// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for Epson RX8111 RTC.
 *
 * Copyright (C) 2023 Axis Communications AB
 */

#include <linux/bcd.h>
#include <linux/bitfield.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/regmap.h>

#include <linux/rtc.h>

#define RX8111_REG_SEC                  0x10    /* Second counter. */
#define RX8111_REG_MIN                  0x11    /* Minute counter */
#define RX8111_REG_HOUR                 0x12    /* Hour counter. */
#define RX8111_REG_WEEK                 0x13    /* Week day counter. */
#define RX8111_REG_DAY                  0x14    /* Month day counter. */
#define RX8111_REG_MONTH                0x15    /* Month counter. */
#define RX8111_REG_YEAR                 0x16    /* Year counter. */

#define RX8111_REG_ALARM_MIN            0x17    /* Alarm minute. */
#define RX8111_REG_ALARM_HOUR           0x18    /* Alarm hour. */
#define RX8111_REG_ALARM_WEEK_DAY       0x19    /* Alarm week or month day. */

#define RX8111_REG_TIMER_COUNTER0       0x1a    /* Timer counter LSB. */
#define RX8111_REG_TIMER_COUNTER1       0x1b    /* Timer counter. */
#define RX8111_REG_TIMER_COUNTER2       0x1c    /* Timer counter MSB. */

#define RX8111_REG_EXT                  0x1d    /* Extension register. */
#define RX8111_REG_FLAG                 0x1e    /* Flag register. */
#define RX8111_REG_CTRL                 0x1f    /* Control register. */

#define RX8111_REG_TS_1_1000_SEC        0x20    /* Timestamp 256 or 512 Hz . */
#define RX8111_REG_TS_1_100_SEC         0x21    /* Timestamp 1 - 128 Hz. */
#define RX8111_REG_TS_SEC               0x22    /* Timestamp second. */
#define RX8111_REG_TS_MIN               0x23    /* Timestamp minute. */
#define RX8111_REG_TS_HOUR              0x24    /* Timestamp hour. */
#define RX8111_REG_TS_WEEK              0x25    /* Timestamp week day. */
#define RX8111_REG_TS_DAY               0x26    /* Timestamp month day. */
#define RX8111_REG_TS_MONTH             0x27    /* Timestamp month. */
#define RX8111_REG_TS_YEAR              0x28    /* Timestamp year. */
#define RX8111_REG_TS_STATUS            0x29    /* Timestamp status. */

#define RX8111_REG_EVIN_SETTING         0x2b    /* Timestamp trigger setting. */
#define RX8111_REG_ALARM_SEC            0x2c    /* Alarm second. */
#define RX8111_REG_TIMER_CTRL           0x2d    /* Timer control. */
#define RX8111_REG_TS_CTRL0             0x2e    /* Timestamp control 0. */
#define RX8111_REG_CMD_TRIGGER          0x2f    /* Timestamp trigger. */
#define RX8111_REG_PWR_SWITCH_CTRL      0x32    /* Power switch control. */
#define RX8111_REG_STATUS_MON           0x33    /* Status monitor. */
#define RX8111_REG_TS_CTRL1             0x34    /* Timestamp control 1. */
#define RX8111_REG_TS_CTRL2             0x35    /* Timestamp control 2. */
#define RX8111_REG_TS_CTRL3             0x36    /* Timestamp control 3. */

#define RX8111_FLAG_XST_BIT BIT(0)
#define RX8111_FLAG_VLF_BIT BIT(1)

#define RX8111_TIME_BUF_SZ (RX8111_REG_YEAR - RX8111_REG_SEC + 1)

enum rx8111_regfield {
        /* RX8111_REG_EXT. */
        RX8111_REGF_TSEL0,
        RX8111_REGF_TSEL1,
        RX8111_REGF_ETS,
        RX8111_REGF_WADA,
        RX8111_REGF_TE,
        RX8111_REGF_USEL,
        RX8111_REGF_FSEL0,
        RX8111_REGF_FSEL1,

