// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for the Epson RTC module RX-6110 SA
 *
 * Copyright(C) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
 * Copyright(C) SEIKO EPSON CORPORATION 2013. All rights reserved.
 */

#include <linux/bcd.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/regmap.h>
#include <linux/rtc.h>
#include <linux/of.h>
#include <linux/spi/spi.h>
#include <linux/i2c.h>

/* RX-6110 Register definitions */
#define RX6110_REG_SEC          0x10
#define RX6110_REG_MIN          0x11
#define RX6110_REG_HOUR         0x12
#define RX6110_REG_WDAY         0x13
#define RX6110_REG_MDAY         0x14
#define RX6110_REG_MONTH        0x15
#define RX6110_REG_YEAR         0x16
#define RX6110_REG_RES1         0x17
#define RX6110_REG_ALMIN        0x18
#define RX6110_REG_ALHOUR       0x19
#define RX6110_REG_ALWDAY       0x1A
#define RX6110_REG_TCOUNT0      0x1B
#define RX6110_REG_TCOUNT1      0x1C
#define RX6110_REG_EXT          0x1D
#define RX6110_REG_FLAG         0x1E
#define RX6110_REG_CTRL         0x1F
#define RX6110_REG_USER0        0x20
#define RX6110_REG_USER1        0x21
#define RX6110_REG_USER2        0x22
#define RX6110_REG_USER3        0x23
#define RX6110_REG_USER4        0x24
#define RX6110_REG_USER5        0x25
#define RX6110_REG_USER6        0x26
#define RX6110_REG_USER7        0x27
#define RX6110_REG_USER8        0x28
#define RX6110_REG_USER9        0x29
#define RX6110_REG_USERA        0x2A
#define RX6110_REG_USERB        0x2B
#define RX6110_REG_USERC        0x2C
#define RX6110_REG_USERD        0x2D
#define RX6110_REG_USERE        0x2E
#define RX6110_REG_USERF        0x2F
#define RX6110_REG_RES2         0x30
#define RX6110_REG_RES3         0x31
#define RX6110_REG_IRQ          0x32

#define RX6110_BIT_ALARM_EN             BIT(7)

/* Extension Register (1Dh) bit positions */
#define RX6110_BIT_EXT_TSEL0            BIT(0)
#define RX6110_BIT_EXT_TSEL1            BIT(1)
#define RX6110_BIT_EXT_TSEL2            BIT(2)
#define RX6110_BIT_EXT_WADA             BIT(3)
#define RX6110_BIT_EXT_TE               BIT(4)
#define RX6110_BIT_EXT_USEL             BIT(5)
#define RX6110_BIT_EXT_FSEL0            BIT(6)
#define RX6110_BIT_EXT_FSEL1            BIT(7)

/* Flag Register (1Eh) bit positions */
#define RX6110_BIT_FLAG_VLF             BIT(1)
#define RX6110_BIT_FLAG_AF              BIT(3)
#define RX6110_BIT_FLAG_TF              BIT(4)
#define RX6110_BIT_FLAG_UF              BIT(5)

/* Control Register (1Fh) bit positions */
#define RX6110_BIT_CTRL_TBKE            BIT(0)
#define RX6110_BIT_CTRL_TBKON           BIT(1)
#define RX6110_BIT_CTRL_TSTP            BIT(2)
#define RX6110_BIT_CTRL_AIE             BIT(3)
#define RX6110_BIT_CTRL_TIE             BIT(4)
#define RX6110_BIT_CTRL_UIE             BIT(5)
#define RX6110_BIT_CTRL_STOP            BIT(6)
#define RX6110_BIT_CTRL_TEST            BIT(7)

enum {
        RTC_SEC = 0,
        RTC_MIN,
        RTC_HOUR,
        RTC_WDAY,
        RTC_MDAY,
        RTC_MONTH,
        RTC_YEAR,
        RTC_NR_TIME
};

#define RX6110_DRIVER_NAME              "rx6110"

struct rx6110_data {
        struct rtc_device *rtc;
        struct regmap *regmap;
};

/**
 * rx6110_rtc_tm_to_data - convert rtc_time to native time encoding
 *
 * @tm: holds date and time
 * @data: holds the encoding in rx6110 native form
 */
static int rx6110_rtc_tm_to_data(struct rtc_time *tm, u8 *data)
{
        pr_debug("%s: date %ptRr\n", __func__, tm);

