// SPDX-License-Identifier: GPL-2.0-only
/*
 * I2C client/driver for the ST M41T80 family of i2c rtc chips.
 *
 * Author: Alexander Bigga <ab@mycable.de>
 *
 * Based on m41t00.c by Mark A. Greer <mgreer@mvista.com>
 *
 * 2006 (c) mycable GmbH
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bcd.h>
#include <linux/clk-provider.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/string.h>
#include <linux/delay.h>
#ifdef CONFIG_RTC_DRV_M41T80_WDT
#include <linux/fs.h>
#include <linux/ioctl.h>
#include <linux/miscdevice.h>
#include <linux/reboot.h>
#include <linux/watchdog.h>
#endif

#define M41T80_REG_SSEC         0x00
#define M41T80_REG_SEC          0x01
#define M41T80_REG_MIN          0x02
#define M41T80_REG_HOUR         0x03
#define M41T80_REG_WDAY         0x04
#define M41T80_REG_DAY          0x05
#define M41T80_REG_MON          0x06
#define M41T80_REG_YEAR         0x07
#define M41T80_REG_ALARM_MON    0x0a
#define M41T80_REG_ALARM_DAY    0x0b
#define M41T80_REG_ALARM_HOUR   0x0c
#define M41T80_REG_ALARM_MIN    0x0d
#define M41T80_REG_ALARM_SEC    0x0e
#define M41T80_REG_FLAGS        0x0f
#define M41T80_REG_SQW          0x13

#define M41T80_DATETIME_REG_SIZE        (M41T80_REG_YEAR + 1)
#define M41T80_ALARM_REG_SIZE   \
        (M41T80_REG_ALARM_SEC + 1 - M41T80_REG_ALARM_MON)

#define M41T80_SQW_MAX_FREQ     32768

#define M41T80_SEC_ST           BIT(7)  /* ST: Stop Bit */
#define M41T80_ALMON_AFE        BIT(7)  /* AFE: AF Enable Bit */
#define M41T80_ALMON_SQWE       BIT(6)  /* SQWE: SQW Enable Bit */
#define M41T80_ALHOUR_HT        BIT(6)  /* HT: Halt Update Bit */
#define M41T80_FLAGS_OF         BIT(2)  /* OF: Oscillator Failure Bit */
#define M41T80_FLAGS_AF         BIT(6)  /* AF: Alarm Flag Bit */
#define M41T80_FLAGS_BATT_LOW   BIT(4)  /* BL: Battery Low Bit */
#define M41T80_WATCHDOG_RB2     BIT(7)  /* RB: Watchdog resolution */
#define M41T80_WATCHDOG_RB1     BIT(1)  /* RB: Watchdog resolution */
#define M41T80_WATCHDOG_RB0     BIT(0)  /* RB: Watchdog resolution */

#define M41T80_FEATURE_HT       BIT(0)  /* Halt feature */
#define M41T80_FEATURE_BL       BIT(1)  /* Battery low indicator */
#define M41T80_FEATURE_SQ       BIT(2)  /* Squarewave feature */
#define M41T80_FEATURE_WD       BIT(3)  /* Extra watchdog resolution */
#define M41T80_FEATURE_SQ_ALT   BIT(4)  /* RSx bits are in reg 4 */

static const struct i2c_device_id m41t80_id[] = {
        { "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT },
        { "m41t65", M41T80_FEATURE_WD },
        { "m41t80", M41T80_FEATURE_SQ },
        { "m41t81", M41T80_FEATURE_HT | M41T80_FEATURE_SQ},
        { "m41t81s", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
        { "m41t82", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
        { "m41t83", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
        { "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
        { "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
        { "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
        { "rv4162", M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT },
        { }
};
MODULE_DEVICE_TABLE(i2c, m41t80_id);

