// SPDX-License-Identifier: GPL-2.0-only
/*
 * An I2C driver for the Epson RX8581 RTC
 *
 * Author: Martyn Welch <martyn.welch@ge.com>
 * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
 *
 * Based on: rtc-pcf8563.c (An I2C driver for the Philips PCF8563 RTC)
 * Copyright 2005-06 Tower Technologies
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/bcd.h>
#include <linux/of.h>
#include <linux/regmap.h>
#include <linux/rtc.h>
#include <linux/log2.h>

#define RX8581_REG_SC           0x00 /* Second in BCD */
#define RX8581_REG_MN           0x01 /* Minute in BCD */
#define RX8581_REG_HR           0x02 /* Hour in BCD */
#define RX8581_REG_DW           0x03 /* Day of Week */
#define RX8581_REG_DM           0x04 /* Day of Month in BCD */
#define RX8581_REG_MO           0x05 /* Month in BCD */
#define RX8581_REG_YR           0x06 /* Year in BCD */
#define RX8581_REG_RAM          0x07 /* RAM */
#define RX8581_REG_AMN          0x08 /* Alarm Min in BCD*/
#define RX8581_REG_AHR          0x09 /* Alarm Hour in BCD */
#define RX8581_REG_ADM          0x0A
#define RX8581_REG_ADW          0x0A
#define RX8581_REG_TMR0         0x0B
#define RX8581_REG_TMR1         0x0C
#define RX8581_REG_EXT          0x0D /* Extension Register */
#define RX8581_REG_FLAG         0x0E /* Flag Register */
#define RX8581_REG_CTRL         0x0F /* Control Register */


/* Flag Register bit definitions */
#define RX8581_FLAG_UF          0x20 /* Update */
#define RX8581_FLAG_TF          0x10 /* Timer */
#define RX8581_FLAG_AF          0x08 /* Alarm */
#define RX8581_FLAG_VLF         0x02 /* Voltage Low */

/* Control Register bit definitions */
#define RX8581_CTRL_UIE         0x20 /* Update Interrupt Enable */
#define RX8581_CTRL_TIE         0x10 /* Timer Interrupt Enable */
#define RX8581_CTRL_AIE         0x08 /* Alarm Interrupt Enable */
#define RX8581_CTRL_STOP        0x02 /* STOP bit */
#define RX8581_CTRL_RESET       0x01 /* RESET bit */

#define RX8571_USER_RAM         0x10
#define RX8571_NVRAM_SIZE       0x10

struct rx85x1_config {
        struct regmap_config regmap;
        unsigned int num_nvram;
};

/*
 * In the routines that deal directly with the rx8581 hardware, we use
 * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
 */
static int rx8581_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        unsigned char date[7];
        unsigned int data;
        int err;
        struct regmap *regmap = i2c_get_clientdata(client);

        /* First we ensure that the "update flag" is not set, we read the
         * time and date then re-read the "update flag". If the update flag
         * has been set, we know that the time has changed during the read so
         * we repeat the whole process again.
         */
        err = regmap_read(regmap, RX8581_REG_FLAG, &data);
        if (err < 0)
                return err;

        if (data & RX8581_FLAG_VLF) {
                dev_warn(dev,
                         "low voltage detected, date/time is not reliable.\n");
                return -EINVAL;
        }

        do {
                /* If update flag set, clear it */
                if (data & RX8581_FLAG_UF) {
                        err = regmap_write(regmap, RX8581_REG_FLAG,
                                           data & ~RX8581_FLAG_UF);
                        if (err < 0)
                                return err;
                }

                /* Now read time and date */
                err = regmap_bulk_read(regmap, RX8581_REG_SC, date,
                                       sizeof(date));
                if (err < 0)
                        return err;

                /* Check flag register */
                err = regmap_read(regmap, RX8581_REG_FLAG, &data);
                if (err < 0)
                        return err;
        } while (data & RX8581_FLAG_UF);

        dev_dbg(dev, "%s: raw data is sec=%02x, min=%02x, hr=%02x, "
                "wday=%02x, mday=%02x, mon=%02x, year=%02x\n",
                __func__,
                date[0], date[1], date[2], date[3], date[4], date[5], date[6]);

        tm->tm_sec = bcd2bin(date[RX8581_REG_SC] & 0x7F);
        tm->tm_min = bcd2bin(date[RX8581_REG_MN] & 0x7F);
        tm->tm_hour = bcd2bin(date[RX8581_REG_HR] & 0x3F); /* rtc hr 0-23 */
        tm->tm_wday = ilog2(date[RX8581_REG_DW] & 0x7F);
        tm->tm_mday = bcd2bin(date[RX8581_REG_DM] & 0x3F);
        tm->tm_mon = bcd2bin(date[RX8581_REG_MO] & 0x1F) - 1; /* rtc mn 1-12 */
        tm->tm_year = bcd2bin(date[RX8581_REG_YR]) + 100;

        dev_dbg(dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
                "mday=%d, mon=%d, year=%d, wday=%d\n",
                __func__,
                tm->tm_sec, tm->tm_min, tm->tm_hour,
                tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);

        return 0;
}

static int rx8581_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        int err;
        unsigned char buf[7];
        struct regmap *regmap = i2c_get_clientdata(client);

        dev_dbg(dev, "%s: secs=%d, mins=%d, hours=%d, "
                "mday=%d, mon=%d, year=%d, wday=%d\n",
                __func__,
                tm->tm_sec, tm->tm_min, tm->tm_hour,
                tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);