        /*
         * The year in the RTC is a value between 0 and 99.
         * Assume that this represents the current century
         * and disregard all other values.
         */
        if (tm->tm_year < 100 || tm->tm_year >= 200)
                return -EINVAL;

        data[RTC_SEC] = bin2bcd(tm->tm_sec);
        data[RTC_MIN] = bin2bcd(tm->tm_min);
        data[RTC_HOUR] = bin2bcd(tm->tm_hour);
        data[RTC_WDAY] = BIT(bin2bcd(tm->tm_wday));
        data[RTC_MDAY] = bin2bcd(tm->tm_mday);
        data[RTC_MONTH] = bin2bcd(tm->tm_mon + 1);
        data[RTC_YEAR] = bin2bcd(tm->tm_year % 100);

        return 0;
}

/**
 * rx6110_data_to_rtc_tm - convert native time encoding to rtc_time
 *
 * @data: holds the encoding in rx6110 native form
 * @tm: holds date and time
 */
static int rx6110_data_to_rtc_tm(u8 *data, struct rtc_time *tm)
{
        tm->tm_sec = bcd2bin(data[RTC_SEC] & 0x7f);
        tm->tm_min = bcd2bin(data[RTC_MIN] & 0x7f);
        /* only 24-hour clock */
        tm->tm_hour = bcd2bin(data[RTC_HOUR] & 0x3f);
        tm->tm_wday = ffs(data[RTC_WDAY] & 0x7f);
        tm->tm_mday = bcd2bin(data[RTC_MDAY] & 0x3f);
        tm->tm_mon = bcd2bin(data[RTC_MONTH] & 0x1f) - 1;
        tm->tm_year = bcd2bin(data[RTC_YEAR]) + 100;

        pr_debug("%s: date %ptRr\n", __func__, tm);

        /*
         * The year in the RTC is a value between 0 and 99.
         * Assume that this represents the current century
         * and disregard all other values.
         */
        if (tm->tm_year < 100 || tm->tm_year >= 200)
                return -EINVAL;

        return 0;
}

/**
 * rx6110_set_time - set the current time in the rx6110 registers
 *
 * @dev: the rtc device in use
 * @tm: holds date and time
 *
 * BUG: The HW assumes every year that is a multiple of 4 to be a leap
 * year. Next time this is wrong is 2100, which will not be a leap year
 *
 * Note: If STOP is not set/cleared, the clock will start when the seconds
 *       register is written
 *
 */
static int rx6110_set_time(struct device *dev, struct rtc_time *tm)
{
        struct rx6110_data *rx6110 = dev_get_drvdata(dev);
        u8 data[RTC_NR_TIME];
        int ret;

        ret = rx6110_rtc_tm_to_data(tm, data);
        if (ret < 0)
                return ret;

        /* set STOP bit before changing clock/calendar */
        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
                                 RX6110_BIT_CTRL_STOP, RX6110_BIT_CTRL_STOP);
        if (ret)
                return ret;

        ret = regmap_bulk_write(rx6110->regmap, RX6110_REG_SEC, data,
                                RTC_NR_TIME);
        if (ret)
                return ret;

        /* The time in the RTC is valid. Be sure to have VLF cleared. */
        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
                                 RX6110_BIT_FLAG_VLF, 0);
        if (ret)
                return ret;

        /* clear STOP bit after changing clock/calendar */
        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
                                 RX6110_BIT_CTRL_STOP, 0);

        return ret;
}

/**
 * rx6110_get_time - get the current time from the rx6110 registers
 * @dev: the rtc device in use
 * @tm: holds date and time
 */
static int rx6110_get_time(struct device *dev, struct rtc_time *tm)
{
        struct rx6110_data *rx6110 = dev_get_drvdata(dev);
        u8 data[RTC_NR_TIME];
        int flags;
        int ret;

        ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
        if (ret)
                return -EINVAL;

        /* check for VLF Flag (set at power-on) */
        if ((flags & RX6110_BIT_FLAG_VLF)) {
                dev_warn(dev, "Voltage low, data is invalid.\n");
                return -EINVAL;
        }