static const __maybe_unused struct of_device_id m41t80_of_match[] = {
        {
                .compatible = "st,m41t62",
                .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT)
        },
        {
                .compatible = "st,m41t65",
                .data = (void *)(M41T80_FEATURE_WD)
        },
        {
                .compatible = "st,m41t80",
                .data = (void *)(M41T80_FEATURE_SQ)
        },
        {
                .compatible = "st,m41t81",
                .data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_SQ)
        },
        {
                .compatible = "st,m41t81s",
                .data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
        },
        {
                .compatible = "st,m41t82",
                .data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
        },
        {
                .compatible = "st,m41t83",
                .data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
        },
        {
                .compatible = "st,m41t84",
                .data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
        },
        {
                .compatible = "st,m41t85",
                .data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
        },
        {
                .compatible = "st,m41t87",
                .data = (void *)(M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ)
        },
        {
                .compatible = "microcrystal,rv4162",
                .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
        },
        /* DT compatibility only, do not use compatibles below: */
        {
                .compatible = "st,rv4162",
                .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
        },
        {
                .compatible = "rv4162",
                .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
        },
        { }
};
MODULE_DEVICE_TABLE(of, m41t80_of_match);

struct m41t80_data {
        unsigned long features;
        struct i2c_client *client;
        struct rtc_device *rtc;
#ifdef CONFIG_COMMON_CLK
        struct clk_hw sqw;
        unsigned long freq;
        unsigned int sqwe;
#endif
};

static irqreturn_t m41t80_handle_irq(int irq, void *dev_id)
{
        struct i2c_client *client = dev_id;
        struct m41t80_data *m41t80 = i2c_get_clientdata(client);
        unsigned long events = 0;
        int flags, flags_afe;

        rtc_lock(m41t80->rtc);

        flags_afe = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
        if (flags_afe < 0) {
                rtc_unlock(m41t80->rtc);
                return IRQ_NONE;
        }

        flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
        if (flags <= 0) {
                rtc_unlock(m41t80->rtc);
                return IRQ_NONE;
        }

        if (flags & M41T80_FLAGS_AF) {
                flags &= ~M41T80_FLAGS_AF;
                flags_afe &= ~M41T80_ALMON_AFE;
                events |= RTC_AF;
        }

        if (events) {
                rtc_update_irq(m41t80->rtc, 1, events);
                i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS, flags);
                i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
                                          flags_afe);
        }

        rtc_unlock(m41t80->rtc);

        return IRQ_HANDLED;
}

static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        unsigned char buf[8];
        int err, flags;

        flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
        if (flags < 0)
                return flags;

        if (flags & M41T80_FLAGS_OF) {
                dev_err(&client->dev, "Oscillator failure, time may not be accurate, write time to RTC to fix it.\n");
                return -EINVAL;
        }

        err = i2c_smbus_read_i2c_block_data(client, M41T80_REG_SSEC,
                                            sizeof(buf), buf);
        if (err < 0) {
                dev_dbg(&client->dev, "Unable to read date\n");
                return err;
        }

        tm->tm_sec = bcd2bin(buf[M41T80_REG_SEC] & 0x7f);
        tm->tm_min = bcd2bin(buf[M41T80_REG_MIN] & 0x7f);
        tm->tm_hour = bcd2bin(buf[M41T80_REG_HOUR] & 0x3f);
        tm->tm_mday = bcd2bin(buf[M41T80_REG_DAY] & 0x3f);
        tm->tm_wday = buf[M41T80_REG_WDAY] & 0x07;
        tm->tm_mon = bcd2bin(buf[M41T80_REG_MON] & 0x1f) - 1;

        /* assume 20YY not 19YY, and ignore the Century Bit */
        tm->tm_year = bcd2bin(buf[M41T80_REG_YEAR]) + 100;
        return 0;
}

static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *in_tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct m41t80_data *clientdata = i2c_get_clientdata(client);
        struct rtc_time tm = *in_tm;
        unsigned char buf[8];
        int err, flags;
        time64_t time = 0;

        flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
        if (flags < 0)
                return flags;
        if (flags & M41T80_FLAGS_OF) {
                /* add 4sec of oscillator stablize time otherwise we are behind 4sec */
                time = rtc_tm_to_time64(&tm);
                rtc_time64_to_tm(time + 4, &tm);
        }
        buf[M41T80_REG_SSEC] = 0;
        buf[M41T80_REG_SEC] = bin2bcd(tm.tm_sec);
        buf[M41T80_REG_MIN] = bin2bcd(tm.tm_min);
        buf[M41T80_REG_HOUR] = bin2bcd(tm.tm_hour);
        buf[M41T80_REG_DAY] = bin2bcd(tm.tm_mday);
        buf[M41T80_REG_MON] = bin2bcd(tm.tm_mon + 1);
        buf[M41T80_REG_YEAR] = bin2bcd(tm.tm_year - 100);
        buf[M41T80_REG_WDAY] = tm.tm_wday;

