// SPDX-License-Identifier: GPL-2.0-only
/* rtc-ds1347.c
 *
 * Driver for Dallas Semiconductor DS1347 Low Current, SPI Compatible
 * Real Time Clock
 *
 * Author : Raghavendra Chandra Ganiga <ravi23ganiga@gmail.com>
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>
#include <linux/regmap.h>

/* Registers in ds1347 rtc */

#define DS1347_SECONDS_REG      0x01
#define DS1347_MINUTES_REG      0x03
#define DS1347_HOURS_REG        0x05
#define DS1347_DATE_REG         0x07
#define DS1347_MONTH_REG        0x09
#define DS1347_DAY_REG          0x0B
#define DS1347_YEAR_REG         0x0D
#define DS1347_CONTROL_REG      0x0F
#define DS1347_CENTURY_REG      0x13
#define DS1347_STATUS_REG       0x17
#define DS1347_CLOCK_BURST      0x3F

#define DS1347_WP_BIT           BIT(7)

#define DS1347_NEOSC_BIT        BIT(7)
#define DS1347_OSF_BIT          BIT(2)

static const struct regmap_range ds1347_ranges[] = {
        {
                .range_min = DS1347_SECONDS_REG,
                .range_max = DS1347_STATUS_REG,
        },
};

static const struct regmap_access_table ds1347_access_table = {
        .yes_ranges = ds1347_ranges,
        .n_yes_ranges = ARRAY_SIZE(ds1347_ranges),
};

static int ds1347_read_time(struct device *dev, struct rtc_time *dt)
{
        struct regmap *map = dev_get_drvdata(dev);
        unsigned int status, century, secs;
        unsigned char buf[8];
        int err;

        err = regmap_read(map, DS1347_STATUS_REG, &status);
        if (err)
                return err;

        if (status & DS1347_OSF_BIT)
                return -EINVAL;

        do {
                err = regmap_bulk_read(map, DS1347_CLOCK_BURST, buf, 8);
                if (err)
                        return err;

                err = regmap_read(map, DS1347_CENTURY_REG, &century);
                if (err)
                        return err;

                err = regmap_read(map, DS1347_SECONDS_REG, &secs);
                if (err)
                        return err;
        } while (buf[0] != secs);

        dt->tm_sec = bcd2bin(buf[0]);
        dt->tm_min = bcd2bin(buf[1] & 0x7f);
        dt->tm_hour = bcd2bin(buf[2] & 0x3F);
        dt->tm_mday = bcd2bin(buf[3]);
        dt->tm_mon = bcd2bin(buf[4]) - 1;
        dt->tm_wday = bcd2bin(buf[5]) - 1;
        dt->tm_year = (bcd2bin(century) * 100) + bcd2bin(buf[6]) - 1900;

        return 0;
}

static int ds1347_set_time(struct device *dev, struct rtc_time *dt)
{
        struct regmap *map = dev_get_drvdata(dev);
        unsigned int century;
        unsigned char buf[8];
        int err;

        err = regmap_update_bits(map, DS1347_STATUS_REG,
                                 DS1347_NEOSC_BIT, DS1347_NEOSC_BIT);
        if (err)
                return err;

        buf[0] = bin2bcd(dt->tm_sec);
        buf[1] = bin2bcd(dt->tm_min);
        buf[2] = (bin2bcd(dt->tm_hour) & 0x3F);
        buf[3] = bin2bcd(dt->tm_mday);
        buf[4] = bin2bcd(dt->tm_mon + 1);
        buf[5] = bin2bcd(dt->tm_wday + 1);
        buf[6] = bin2bcd(dt->tm_year % 100);
        buf[7] = bin2bcd(0x00);

        err = regmap_bulk_write(map, DS1347_CLOCK_BURST, buf, 8);
        if (err)
                return err;

        century = (dt->tm_year / 100) + 19;
        err = regmap_write(map, DS1347_CENTURY_REG, bin2bcd(century));
        if (err)
                return err;

        return regmap_update_bits(map, DS1347_STATUS_REG,
                                  DS1347_NEOSC_BIT | DS1347_OSF_BIT, 0);
}

static const struct rtc_class_ops ds1347_rtc_ops = {
        .read_time = ds1347_read_time,
        .set_time = ds1347_set_time,
};

static int ds1347_probe(struct spi_device *spi)
{
        struct rtc_device *rtc;
        struct regmap_config config;
        struct regmap *map;
        int err;

        memset(&config, 0, sizeof(config));
        config.reg_bits = 8;
        config.val_bits = 8;
        config.read_flag_mask = 0x80;
        config.max_register = 0x3F;
        config.wr_table = &ds1347_access_table;

        /* spi setup with ds1347 in mode 3 and bits per word as 8 */
        spi->mode = SPI_MODE_3;
        spi->bits_per_word = 8;
        spi_setup(spi);

        map = devm_regmap_init_spi(spi, &config);

        if (IS_ERR(map)) {
                dev_err(&spi->dev, "ds1347 regmap init spi failed\n");
                return PTR_ERR(map);
        }

        spi_set_drvdata(spi, map);

        /* Disable the write protect of rtc */
        err = regmap_update_bits(map, DS1347_CONTROL_REG, DS1347_WP_BIT, 0);
        if (err)
                return err;

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

        rtc->ops = &ds1347_rtc_ops;
        rtc->range_min = RTC_TIMESTAMP_BEGIN_0000;
        rtc->range_max = RTC_TIMESTAMP_END_9999;

        return devm_rtc_register_device(rtc);
}

static struct spi_driver ds1347_driver = {
        .driver = {
                .name = "ds1347",
        },
        .probe = ds1347_probe,
};

module_spi_driver(ds1347_driver);

MODULE_DESCRIPTION("DS1347 SPI RTC DRIVER");
MODULE_AUTHOR("Raghavendra C Ganiga <ravi23ganiga@gmail.com>");
MODULE_LICENSE("GPL v2");