does need mutex protection.
 */
static int abb5zes3_rtc_check_setup(struct device *dev)
{
        struct abb5zes3_rtc_data *data = dev_get_drvdata(dev);
        struct regmap *regmap = data->regmap;
        unsigned int reg;
        int ret;
        u8 mask;

        /*
         * By default, the devices generates a 32.768KHz signal on IRQ#1 pin. It
         * is disabled here to prevent polluting the interrupt line and
         * uselessly triggering the IRQ handler we install for alarm and battery
         * low events. Note: this is done before clearing int. status below
         * in this function.
         * We also disable all timers and set timer interrupt to permanent (not
         * pulsed).
         */
        mask = (ABB5ZES3_REG_TIM_CLK_TBC | ABB5ZES3_REG_TIM_CLK_TAC0 |
                ABB5ZES3_REG_TIM_CLK_TAC1 | ABB5ZES3_REG_TIM_CLK_COF0 |
                ABB5ZES3_REG_TIM_CLK_COF1 | ABB5ZES3_REG_TIM_CLK_COF2 |
                ABB5ZES3_REG_TIM_CLK_TBM | ABB5ZES3_REG_TIM_CLK_TAM);
        ret = regmap_update_bits(regmap, ABB5ZES3_REG_TIM_CLK, mask,
                ABB5ZES3_REG_TIM_CLK_COF0 | ABB5ZES3_REG_TIM_CLK_COF1 |
                ABB5ZES3_REG_TIM_CLK_COF2);
        if (ret < 0) {
                dev_err(dev, "%s: unable to initialize clkout register (%d)\n",
                        __func__, ret);
                return ret;
        }

        /*
         * Each component of the alarm (MN, HR, DT, DW) can be enabled/disabled
         * individually by clearing/setting MSB of each associated register. So,
         * we set all alarm enable bits to disable current alarm setting.
         */
        mask = (ABB5ZES3_REG_ALRM_MN_AE | ABB5ZES3_REG_ALRM_HR_AE |
                ABB5ZES3_REG_ALRM_DT_AE | ABB5ZES3_REG_ALRM_DW_AE);
        ret = regmap_update_bits(regmap, ABB5ZES3_REG_CTRL2, mask, mask);
        if (ret < 0) {
                dev_err(dev, "%s: unable to disable alarm setting (%d)\n",
                        __func__, ret);
                return ret;
        }

        /* Set Control 1 register (RTC enabled, 24hr mode, all int. disabled) */
        mask = (ABB5ZES3_REG_CTRL1_CIE | ABB5ZES3_REG_CTRL1_AIE |
                ABB5ZES3_REG_CTRL1_SIE | ABB5ZES3_REG_CTRL1_PM |
                ABB5ZES3_REG_CTRL1_CAP | ABB5ZES3_REG_CTRL1_STOP);
        ret = regmap_update_bits(regmap, ABB5ZES3_REG_CTRL1, mask, 0);
        if (ret < 0) {
                dev_err(dev, "%s: unable to initialize CTRL1 register (%d)\n",
                        __func__, ret);
                return ret;
        }

        /*
         * Set Control 2 register (timer int. disabled, alarm status cleared).
         * WTAF is read-only and cleared automatically by reading the register.
         */
        mask = (ABB5ZES3_REG_CTRL2_CTBIE | ABB5ZES3_REG_CTRL2_CTAIE |
                ABB5ZES3_REG_CTRL2_WTAIE | ABB5ZES3_REG_CTRL2_AF |
                ABB5ZES3_REG_CTRL2_SF | ABB5ZES3_REG_CTRL2_CTBF |
                ABB5ZES3_REG_CTRL2_CTAF);
        ret = regmap_update_bits(regmap, ABB5ZES3_REG_CTRL2, mask, 0);
        if (ret < 0) {
                dev_err(dev, "%s: unable to initialize CTRL2 register (%d)\n",
                        __func__, ret);
                return ret;
        }

        /*
         * Enable battery low detection function and battery switchover function
         * (standard mode). Disable associated interrupts. Clear battery
         * switchover flag but not battery low flag. The latter is checked
         * later below.
         */
        mask = (ABB5ZES3_REG_CTRL3_PM0 | ABB5ZES3_REG_CTRL3_PM1 |
                ABB5ZES3_REG_CTRL3_PM2 | ABB5ZES3_REG_CTRL3_BLIE |
                ABB5ZES3_REG_CTRL3_BSIE| ABB5ZES3_REG_CTRL3_BSF);
        ret = regmap_update_bits(regmap, ABB5ZES3_REG_CTRL3, mask, 0);
        if (ret < 0) {
                dev_err(dev, "%s: unable to initialize CTRL3 register (%d)\n",
                        __func__, ret);
                return ret;
        }