        /* If the square wave output is controlled in the weekday register */
        if (clientdata->features & M41T80_FEATURE_SQ_ALT) {
                int val;

                val = i2c_smbus_read_byte_data(client, M41T80_REG_WDAY);
                if (val < 0)
                        return val;

                buf[M41T80_REG_WDAY] |= (val & 0xf0);
        }

        err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_SSEC,
                                             sizeof(buf), buf);
        if (err < 0) {
                dev_dbg(&client->dev, "Unable to write to date registers\n");
                return err;
        }
        if (flags & M41T80_FLAGS_OF) {
                /* OF cannot be immediately reset: oscillator has to be restarted. */
                dev_warn(&client->dev, "OF bit is still set, kickstarting clock.\n");
                err = i2c_smbus_write_byte_data(client, M41T80_REG_SEC, M41T80_SEC_ST);
                if (err < 0) {
                        dev_dbg(&client->dev, "Can't set ST bit\n");
                        return err;
                }
                err = i2c_smbus_write_byte_data(client, M41T80_REG_SEC, flags & ~M41T80_SEC_ST);
                if (err < 0) {
                        dev_dbg(&client->dev, "Can't clear ST bit\n");
                        return err;
                }
                /* oscillator must run for 4sec before we attempt to reset OF bit */
                msleep(4000);
                /* Clear the OF bit of Flags Register */
                err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS, flags & ~M41T80_FLAGS_OF);
                if (err < 0) {
                        dev_dbg(&client->dev, "Unable to write flags register\n");
                        return err;
                }
                flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
                if (flags < 0) {
                        return flags;
                } else if (flags & M41T80_FLAGS_OF) {
                        dev_dbg(&client->dev, "Can't clear the OF bit check battery\n");
                        return err;
                }
        }

        return err;
}

static int m41t80_rtc_proc(struct device *dev, struct seq_file *seq)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct m41t80_data *clientdata = i2c_get_clientdata(client);
        int reg;

        if (clientdata->features & M41T80_FEATURE_BL) {
                reg = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
                if (reg < 0)
                        return reg;
                seq_printf(seq, "battery\t\t: %s\n",
                           (reg & M41T80_FLAGS_BATT_LOW) ? "exhausted" : "ok");
        }
        return 0;
}

static int m41t80_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct i2c_client *client = to_i2c_client(dev);
        int flags, retval;

        flags = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
        if (flags < 0)
                return flags;

        if (enabled)
                flags |= M41T80_ALMON_AFE;
        else
                flags &= ~M41T80_ALMON_AFE;

        retval = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, flags);
        if (retval < 0) {
                dev_dbg(dev, "Unable to enable alarm IRQ %d\n", retval);
                return retval;
        }
        return 0;
}

static int m41t80_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct i2c_client *client = to_i2c_client(dev);
        u8 alarmvals[5];
        int ret, err;

        alarmvals[0] = bin2bcd(alrm->time.tm_mon + 1);
        alarmvals[1] = bin2bcd(alrm->time.tm_mday);
        alarmvals[2] = bin2bcd(alrm->time.tm_hour);
        alarmvals[3] = bin2bcd(alrm->time.tm_min);
        alarmvals[4] = bin2bcd(alrm->time.tm_sec);

        /* Clear AF and AFE flags */
        ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
        if (ret < 0)
                return ret;
        err = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
                                        ret & ~(M41T80_ALMON_AFE));
        if (err < 0) {
                dev_dbg(dev, "Unable to clear AFE bit\n");
                return err;
        }

