// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * RTC driver for the SD2405AL Real-Time Clock
 *
 * Datasheet:
 * https://image.dfrobot.com/image/data/TOY0021/SD2405AL%20datasheet%20(Angelo%20v0.1).pdf
 *
 * I2C slave address: 0x32
 *
 * Copyright (C) 2024-2025 Tóth János <gomba007@gmail.com>
 */

#include <linux/bcd.h>
#include <linux/i2c.h>
#include <linux/regmap.h>
#include <linux/rtc.h>

/* Real time clock registers */
#define SD2405AL_REG_T_SEC      0x00
#define SD2405AL_REG_T_MIN      0x01
#define SD2405AL_REG_T_HOUR     0x02
#       define SD2405AL_BIT_12H_PM      BIT(5)
#       define SD2405AL_BIT_24H         BIT(7)
#define SD2405AL_REG_T_WEEK     0x03
#define SD2405AL_REG_T_DAY      0x04
#define SD2405AL_REG_T_MON      0x05
#define SD2405AL_REG_T_YEAR     0x06

#define SD2405AL_NUM_T_REGS     (SD2405AL_REG_T_YEAR - SD2405AL_REG_T_SEC + 1)

/* Control registers */
#define SD2405AL_REG_CTR1       0x0F
#       define SD2405AL_BIT_WRTC2       BIT(2)
#       define SD2405AL_BIT_WRTC3       BIT(7)
#define SD2405AL_REG_CTR2       0x10
#       define SD2405AL_BIT_WRTC1       BIT(7)
#define SD2405AL_REG_CTR3       0x11
#define SD2405AL_REG_TTF        0x12
#define SD2405AL_REG_CNTDWN     0x13

/* General RAM */
#define SD2405AL_REG_M_START    0x14
#define SD2405AL_REG_M_END      0x1F

struct sd2405al {
        struct device           *dev;
        struct regmap           *regmap;
};

static int sd2405al_enable_reg_write(struct sd2405al *sd2405al)
{
        int ret;

        /* order of writes is important */
        ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR2,
                                 SD2405AL_BIT_WRTC1, SD2405AL_BIT_WRTC1);
        if (ret < 0)
                return ret;

        ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR1,
                                 SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3,
                                 SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3);
        if (ret < 0)
                return ret;

        return 0;
}

static int sd2405al_disable_reg_write(struct sd2405al *sd2405al)
{
        int ret;

        /* order of writes is important */
        ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR1,
                                 SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3, 0x00);
        if (ret < 0)
                return ret;

        ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR2,
                                 SD2405AL_BIT_WRTC1, 0x00);
        if (ret < 0)
                return ret;

        return 0;
}

static int sd2405al_read_time(struct device *dev, struct rtc_time *time)
{
        u8 data[SD2405AL_NUM_T_REGS] = { 0 };
        struct sd2405al *sd2405al = dev_get_drvdata(dev);
        int ret;

        ret = regmap_bulk_read(sd2405al->regmap, SD2405AL_REG_T_SEC, data,
                               SD2405AL_NUM_T_REGS);
        if (ret < 0)
                return ret;

        time->tm_sec = bcd2bin(data[SD2405AL_REG_T_SEC] & 0x7F);
        time->tm_min = bcd2bin(data[SD2405AL_REG_T_MIN] & 0x7F);

        if (data[SD2405AL_REG_T_HOUR] & SD2405AL_BIT_24H)
                time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR] & 0x3F);
        else
                if (data[SD2405AL_REG_T_HOUR] & SD2405AL_BIT_12H_PM)
                        time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR]
                                                & 0x1F) + 12;
                else /* 12 hour mode, AM */
                        time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR]
                                                & 0x1F);