        /* read registers to date */
        ret = regmap_bulk_read(rx6110->regmap, RX6110_REG_SEC, data,
                               RTC_NR_TIME);
        if (ret)
                return ret;

        ret = rx6110_data_to_rtc_tm(data, tm);
        if (ret)
                return ret;

        dev_dbg(dev, "%s: date %ptRr\n", __func__, tm);

        return 0;
}

static const struct reg_sequence rx6110_default_regs[] = {
        { RX6110_REG_RES1,   0xB8 },
        { RX6110_REG_RES2,   0x00 },
        { RX6110_REG_RES3,   0x10 },
        { RX6110_REG_IRQ,    0x00 },
        { RX6110_REG_ALMIN,  0x00 },
        { RX6110_REG_ALHOUR, 0x00 },
        { RX6110_REG_ALWDAY, 0x00 },
};

/**
 * rx6110_init - initialize the rx6110 registers
 *
 * @rx6110: pointer to the rx6110 struct in use
 *
 */
static int rx6110_init(struct rx6110_data *rx6110)
{
        struct rtc_device *rtc = rx6110->rtc;
        int flags;
        int ret;

        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_EXT,
                                 RX6110_BIT_EXT_TE, 0);
        if (ret)
                return ret;

        ret = regmap_register_patch(rx6110->regmap, rx6110_default_regs,
                                    ARRAY_SIZE(rx6110_default_regs));
        if (ret)
                return ret;

        ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
        if (ret)
                return ret;

        /* check for VLF Flag (set at power-on) */
        if ((flags & RX6110_BIT_FLAG_VLF))
                dev_warn(&rtc->dev, "Voltage low, data loss detected.\n");

        /* check for Alarm Flag */
        if (flags & RX6110_BIT_FLAG_AF)
                dev_warn(&rtc->dev, "An alarm may have been missed.\n");

        /* check for Periodic Timer Flag */
        if (flags & RX6110_BIT_FLAG_TF)
                dev_warn(&rtc->dev, "Periodic timer was detected\n");

        /* check for Update Timer Flag */
        if (flags & RX6110_BIT_FLAG_UF)
                dev_warn(&rtc->dev, "Update timer was detected\n");

        /* clear all flags BUT VLF */
        ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
                                 RX6110_BIT_FLAG_AF |
                                 RX6110_BIT_FLAG_UF |
                                 RX6110_BIT_FLAG_TF,
                                 0);

        return ret;
}

static const struct rtc_class_ops rx6110_rtc_ops = {
        .read_time = rx6110_get_time,
        .set_time = rx6110_set_time,
};

static int rx6110_probe(struct rx6110_data *rx6110, struct device *dev)
{
        int err;

        rx6110->rtc = devm_rtc_device_register(dev,
                                               RX6110_DRIVER_NAME,
                                               &rx6110_rtc_ops, THIS_MODULE);

        if (IS_ERR(rx6110->rtc))
                return PTR_ERR(rx6110->rtc);

        err = rx6110_init(rx6110);
        if (err)
                return err;

        return 0;
}

#if IS_ENABLED(CONFIG_SPI_MASTER)
static const struct regmap_config regmap_spi_config = {
        .reg_bits = 8,
        .val_bits = 8,
        .max_register = RX6110_REG_IRQ,
        .read_flag_mask = 0x80,
};

/**
 * rx6110_spi_probe - initialize rtc driver
 * @spi: pointer to spi device
 */
static int rx6110_spi_probe(struct spi_device *spi)
{
        struct rx6110_data *rx6110;

        if ((spi->bits_per_word && spi->bits_per_word != 8) ||
            (spi->max_speed_hz > 2000000) ||
            (spi->mode != (SPI_CS_HIGH | SPI_CPOL | SPI_CPHA))) {
                dev_warn(&spi->dev, "SPI settings: bits_per_word: %d, max_speed_hz: %d, mode: %xh\n",
                         spi->bits_per_word, spi->max_speed_hz, spi->mode);
                dev_warn(&spi->dev, "driving device in an unsupported mode");
        }

        rx6110 = devm_kzalloc(&spi->dev, sizeof(*rx6110), GFP_KERNEL);
        if (!rx6110)
                return -ENOMEM;