        /* Keep SQWE bit value */
        alarmvals[0] |= (ret & M41T80_ALMON_SQWE);

        ret = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
        if (ret < 0)
                return ret;

        err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS,
                                        ret & ~(M41T80_FLAGS_AF));
        if (err < 0) {
                dev_dbg(dev, "Unable to clear AF bit\n");
                return err;
        }

        /* Write the alarm */
        err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_ALARM_MON,
                                             5, alarmvals);
        if (err)
                return err;

        /* Enable the alarm interrupt */
        if (alrm->enabled) {
                alarmvals[0] |= M41T80_ALMON_AFE;
                err = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
                                                alarmvals[0]);
                if (err)
                        return err;
        }

        return 0;
}

static int m41t80_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
        struct i2c_client *client = to_i2c_client(dev);
        u8 alarmvals[5];
        int flags, ret;

        ret = i2c_smbus_read_i2c_block_data(client, M41T80_REG_ALARM_MON,
                                            5, alarmvals);
        if (ret != 5)
                return ret < 0 ? ret : -EIO;

        flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
        if (flags < 0)
                return flags;

        alrm->time.tm_sec  = bcd2bin(alarmvals[4] & 0x7f);
        alrm->time.tm_min  = bcd2bin(alarmvals[3] & 0x7f);
        alrm->time.tm_hour = bcd2bin(alarmvals[2] & 0x3f);
        alrm->time.tm_mday = bcd2bin(alarmvals[1] & 0x3f);
        alrm->time.tm_mon  = bcd2bin(alarmvals[0] & 0x3f) - 1;

        alrm->enabled = !!(alarmvals[0] & M41T80_ALMON_AFE);
        alrm->pending = (flags & M41T80_FLAGS_AF) && alrm->enabled;

        return 0;
}

static const struct rtc_class_ops m41t80_rtc_ops = {
        .read_time = m41t80_rtc_read_time,
        .set_time = m41t80_rtc_set_time,
        .proc = m41t80_rtc_proc,
        .read_alarm = m41t80_read_alarm,
        .set_alarm = m41t80_set_alarm,
        .alarm_irq_enable = m41t80_alarm_irq_enable,
};

#ifdef CONFIG_PM_SLEEP
static int m41t80_suspend(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);

        if (client->irq >= 0 && device_may_wakeup(dev))
                enable_irq_wake(client->irq);

        return 0;
}

static int m41t80_resume(struct device *dev)
{
        struct i2c_client *client = to_i2c_client(dev);

        if (client->irq >= 0 && device_may_wakeup(dev))
                disable_irq_wake(client->irq);

        return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(m41t80_pm, m41t80_suspend, m41t80_resume);

#ifdef CONFIG_COMMON_CLK
#define sqw_to_m41t80_data(_hw) container_of(_hw, struct m41t80_data, sqw)

static unsigned long m41t80_decode_freq(int setting)
{
        return (setting == 0) ? 0 : (setting == 1) ? M41T80_SQW_MAX_FREQ :
                M41T80_SQW_MAX_FREQ >> setting;
}

static unsigned long m41t80_get_freq(struct m41t80_data *m41t80)
{
        struct i2c_client *client = m41t80->client;
        int reg_sqw = (m41t80->features & M41T80_FEATURE_SQ_ALT) ?
                M41T80_REG_WDAY : M41T80_REG_SQW;
        int ret = i2c_smbus_read_byte_data(client, reg_sqw);

        if (ret < 0)
                return 0;
        return m41t80_decode_freq(ret >> 4);
}

static unsigned long m41t80_sqw_recalc_rate(struct clk_hw *hw,
                                            unsigned long parent_rate)
{
        return sqw_to_m41t80_data(hw)->freq;
}

static int m41t80_sqw_determine_rate(struct clk_hw *hw,
                                     struct clk_rate_request *req)
{
        if (req->rate >= M41T80_SQW_MAX_FREQ)
                req->rate = M41T80_SQW_MAX_FREQ;
        else if (req->rate >= M41T80_SQW_MAX_FREQ / 4)
                req->rate = M41T80_SQW_MAX_FREQ / 4;
        else if (req->rate)
                req->rate = 1 << ilog2(req->rate);