        /* hours, minutes and seconds */
        buf[RX8581_REG_SC] = bin2bcd(tm->tm_sec);
        buf[RX8581_REG_MN] = bin2bcd(tm->tm_min);
        buf[RX8581_REG_HR] = bin2bcd(tm->tm_hour);

        buf[RX8581_REG_DM] = bin2bcd(tm->tm_mday);

        /* month, 1 - 12 */
        buf[RX8581_REG_MO] = bin2bcd(tm->tm_mon + 1);

        /* year and century */
        buf[RX8581_REG_YR] = bin2bcd(tm->tm_year - 100);
        buf[RX8581_REG_DW] = (0x1 << tm->tm_wday);

        /* Stop the clock */
        err = regmap_update_bits(regmap, RX8581_REG_CTRL,
                                 RX8581_CTRL_STOP, RX8581_CTRL_STOP);
        if (err < 0)
                return err;

        /* write register's data */
        err = regmap_bulk_write(regmap, RX8581_REG_SC, buf, sizeof(buf));
        if (err < 0)
                return err;

        /* get VLF and clear it */
        err = regmap_update_bits(regmap, RX8581_REG_FLAG, RX8581_FLAG_VLF, 0);
        if (err < 0)
                return err;

        /* Restart the clock */
        return regmap_update_bits(regmap, RX8581_REG_CTRL,
                                 RX8581_CTRL_STOP, 0);
}

static const struct rtc_class_ops rx8581_rtc_ops = {
        .read_time      = rx8581_rtc_read_time,
        .set_time       = rx8581_rtc_set_time,
};

static int rx8571_nvram_read(void *priv, unsigned int offset, void *val,
                             size_t bytes)
{
        struct regmap *regmap = priv;

        return regmap_bulk_read(regmap, RX8571_USER_RAM + offset, val, bytes);
}

static int rx8571_nvram_write(void *priv, unsigned int offset, void *val,
                              size_t bytes)
{
        struct regmap *regmap = priv;

        return regmap_bulk_write(regmap, RX8571_USER_RAM + offset, val, bytes);
}

static int rx85x1_nvram_read(void *priv, unsigned int offset, void *val,
                             size_t bytes)
{
        struct regmap *regmap = priv;
        unsigned int tmp_val;
        int ret;

        ret = regmap_read(regmap, RX8581_REG_RAM, &tmp_val);
        (*(unsigned char *)val) = (unsigned char) tmp_val;

        return ret;
}

static int rx85x1_nvram_write(void *priv, unsigned int offset, void *val,
                              size_t bytes)
{
        struct regmap *regmap = priv;
        unsigned char tmp_val;

        tmp_val = *((unsigned char *)val);
        return regmap_write(regmap, RX8581_REG_RAM, (unsigned int)tmp_val);
}

static const struct rx85x1_config rx8581_config = {
        .regmap = {
                .reg_bits = 8,
                .val_bits = 8,
                .max_register = 0xf,
        },
        .num_nvram = 1
};

static const struct rx85x1_config rx8571_config = {
        .regmap = {
                .reg_bits = 8,
                .val_bits = 8,
                .max_register = 0x1f,
        },
        .num_nvram = 2
};

static int rx8581_probe(struct i2c_client *client)
{
        struct regmap *regmap;
        const struct rx85x1_config *config = &rx8581_config;
        const void *data = of_device_get_match_data(&client->dev);
        struct rtc_device *rtc;
        static struct nvmem_config nvmem_cfg[] = {
                {
                        .name = "rx85x1-",
                        .word_size = 1,
                        .stride = 1,
                        .size = 1,
                        .reg_read = rx85x1_nvram_read,
                        .reg_write = rx85x1_nvram_write,
                }, {
                        .name = "rx8571-",
                        .word_size = 1,
                        .stride = 1,
                        .size = RX8571_NVRAM_SIZE,
                        .reg_read = rx8571_nvram_read,
                        .reg_write = rx8571_nvram_write,
                },
        };
        int ret, i;

        dev_dbg(&client->dev, "%s\n", __func__);

        if (data)
                config = data;

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

        i2c_set_clientdata(client, regmap);

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

        rtc->ops = &rx8581_rtc_ops;
        rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
        rtc->range_max = RTC_TIMESTAMP_END_2099;
        rtc->start_secs = 0;
        rtc->set_start_time = true;

        ret = devm_rtc_register_device(rtc);

        for (i = 0; i < config->num_nvram; i++) {
                nvmem_cfg[i].priv = regmap;
                devm_rtc_nvmem_register(rtc, &nvmem_cfg[i]);
        }

        return ret;
}

static const struct i2c_device_id rx8581_id[] = {
        { "rx8581" },
        { }
};
MODULE_DEVICE_TABLE(i2c, rx8581_id);

static const __maybe_unused struct of_device_id rx8581_of_match[] = {
        { .compatible = "epson,rx8571", .data = &rx8571_config },
        { .compatible = "epson,rx8581", .data = &rx8581_config },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, rx8581_of_match);

static struct i2c_driver rx8581_driver = {
        .driver         = {
                .name   = "rtc-rx8581",
                .of_match_table = of_match_ptr(rx8581_of_match),
        },
        .probe          = rx8581_probe,
        .id_table       = rx8581_id,
};

module_i2c_driver(rx8581_driver);

MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
MODULE_DESCRIPTION("Epson RX-8571/RX-8581 RTC driver");
MODULE_LICENSE("GPL");