        /* RX8111_REG_FLAG. */
        RX8111_REGF_XST,
        RX8111_REGF_VLF,
        RX8111_REGF_EVF,
        RX8111_REGF_AF,
        RX8111_REGF_TF,
        RX8111_REGF_UF,
        RX8111_REGF_POR,

        /* RX8111_REG_CTRL. */
        RX8111_REGF_STOP,
        RX8111_REGF_EIE,
        RX8111_REGF_AIE,
        RX8111_REGF_TIE,
        RX8111_REGF_UIE,

        /* RX8111_REG_PWR_SWITCH_CTRL. */
        RX8111_REGF_SMPT0,
        RX8111_REGF_SMPT1,
        RX8111_REGF_SWSEL0,
        RX8111_REGF_SWSEL1,
        RX8111_REGF_INIEN,
        RX8111_REGF_CHGEN,

        /* RX8111_REG_STATUS_MON. */
        RX8111_REGF_VLOW,

        /* Sentinel value. */
        RX8111_REGF_MAX
};

static const struct reg_field rx8111_regfields[] = {
        [RX8111_REGF_TSEL0] = REG_FIELD(RX8111_REG_EXT, 0, 0),
        [RX8111_REGF_TSEL1] = REG_FIELD(RX8111_REG_EXT, 1, 1),
        [RX8111_REGF_ETS]   = REG_FIELD(RX8111_REG_EXT, 2, 2),
        [RX8111_REGF_WADA]  = REG_FIELD(RX8111_REG_EXT, 3, 3),
        [RX8111_REGF_TE]    = REG_FIELD(RX8111_REG_EXT, 4, 4),
        [RX8111_REGF_USEL]  = REG_FIELD(RX8111_REG_EXT, 5, 5),
        [RX8111_REGF_FSEL0] = REG_FIELD(RX8111_REG_EXT, 6, 6),
        [RX8111_REGF_FSEL1] = REG_FIELD(RX8111_REG_EXT, 7, 7),

        [RX8111_REGF_XST] = REG_FIELD(RX8111_REG_FLAG, 0, 0),
        [RX8111_REGF_VLF] = REG_FIELD(RX8111_REG_FLAG, 1, 1),
        [RX8111_REGF_EVF] = REG_FIELD(RX8111_REG_FLAG, 2, 2),
        [RX8111_REGF_AF]  = REG_FIELD(RX8111_REG_FLAG, 3, 3),
        [RX8111_REGF_TF]  = REG_FIELD(RX8111_REG_FLAG, 4, 4),
        [RX8111_REGF_UF]  = REG_FIELD(RX8111_REG_FLAG, 5, 5),
        [RX8111_REGF_POR] = REG_FIELD(RX8111_REG_FLAG, 7, 7),

        [RX8111_REGF_STOP] = REG_FIELD(RX8111_REG_CTRL, 0, 0),
        [RX8111_REGF_EIE]  = REG_FIELD(RX8111_REG_CTRL, 2, 2),
        [RX8111_REGF_AIE]  = REG_FIELD(RX8111_REG_CTRL, 3, 3),
        [RX8111_REGF_TIE]  = REG_FIELD(RX8111_REG_CTRL, 4, 4),
        [RX8111_REGF_UIE]  = REG_FIELD(RX8111_REG_CTRL, 5, 5),

        [RX8111_REGF_SMPT0]  = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 0, 0),
        [RX8111_REGF_SMPT1]  = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 1, 1),
        [RX8111_REGF_SWSEL0] = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 2, 2),
        [RX8111_REGF_SWSEL1] = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 3, 3),
        [RX8111_REGF_INIEN]  = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 6, 6),
        [RX8111_REGF_CHGEN]  = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 7, 7),