        return 0;
}

static int m41t80_sqw_set_rate(struct clk_hw *hw, unsigned long rate,
                               unsigned long parent_rate)
{
        struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);
        struct i2c_client *client = m41t80->client;
        int reg_sqw = (m41t80->features & M41T80_FEATURE_SQ_ALT) ?
                M41T80_REG_WDAY : M41T80_REG_SQW;
        int reg, ret, val = 0;

        if (rate >= M41T80_SQW_MAX_FREQ)
                val = 1;
        else if (rate >= M41T80_SQW_MAX_FREQ / 4)
                val = 2;
        else if (rate)
                val = 15 - ilog2(rate);

        reg = i2c_smbus_read_byte_data(client, reg_sqw);
        if (reg < 0)
                return reg;

        reg = (reg & 0x0f) | (val << 4);

        ret = i2c_smbus_write_byte_data(client, reg_sqw, reg);
        if (!ret)
                m41t80->freq = m41t80_decode_freq(val);
        return ret;
}

static int m41t80_sqw_control(struct clk_hw *hw, bool enable)
{
        struct m41t80_data *m41t80 = sqw_to_m41t80_data(hw);
        struct i2c_client *client = m41t80->client;
        int ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);

        if (ret < 0)
                return ret;

        if (enable)
                ret |= M41T80_ALMON_SQWE;
        else
                ret &= ~M41T80_ALMON_SQWE;

        ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON, ret);
        if (!ret)
                m41t80->sqwe = enable;
        return ret;
}

static int m41t80_sqw_prepare(struct clk_hw *hw)
{
        return m41t80_sqw_control(hw, 1);
}

static void m41t80_sqw_unprepare(struct clk_hw *hw)
{
        m41t80_sqw_control(hw, 0);
}

static int m41t80_sqw_is_prepared(struct clk_hw *hw)
{
        return sqw_to_m41t80_data(hw)->sqwe;
}

static const struct clk_ops m41t80_sqw_ops = {
        .prepare = m41t80_sqw_prepare,
        .unprepare = m41t80_sqw_unprepare,
        .is_prepared = m41t80_sqw_is_prepared,
        .recalc_rate = m41t80_sqw_recalc_rate,
        .determine_rate = m41t80_sqw_determine_rate,
        .set_rate = m41t80_sqw_set_rate,
};

static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80)
{
        struct i2c_client *client = m41t80->client;
        struct device_node *node = client->dev.of_node;
        struct device_node *fixed_clock;
        struct clk *clk;
        struct clk_init_data init;
        int ret;

        fixed_clock = of_get_child_by_name(node, "clock");
        if (fixed_clock) {
                /*
                 * skip registering square wave clock when a fixed
                 * clock has been registered. The fixed clock is
                 * registered automatically when being referenced.
                 */
                of_node_put(fixed_clock);
                return NULL;
        }

        /* First disable the clock */
        ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
        if (ret < 0)
                return ERR_PTR(ret);
        ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
                                        ret & ~(M41T80_ALMON_SQWE));
        if (ret < 0)
                return ERR_PTR(ret);

        init.name = "m41t80-sqw";
        init.ops = &m41t80_sqw_ops;
        init.flags = 0;
        init.parent_names = NULL;
        init.num_parents = 0;
        m41t80->sqw.init = &init;
        m41t80->freq = m41t80_get_freq(m41t80);

        /* optional override of the clockname */
        of_property_read_string(node, "clock-output-names", &init.name);

        /* register the clock */
        clk = clk_register(&client->dev, &m41t80->sqw);
        if (!IS_ERR(clk))
                of_clk_add_provider(node, of_clk_src_simple_get, clk);

        return clk;
}
#endif

#ifdef CONFIG_RTC_DRV_M41T80_WDT
/*
 *****************************************************************************
 *
 * Watchdog Driver
 *
 *****************************************************************************
 */
static DEFINE_MUTEX(m41t80_rtc_mutex);
static struct i2c_client *save_client;