        /* Check oscillator integrity flag */
        ret = regmap_read(regmap, ABB5ZES3_REG_RTC_SC, &reg);
        if (ret < 0) {
                dev_err(dev, "%s: unable to read osc. integrity flag (%d)\n",
                        __func__, ret);
                return ret;
        }

        if (reg & ABB5ZES3_REG_RTC_SC_OSC) {
                dev_err(dev, "clock integrity not guaranteed. Osc. has stopped "
                        "or has been interrupted.\n");
                dev_err(dev, "change battery (if not already done) and  "
                        "then set time to reset osc. failure flag.\n");
        }

        /*
         * Check battery low flag at startup: this allows reporting battery
         * is low at startup when IRQ line is not connected. Note: we record
         * current status to avoid reenabling this interrupt later in probe
         * function if battery is low.
         */
        ret = regmap_read(regmap, ABB5ZES3_REG_CTRL3, &reg);
        if (ret < 0) {
                dev_err(dev, "%s: unable to read battery low flag (%d)\n",
                        __func__, ret);
                return ret;
        }

        data->battery_low = reg & ABB5ZES3_REG_CTRL3_BLF;
        if (data->battery_low) {
                dev_err(dev, "RTC battery is low; please, consider "
                        "changing it!\n");

                ret = _abb5zes3_rtc_battery_low_irq_enable(regmap, false);
                if (ret)
                        dev_err(dev, "%s: disabling battery low interrupt "
                                "generation failed (%d)\n", __func__, ret);
        }

        return ret;
}

static int abb5zes3_rtc_alarm_irq_enable(struct device *dev,
                                         unsigned int enable)
{
        struct abb5zes3_rtc_data *rtc_data = dev_get_drvdata(dev);
        int ret = 0;

        if (rtc_data->irq) {
                mutex_lock(&rtc_data->lock);
                if (rtc_data->timer_alarm)
                        ret = _abb5zes3_rtc_update_timer(dev, enable);
                else
                        ret = _abb5zes3_rtc_update_alarm(dev, enable);
                mutex_unlock(&rtc_data->lock);
        }

        return ret;
}

static irqreturn_t _abb5zes3_rtc_interrupt(int irq, void *data)
{
        struct i2c_client *client = data;
        struct device *dev = &client->dev;
        struct abb5zes3_rtc_data *rtc_data = dev_get_drvdata(dev);
        struct rtc_device *rtc = rtc_data->rtc;
        u8 regs[ABB5ZES3_CTRL_SEC_LEN];
        int ret, handled = IRQ_NONE;

        ret = regmap_bulk_read(rtc_data->regmap, 0, regs,
                               ABB5ZES3_CTRL_SEC_LEN);
        if (ret) {
                dev_err(dev, "%s: unable to read control section (%d)!\n",
                        __func__, ret);
                return handled;
        }

        /*
         * Check battery low detection flag and disable battery low interrupt
         * generation if flag is set (interrupt can only be cleared when
         * battery is replaced).
         */
        if (regs[ABB5ZES3_REG_CTRL3] & ABB5ZES3_REG_CTRL3_BLF) {
                dev_err(dev, "RTC battery is low; please change it!\n");

                _abb5zes3_rtc_battery_low_irq_enable(rtc_data->regmap, false);

                handled = IRQ_HANDLED;
        }

        /* Check alarm flag */
        if (regs[ABB5ZES3_REG_CTRL2] & ABB5ZES3_REG_CTRL2_AF) {
                dev_dbg(dev, "RTC alarm!\n");

                rtc_update_irq(rtc, 1, RTC_IRQF | RTC_AF);

                /* Acknowledge and disable the alarm */
                _abb5zes3_rtc_clear_alarm(dev);
                _abb5zes3_rtc_update_alarm(dev, 0);

                handled = IRQ_HANDLED;
        }

        /* Check watchdog Timer A flag */
        if (regs[ABB5ZES3_REG_CTRL2] & ABB5ZES3_REG_CTRL2_WTAF) {
                dev_dbg(dev, "RTC timer!\n");

                rtc_update_irq(rtc, 1, RTC_IRQF | RTC_AF);