        [RX8111_REGF_VLOW]  = REG_FIELD(RX8111_REG_STATUS_MON, 1, 1),
};

static const struct regmap_config rx8111_regmap_config = {
        .reg_bits = 8,
        .val_bits = 8,
        .max_register = RX8111_REG_TS_CTRL3,
};

struct rx8111_data {
        struct regmap *regmap;
        struct regmap_field *regfields[RX8111_REGF_MAX];
        struct device *dev;
        struct rtc_device *rtc;
};

static int rx8111_read_vl_flag(struct rx8111_data *data, unsigned int *vlval)
{
        int ret;

        ret = regmap_field_read(data->regfields[RX8111_REGF_VLF], vlval);
        if (ret)
                dev_dbg(data->dev, "Could not read VL flag (%d)", ret);

        return ret;
}

static int rx8111_read_time(struct device *dev, struct rtc_time *tm)
{
        struct rx8111_data *data = dev_get_drvdata(dev);
        u8 buf[RX8111_TIME_BUF_SZ];
        unsigned int regval;
        int ret;

        /* Check status. */
        ret = regmap_read(data->regmap, RX8111_REG_FLAG, &regval);
        if (ret) {
                dev_dbg(data->dev, "Could not read flag register (%d)\n", ret);
                return ret;
        }

        if (FIELD_GET(RX8111_FLAG_XST_BIT, regval)) {
                dev_dbg(data->dev,
                        "Crystal oscillation stopped, time is not reliable\n");
                return -EINVAL;
        }

        if (FIELD_GET(RX8111_FLAG_VLF_BIT, regval)) {
                dev_dbg(data->dev,
                        "Low voltage detected, time is not reliable\n");
                return -EINVAL;
        }

        ret = regmap_field_read(data->regfields[RX8111_REGF_STOP], &regval);
        if (ret) {
                dev_dbg(data->dev, "Could not read clock status (%d)\n", ret);
                return ret;
        }

        if (regval) {
                dev_dbg(data->dev, "Clock stopped, time is not reliable\n");
                return -EINVAL;
        }

        /* Read time. */
        ret = regmap_bulk_read(data->regmap, RX8111_REG_SEC, buf,
                               ARRAY_SIZE(buf));
        if (ret) {
                dev_dbg(data->dev, "Could not bulk read time (%d)\n", ret);
                return ret;
        }

        tm->tm_sec = bcd2bin(buf[0]);
        tm->tm_min = bcd2bin(buf[1]);
        tm->tm_hour = bcd2bin(buf[2]);
        tm->tm_wday = ffs(buf[3]) - 1;
        tm->tm_mday = bcd2bin(buf[4]);
        tm->tm_mon = bcd2bin(buf[5]) - 1;
        tm->tm_year = bcd2bin(buf[6]) + 100;

        return 0;
}

static int rx8111_set_time(struct device *dev, struct rtc_time *tm)
{
        struct rx8111_data *data = dev_get_drvdata(dev);
        u8 buf[RX8111_TIME_BUF_SZ];
        int ret;

        buf[0] = bin2bcd(tm->tm_sec);
        buf[1] = bin2bcd(tm->tm_min);
        buf[2] = bin2bcd(tm->tm_hour);
        buf[3] = BIT(tm->tm_wday);
        buf[4] = bin2bcd(tm->tm_mday);
        buf[5] = bin2bcd(tm->tm_mon + 1);
        buf[6] = bin2bcd(tm->tm_year - 100);

        ret = regmap_clear_bits(data->regmap, RX8111_REG_FLAG,
                                RX8111_FLAG_XST_BIT | RX8111_FLAG_VLF_BIT);
        if (ret)
                return ret;

        /* Stop the clock. */
        ret = regmap_field_write(data->regfields[RX8111_REGF_STOP], 1);
        if (ret) {
                dev_dbg(data->dev, "Could not stop the clock (%d)\n", ret);
                return ret;
        }