/* Default margin */
#define WD_TIMO 60              /* 1..31 seconds */

static int wdt_margin = WD_TIMO;
module_param(wdt_margin, int, 0);
MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 60s)");

static unsigned long wdt_is_open;
static int boot_flag;

/**
 *      wdt_ping - Reload counter one with the watchdog timeout.
 *      We don't bother reloading the cascade counter.
 */
static void wdt_ping(void)
{
        unsigned char i2c_data[2];
        struct i2c_msg msgs1[1] = {
                {
                        .addr   = save_client->addr,
                        .flags  = 0,
                        .len    = 2,
                        .buf    = i2c_data,
                },
        };
        struct m41t80_data *clientdata = i2c_get_clientdata(save_client);

        i2c_data[0] = 0x09;             /* watchdog register */

        if (wdt_margin > 31)
                i2c_data[1] = (wdt_margin & 0xFC) | 0x83; /* resolution = 4s */
        else
                /*
                 * WDS = 1 (0x80), mulitplier = WD_TIMO, resolution = 1s (0x02)
                 */
                i2c_data[1] = wdt_margin << 2 | 0x82;

        /*
         * M41T65 has three bits for watchdog resolution.  Don't set bit 7, as
         * that would be an invalid resolution.
         */
        if (clientdata->features & M41T80_FEATURE_WD)
                i2c_data[1] &= ~M41T80_WATCHDOG_RB2;

        i2c_transfer(save_client->adapter, msgs1, 1);
}

/**
 *      wdt_disable - disables watchdog.
 */
static void wdt_disable(void)
{
        unsigned char i2c_data[2], i2c_buf[0x10];
        struct i2c_msg msgs0[2] = {
                {
                        .addr   = save_client->addr,
                        .flags  = 0,
                        .len    = 1,
                        .buf    = i2c_data,
                },
                {
                        .addr   = save_client->addr,
                        .flags  = I2C_M_RD,
                        .len    = 1,
                        .buf    = i2c_buf,
                },
        };
        struct i2c_msg msgs1[1] = {
                {
                        .addr   = save_client->addr,
                        .flags  = 0,
                        .len    = 2,
                        .buf    = i2c_data,
                },
        };

        i2c_data[0] = 0x09;
        i2c_transfer(save_client->adapter, msgs0, 2);

        i2c_data[0] = 0x09;
        i2c_data[1] = 0x00;
        i2c_transfer(save_client->adapter, msgs1, 1);
}

/**
 *      wdt_write - write to watchdog.
 *      @file: file handle to the watchdog
 *      @buf: buffer to write (unused as data does not matter here
 *      @count: count of bytes
 *      @ppos: pointer to the position to write. No seeks allowed
 *
 *      A write to a watchdog device is defined as a keepalive signal. Any
 *      write of data will do, as we don't define content meaning.
 */
static ssize_t wdt_write(struct file *file, const char __user *buf,
                         size_t count, loff_t *ppos)
{
        if (count) {
                wdt_ping();
                return 1;
        }
        return 0;
}

static ssize_t wdt_read(struct file *file, char __user *buf,
                        size_t count, loff_t *ppos)
{
        return 0;
}

/**
 *      wdt_ioctl - ioctl handler to set watchdog.
 *      @file: file handle to the device
 *      @cmd: watchdog command
 *      @arg: argument pointer
 *
 *      The watchdog API defines a common set of functions for all watchdogs
 *      according to their available features. We only actually usefully support
 *      querying capabilities and current status.
 */
static int wdt_ioctl(struct file *file, unsigned int cmd,
                     unsigned long arg)
{
        int new_margin, rv;
        static struct watchdog_info ident = {
                .options = WDIOF_POWERUNDER | WDIOF_KEEPALIVEPING |
                        WDIOF_SETTIMEOUT,
                .firmware_version = 1,
                .identity = "M41T80 WTD"
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user((struct watchdog_info __user *)arg, &ident,
                                    sizeof(ident)) ? -EFAULT : 0;