                /*
                 * Acknowledge and disable the alarm. Note: WTAF
                 * flag had been cleared when reading CTRL2
                 */
                _abb5zes3_rtc_update_timer(dev, 0);

                rtc_data->timer_alarm = 0;

                handled = IRQ_HANDLED;
        }

        return handled;
}

static const struct rtc_class_ops rtc_ops = {
        .read_time = _abb5zes3_rtc_read_time,
        .set_time = abb5zes3_rtc_set_time,
        .read_alarm = abb5zes3_rtc_read_alarm,
        .set_alarm = abb5zes3_rtc_set_alarm,
        .alarm_irq_enable = abb5zes3_rtc_alarm_irq_enable,
};

static const struct regmap_config abb5zes3_rtc_regmap_config = {
        .reg_bits = 8,
        .val_bits = 8,
};

static int abb5zes3_probe(struct i2c_client *client,
                          const struct i2c_device_id *id)
{
        struct abb5zes3_rtc_data *data = NULL;
        struct device *dev = &client->dev;
        struct regmap *regmap;
        int ret;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
                                     I2C_FUNC_SMBUS_BYTE_DATA |
                                     I2C_FUNC_SMBUS_I2C_BLOCK)) {
                ret = -ENODEV;
                goto err;
        }

        regmap = devm_regmap_init_i2c(client, &abb5zes3_rtc_regmap_config);
        if (IS_ERR(regmap)) {
                ret = PTR_ERR(regmap);
                dev_err(dev, "%s: regmap allocation failed: %d\n",
                        __func__, ret);
                goto err;
        }

        ret = abb5zes3_i2c_validate_chip(regmap);
        if (ret)
                goto err;

        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data) {
                ret = -ENOMEM;
                goto err;
        }

        mutex_init(&data->lock);
        data->regmap = regmap;
        dev_set_drvdata(dev, data);

        ret = abb5zes3_rtc_check_setup(dev);
        if (ret)
                goto err;

        data->rtc = devm_rtc_allocate_device(dev);
        ret = PTR_ERR_OR_ZERO(data->rtc);
        if (ret) {
                dev_err(dev, "%s: unable to allocate RTC device (%d)\n",
                        __func__, ret);
                goto err;
        }

        if (client->irq > 0) {
                ret = devm_request_threaded_irq(dev, client->irq, NULL,
                                                _abb5zes3_rtc_interrupt,
                                                IRQF_SHARED|IRQF_ONESHOT,
                                                DRV_NAME, client);
                if (!ret) {
                        device_init_wakeup(dev, true);
                        data->irq = client->irq;
                        dev_dbg(dev, "%s: irq %d used by RTC\n", __func__,
                                client->irq);
                } else {
                        dev_err(dev, "%s: irq %d unavailable (%d)\n",
                                __func__, client->irq, ret);
                        goto err;
                }
        }

        data->rtc->ops = &rtc_ops;
        data->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
        data->rtc->range_max = RTC_TIMESTAMP_END_2099;

        /* Enable battery low detection interrupt if battery not already low */
        if (!data->battery_low && data->irq) {
                ret = _abb5zes3_rtc_battery_low_irq_enable(regmap, true);
                if (ret) {
                        dev_err(dev, "%s: enabling battery low interrupt "
                                "generation failed (%d)\n", __func__, ret);
                        goto err;
                }
        }

        ret = rtc_register_device(data->rtc);

err:
        if (ret && data && data->irq)
                device_init_wakeup(dev, false);
        return ret;
}

static int abb5zes3_remove(struct i2c_client *client)
{
        struct abb5zes3_rtc_data *rtc_data = dev_get_drvdata(&client->dev);

        if (rtc_data->irq > 0)
                device_init_wakeup(&client->dev, false);

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int abb5zes3_rtc_suspend(struct device *dev)
{
        struct abb5zes3_rtc_data *rtc_data = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                return enable_irq_wake(rtc_data->irq);

        return 0;
}

static int abb5zes3_rtc_resume(struct device *dev)
{
        struct abb5zes3_rtc_data *rtc_data = dev_get_drvdata(dev);

        if (device_may_wakeup(dev))
                return disable_irq_wake(rtc_data->irq);

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(abb5zes3_rtc_pm_ops, abb5zes3_rtc_suspend,
                         abb5zes3_rtc_resume);

#ifdef CONFIG_OF
static const struct of_device_id abb5zes3_dt_match[] = {
        { .compatible = "abracon,abb5zes3" },
        { },
};
MODULE_DEVICE_TABLE(of, abb5zes3_dt_match);
#endif

static const struct i2c_device_id abb5zes3_id[] = {
        { "abb5zes3", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, abb5zes3_id);

static struct i2c_driver abb5zes3_driver = {
        .driver = {
                .name = DRV_NAME,
                .pm = &abb5zes3_rtc_pm_ops,
                .of_match_table = of_match_ptr(abb5zes3_dt_match),
        },
        .probe    = abb5zes3_probe,
        .remove   = abb5zes3_remove,
        .id_table = abb5zes3_id,
};
module_i2c_driver(abb5zes3_driver);

MODULE_AUTHOR("Arnaud EBALARD <arno@natisbad.org>");
MODULE_DESCRIPTION("Abracon AB-RTCMC-32.768kHz-B5ZE-S3 RTC/Alarm driver");
MODULE_LICENSE("GPL");