        /* Set the time. */
        ret = regmap_bulk_write(data->regmap, RX8111_REG_SEC, buf,
                                ARRAY_SIZE(buf));
        if (ret) {
                dev_dbg(data->dev, "Could not bulk write time (%d)\n", ret);

                /*
                 * We don't bother with trying to start the clock again. We
                 * check for this in rx8111_read_time() (and thus force user to
                 * call rx8111_set_time() to try again).
                 */
                return ret;
        }

        /* Start the clock. */
        ret = regmap_field_write(data->regfields[RX8111_REGF_STOP], 0);
        if (ret) {
                dev_dbg(data->dev, "Could not start the clock (%d)\n", ret);
                return ret;
        }

        return 0;
}

static int rx8111_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
        struct rx8111_data *data = dev_get_drvdata(dev);
        unsigned int regval;
        unsigned int vlval;
        int ret;

        switch (cmd) {
        case RTC_VL_READ:
                ret = rx8111_read_vl_flag(data, &regval);
                if (ret)
                        return ret;

                vlval = regval ? RTC_VL_DATA_INVALID : 0;

                ret = regmap_field_read(data->regfields[RX8111_REGF_VLOW],
                                        &regval);
                if (ret)
                        return ret;

                vlval |= regval ? RTC_VL_BACKUP_LOW : 0;

                return put_user(vlval, (typeof(vlval) __user *)arg);
        default:
                return -ENOIOCTLCMD;
        }
}

static const struct rtc_class_ops rx8111_rtc_ops = {
        .read_time = rx8111_read_time,
        .set_time = rx8111_set_time,
        .ioctl = rx8111_ioctl,
};

static int rx8111_probe(struct i2c_client *client)
{
        struct rx8111_data *data;
        struct rtc_device *rtc;
        size_t i;

        data = devm_kmalloc(&client->dev, sizeof(*data), GFP_KERNEL);
        if (!data) {
                dev_dbg(&client->dev, "Could not allocate device data\n");
                return -ENOMEM;
        }

        data->dev = &client->dev;
        dev_set_drvdata(data->dev, data);

        data->regmap = devm_regmap_init_i2c(client, &rx8111_regmap_config);
        if (IS_ERR(data->regmap)) {
                dev_dbg(data->dev, "Could not initialize regmap\n");
                return PTR_ERR(data->regmap);
        }

        for (i = 0; i < RX8111_REGF_MAX; ++i) {
                data->regfields[i] = devm_regmap_field_alloc(
                        data->dev, data->regmap, rx8111_regfields[i]);
                if (IS_ERR(data->regfields[i])) {
                        dev_dbg(data->dev,
                                "Could not allocate register field %zu\n", i);
                        return PTR_ERR(data->regfields[i]);
                }
        }

        rtc = devm_rtc_allocate_device(data->dev);
        if (IS_ERR(rtc)) {
                dev_dbg(data->dev, "Could not allocate rtc device\n");
                return PTR_ERR(rtc);
        }

        rtc->ops = &rx8111_rtc_ops;
        rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
        rtc->range_max = RTC_TIMESTAMP_END_2099;

        clear_bit(RTC_FEATURE_ALARM, rtc->features);

        return devm_rtc_register_device(rtc);
}

static const struct of_device_id rx8111_of_match[] = {
        {
                .compatible = "epson,rx8111",
        },
        {}
};
MODULE_DEVICE_TABLE(of, rx8111_of_match);

static struct i2c_driver rx8111_driver = {
        .driver = {
                .name = "rtc-rx8111",
                .of_match_table = rx8111_of_match,
        },
        .probe = rx8111_probe,
};
module_i2c_driver(rx8111_driver);

MODULE_AUTHOR("Waqar Hameed <waqar.hameed@axis.com>");
MODULE_DESCRIPTION("Epson RX8111 RTC driver");
MODULE_LICENSE("GPL");