        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(boot_flag, (int __user *)arg);
        case WDIOC_KEEPALIVE:
                wdt_ping();
                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(new_margin, (int __user *)arg))
                        return -EFAULT;
                /* Arbitrary, can't find the card's limits */
                if (new_margin < 1 || new_margin > 124)
                        return -EINVAL;
                wdt_margin = new_margin;
                wdt_ping();
                fallthrough;
        case WDIOC_GETTIMEOUT:
                return put_user(wdt_margin, (int __user *)arg);

        case WDIOC_SETOPTIONS:
                if (copy_from_user(&rv, (int __user *)arg, sizeof(int)))
                        return -EFAULT;

                if (rv & WDIOS_DISABLECARD) {
                        pr_info("disable watchdog\n");
                        wdt_disable();
                }

                if (rv & WDIOS_ENABLECARD) {
                        pr_info("enable watchdog\n");
                        wdt_ping();
                }

                return -EINVAL;
        }
        return -ENOTTY;
}

static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
                               unsigned long arg)
{
        int ret;

        mutex_lock(&m41t80_rtc_mutex);
        ret = wdt_ioctl(file, cmd, arg);
        mutex_unlock(&m41t80_rtc_mutex);

        return ret;
}

/**
 *      wdt_open - open a watchdog.
 *      @inode: inode of device
 *      @file: file handle to device
 *
 */
static int wdt_open(struct inode *inode, struct file *file)
{
        if (iminor(inode) == WATCHDOG_MINOR) {
                mutex_lock(&m41t80_rtc_mutex);
                if (test_and_set_bit(0, &wdt_is_open)) {
                        mutex_unlock(&m41t80_rtc_mutex);
                        return -EBUSY;
                }
                /*
                 *      Activate
                 */
                wdt_is_open = 1;
                mutex_unlock(&m41t80_rtc_mutex);
                return stream_open(inode, file);
        }
        return -ENODEV;
}

/**
 *      wdt_release - release a watchdog.
 *      @inode: inode to board
 *      @file: file handle to board
 *
 */
static int wdt_release(struct inode *inode, struct file *file)
{
        if (iminor(inode) == WATCHDOG_MINOR)
                clear_bit(0, &wdt_is_open);
        return 0;
}

/**
 *      wdt_notify_sys - notify to watchdog.
 *      @this: our notifier block
 *      @code: the event being reported
 *      @unused: unused
 *
 *      Our notifier is called on system shutdowns. We want to turn the card
 *      off at reboot otherwise the machine will reboot again during memory
 *      test or worse yet during the following fsck. This would suck, in fact
 *      trust me - if it happens it does suck.
 */
static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
                          void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                /* Disable Watchdog */
                wdt_disable();
        return NOTIFY_DONE;
}

static const struct file_operations wdt_fops = {
        .owner  = THIS_MODULE,
        .read   = wdt_read,
        .unlocked_ioctl = wdt_unlocked_ioctl,
        .compat_ioctl = compat_ptr_ioctl,
        .write  = wdt_write,
        .open   = wdt_open,
        .release = wdt_release,
};

static struct miscdevice wdt_dev = {
        .minor = WATCHDOG_MINOR,
        .name = "watchdog",
        .fops = &wdt_fops,
};

/*
 *      The WDT card needs to learn about soft shutdowns in order to
 *      turn the timebomb registers off.
 */
static struct notifier_block wdt_notifier = {
        .notifier_call = wdt_notify_sys,
};
#endif /* CONFIG_RTC_DRV_M41T80_WDT */

/*
 *****************************************************************************
 *
 *      Driver Interface
 *
 *****************************************************************************
 */

static int m41t80_probe(struct i2c_client *client)
{
        struct i2c_adapter *adapter = client->adapter;
        int rc = 0;
        struct rtc_time tm;
        struct m41t80_data *m41t80_data = NULL;
        bool wakeup_source = false;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_I2C_BLOCK |
                                     I2C_FUNC_SMBUS_BYTE_DATA)) {
                dev_err(&adapter->dev, "doesn't support I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK\n");
                return -ENODEV;
        }

        m41t80_data = devm_kzalloc(&client->dev, sizeof(*m41t80_data),
                                   GFP_KERNEL);
        if (!m41t80_data)
                return -ENOMEM;