        rx6110->regmap = devm_regmap_init_spi(spi, &regmap_spi_config);
        if (IS_ERR(rx6110->regmap)) {
                dev_err(&spi->dev, "regmap init failed for rtc rx6110\n");
                return PTR_ERR(rx6110->regmap);
        }

        spi_set_drvdata(spi, rx6110);

        return rx6110_probe(rx6110, &spi->dev);
}

static const struct spi_device_id rx6110_spi_id[] = {
        { "rx6110", 0 },
        { }
};
MODULE_DEVICE_TABLE(spi, rx6110_spi_id);

static const __maybe_unused struct of_device_id rx6110_spi_of_match[] = {
        { .compatible = "epson,rx6110" },
        { },
};
MODULE_DEVICE_TABLE(of, rx6110_spi_of_match);

static struct spi_driver rx6110_spi_driver = {
        .driver = {
                .name = RX6110_DRIVER_NAME,
                .of_match_table = of_match_ptr(rx6110_spi_of_match),
        },
        .probe          = rx6110_spi_probe,
        .id_table       = rx6110_spi_id,
};

static int rx6110_spi_register(void)
{
        return spi_register_driver(&rx6110_spi_driver);
}

static void rx6110_spi_unregister(void)
{
        spi_unregister_driver(&rx6110_spi_driver);
}
#else
static int rx6110_spi_register(void)
{
        return 0;
}

static void rx6110_spi_unregister(void)
{
}
#endif /* CONFIG_SPI_MASTER */

#if IS_ENABLED(CONFIG_I2C)
static const struct regmap_config regmap_i2c_config = {
        .reg_bits = 8,
        .val_bits = 8,
        .max_register = RX6110_REG_IRQ,
        .read_flag_mask = 0x80,
};

static int rx6110_i2c_probe(struct i2c_client *client)
{
        struct i2c_adapter *adapter = client->adapter;
        struct rx6110_data *rx6110;

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

        rx6110 = devm_kzalloc(&client->dev, sizeof(*rx6110), GFP_KERNEL);
        if (!rx6110)
                return -ENOMEM;

        rx6110->regmap = devm_regmap_init_i2c(client, &regmap_i2c_config);
        if (IS_ERR(rx6110->regmap)) {
                dev_err(&client->dev, "regmap init failed for rtc rx6110\n");
                return PTR_ERR(rx6110->regmap);
        }

        i2c_set_clientdata(client, rx6110);

        return rx6110_probe(rx6110, &client->dev);
}

static const struct acpi_device_id rx6110_i2c_acpi_match[] = {
        { "SECC6110" },
        { }
};
MODULE_DEVICE_TABLE(acpi, rx6110_i2c_acpi_match);

static const struct i2c_device_id rx6110_i2c_id[] = {
        { "rx6110" },
        { }
};
MODULE_DEVICE_TABLE(i2c, rx6110_i2c_id);

static struct i2c_driver rx6110_i2c_driver = {
        .driver = {
                .name = RX6110_DRIVER_NAME,
                .acpi_match_table = rx6110_i2c_acpi_match,
        },
        .probe          = rx6110_i2c_probe,
        .id_table       = rx6110_i2c_id,
};

static int rx6110_i2c_register(void)
{
        return i2c_add_driver(&rx6110_i2c_driver);
}

static void rx6110_i2c_unregister(void)
{
        i2c_del_driver(&rx6110_i2c_driver);
}
#else
static int rx6110_i2c_register(void)
{
        return 0;
}

static void rx6110_i2c_unregister(void)
{
}
#endif /* CONFIG_I2C */

static int __init rx6110_module_init(void)
{
        int ret;

        ret = rx6110_spi_register();
        if (ret)
                return ret;

        ret = rx6110_i2c_register();
        if (ret)
                rx6110_spi_unregister();

        return ret;
}
module_init(rx6110_module_init);

static void __exit rx6110_module_exit(void)
{
        rx6110_spi_unregister();
        rx6110_i2c_unregister();
}
module_exit(rx6110_module_exit);

MODULE_AUTHOR("Val Krutov <val.krutov@erd.epson.com>");
MODULE_DESCRIPTION("RX-6110 SA RTC driver");
MODULE_LICENSE("GPL");