// 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
 *
 * Copyright (C) 2024 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");