        m41t80_data->client = client;
        if (client->dev.of_node) {
                m41t80_data->features = (unsigned long)
                        of_device_get_match_data(&client->dev);
        } else {
                const struct i2c_device_id *id = i2c_match_id(m41t80_id, client);
                m41t80_data->features = id->driver_data;
        }
        i2c_set_clientdata(client, m41t80_data);

        m41t80_data->rtc =  devm_rtc_allocate_device(&client->dev);
        if (IS_ERR(m41t80_data->rtc))
                return PTR_ERR(m41t80_data->rtc);

        wakeup_source = device_property_read_bool(&client->dev, "wakeup-source");
        if (client->irq > 0) {
                unsigned long irqflags = IRQF_TRIGGER_LOW;

                if (dev_fwnode(&client->dev))
                        irqflags = 0;

                rc = devm_request_threaded_irq(&client->dev, client->irq,
                                               NULL, m41t80_handle_irq,
                                               irqflags | IRQF_ONESHOT,
                                               "m41t80", client);
                if (rc) {
                        dev_warn(&client->dev, "unable to request IRQ, alarms disabled\n");
                        client->irq = 0;
                        wakeup_source = false;
                }
        }
        if (client->irq > 0 || wakeup_source)
                device_init_wakeup(&client->dev, true);
        else
                clear_bit(RTC_FEATURE_ALARM, m41t80_data->rtc->features);

        m41t80_data->rtc->ops = &m41t80_rtc_ops;
        m41t80_data->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
        m41t80_data->rtc->range_max = RTC_TIMESTAMP_END_2099;

        if (client->irq <= 0)
                clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, m41t80_data->rtc->features);

        /* Make sure HT (Halt Update) bit is cleared */
        rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);

        if (rc >= 0 && rc & M41T80_ALHOUR_HT) {
                if (m41t80_data->features & M41T80_FEATURE_HT) {
                        m41t80_rtc_read_time(&client->dev, &tm);
                        dev_info(&client->dev, "HT bit was set!\n");
                        dev_info(&client->dev, "Power Down at %ptR\n", &tm);
                }
                rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_HOUR,
                                               rc & ~M41T80_ALHOUR_HT);
        }

        if (rc < 0) {
                dev_err(&client->dev, "Can't clear HT bit\n");
                return rc;
        }

        /* Make sure ST (stop) bit is cleared */
        rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);

        if (rc >= 0 && rc & M41T80_SEC_ST)
                rc = i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
                                               rc & ~M41T80_SEC_ST);
        if (rc < 0) {
                dev_err(&client->dev, "Can't clear ST bit\n");
                return rc;
        }

#ifdef CONFIG_RTC_DRV_M41T80_WDT
        if (m41t80_data->features & M41T80_FEATURE_HT) {
                save_client = client;
                rc = misc_register(&wdt_dev);
                if (rc)
                        return rc;
                rc = register_reboot_notifier(&wdt_notifier);
                if (rc) {
                        misc_deregister(&wdt_dev);
                        return rc;
                }
        }
#endif
#ifdef CONFIG_COMMON_CLK
        if (m41t80_data->features & M41T80_FEATURE_SQ)
                m41t80_sqw_register_clk(m41t80_data);
#endif

        rc = devm_rtc_register_device(m41t80_data->rtc);
        if (rc)
                return rc;

        return 0;
}

static void m41t80_remove(struct i2c_client *client)
{
#ifdef CONFIG_RTC_DRV_M41T80_WDT
        struct m41t80_data *clientdata = i2c_get_clientdata(client);

        if (clientdata->features & M41T80_FEATURE_HT) {
                misc_deregister(&wdt_dev);
                unregister_reboot_notifier(&wdt_notifier);
        }
#endif
}

static struct i2c_driver m41t80_driver = {
        .driver = {
                .name = "rtc-m41t80",
                .of_match_table = of_match_ptr(m41t80_of_match),
                .pm = &m41t80_pm,
        },
        .probe = m41t80_probe,
        .remove = m41t80_remove,
        .id_table = m41t80_id,
};

module_i2c_driver(m41t80_driver);

MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
MODULE_LICENSE("GPL");