        time->tm_wday = bcd2bin(data[SD2405AL_REG_T_WEEK] & 0x07);
        time->tm_mday = bcd2bin(data[SD2405AL_REG_T_DAY] & 0x3F);
        time->tm_mon = bcd2bin(data[SD2405AL_REG_T_MON] & 0x1F) - 1;
        time->tm_year = bcd2bin(data[SD2405AL_REG_T_YEAR]) + 100;

        dev_dbg(sd2405al->dev, "read time: %ptR (%d)\n", time, time->tm_wday);

        return 0;
}

static int sd2405al_set_time(struct device *dev, struct rtc_time *time)
{
        u8 data[SD2405AL_NUM_T_REGS];
        struct sd2405al *sd2405al = dev_get_drvdata(dev);
        int ret;

        data[SD2405AL_REG_T_SEC] = bin2bcd(time->tm_sec);
        data[SD2405AL_REG_T_MIN] = bin2bcd(time->tm_min);
        data[SD2405AL_REG_T_HOUR] = bin2bcd(time->tm_hour) | SD2405AL_BIT_24H;
        data[SD2405AL_REG_T_DAY] = bin2bcd(time->tm_mday);
        data[SD2405AL_REG_T_WEEK] = bin2bcd(time->tm_wday);
        data[SD2405AL_REG_T_MON] = bin2bcd(time->tm_mon) + 1;
        data[SD2405AL_REG_T_YEAR] = bin2bcd(time->tm_year - 100);

        ret = sd2405al_enable_reg_write(sd2405al);
        if (ret < 0)
                return ret;

        ret = regmap_bulk_write(sd2405al->regmap, SD2405AL_REG_T_SEC, data,
                                SD2405AL_NUM_T_REGS);
        if (ret < 0)
                return ret;

        ret = regmap_write(sd2405al->regmap, SD2405AL_REG_TTF, 0x00);
        if (ret < 0)
                return ret;

        ret = sd2405al_disable_reg_write(sd2405al);
        if (ret < 0)
                return ret;

        dev_dbg(sd2405al->dev, "set time: %ptR (%d)\n", time, time->tm_wday);

        return 0;
}

static const struct rtc_class_ops sd2405al_rtc_ops = {
        .read_time = sd2405al_read_time,
        .set_time = sd2405al_set_time,
};

static const struct regmap_config sd2405al_regmap_conf = {
        .reg_bits = 8,
        .val_bits = 8,
        .max_register = SD2405AL_REG_M_END,
};

static int sd2405al_probe(struct i2c_client *client)
{
        struct sd2405al *sd2405al;
        struct rtc_device *rtc;
        int ret;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                return -ENODEV;

        sd2405al = devm_kzalloc(&client->dev, sizeof(*sd2405al), GFP_KERNEL);
        if (!sd2405al)
                return -ENOMEM;

        sd2405al->dev = &client->dev;

        sd2405al->regmap = devm_regmap_init_i2c(client, &sd2405al_regmap_conf);
        if (IS_ERR(sd2405al->regmap))
                return PTR_ERR(sd2405al->regmap);

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

        rtc->ops = &sd2405al_rtc_ops;
        rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
        rtc->range_max = RTC_TIMESTAMP_END_2099;

        dev_set_drvdata(&client->dev, sd2405al);

        ret = devm_rtc_register_device(rtc);
        if (ret < 0)
                return ret;

        return 0;
}

static const struct i2c_device_id sd2405al_id[] = {
        { "sd2405al" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(i2c, sd2405al_id);

static const __maybe_unused struct of_device_id sd2405al_of_match[] = {
        { .compatible = "dfrobot,sd2405al" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, sd2405al_of_match);

static struct i2c_driver sd2405al_driver = {
        .driver = {
                .name = "sd2405al",
                .of_match_table = of_match_ptr(sd2405al_of_match),
        },
        .probe = sd2405al_probe,
        .id_table = sd2405al_id,
};

module_i2c_driver(sd2405al_driver);

MODULE_AUTHOR("Tóth János <gomba007@gmail.com>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("SD2405AL RTC driver");