// SPDX-License-Identifier: GPL-2.0
/*
 * SII Semiconductor Corporation S35392A RTC driver.
 *
 * Copyright (c) 2017, General Electric Company
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <command.h>
#include <common.h>
#include <dm.h>
#include <i2c.h>
#include <linux/bitrev.h>
#include <rtc.h>

#define S35390A_CMD_STATUS1             0x30
#define S35390A_CMD_STATUS2             0x31
#define S35390A_CMD_TIME1               0x32
#define S35390A_CMD_TIME2               0x33
#define S35390A_CMD_INT2_REG1   0x35

#define S35390A_BYTE_YEAR       0
#define S35390A_BYTE_MONTH      1
#define S35390A_BYTE_DAY        2
#define S35390A_BYTE_WDAY       3
#define S35390A_BYTE_HOURS      4
#define S35390A_BYTE_MINS       5
#define S35390A_BYTE_SECS       6

/* flags for STATUS1 */
#define S35390A_FLAG_POC        0x01
#define S35390A_FLAG_BLD        0x02
#define S35390A_FLAG_INT2       0x04
#define S35390A_FLAG_24H        0x40
#define S35390A_FLAG_RESET      0x80

/*
 * If either BLD or POC is set, then the chip has lost power long enough for
 * the time value to become invalid.
 */
#define S35390A_LOW_VOLTAGE (S35390A_FLAG_POC | S35390A_FLAG_BLD)

/*---------------------------------------------------------------------*/
#undef DEBUG_RTC

#ifdef DEBUG_RTC
#define DEBUGR(fmt, args...) printf(fmt, ##args)
#else
#define DEBUGR(fmt, args...)
#endif
/*---------------------------------------------------------------------*/

#ifdef CONFIG_DM_RTC
#define DEV_TYPE struct udevice
#else
/* Local udevice */
struct ludevice {
        u8 chip;
};

#define DEV_TYPE struct ludevice
struct ludevice dev;

#endif

#define msleep(a) udelay(a * 1000)

int lowvoltage;

static int s35392a_rtc_reset(DEV_TYPE *dev);

static int s35392a_rtc_read(DEV_TYPE *dev, u8 reg, u8 *buf, int len)
{
        int ret;

#ifdef CONFIG_DM_RTC
        /* TODO: we need to tweak the chip address to reg */
        ret = dm_i2c_read(dev, 0, buf, len);
#else
        (void)dev;
        ret = i2c_read(reg, 0, -1, buf, len);
#endif

        return ret;
}

static int s35392a_rtc_write(DEV_TYPE *dev, u8 reg, u8 *buf, int len)
{
        int ret;

#ifdef CONFIG_DM_RTC
        /* TODO: we need to tweak the chip address to reg */
        ret = dm_i2c_write(dev, 0, buf, 1);
#else
        (void)dev;
        ret = i2c_write(reg, 0, 0, buf, len);
#endif

        return ret;
}

static int s35392a_rtc_read8(DEV_TYPE *dev, unsigned int reg)
{
        u8 val;
        int ret;

        ret = s35392a_rtc_read(dev, reg, &val, sizeof(val));
        return ret < 0 ? ret : val;
}

static int s35392a_rtc_write8(DEV_TYPE *dev, unsigned int reg, int val)
{
        int ret;
        u8 lval = val;

        ret = s35392a_rtc_write(dev, reg, &lval, sizeof(lval));
        return ret < 0 ? ret : 0;
}

static int validate_time(const struct rtc_time *tm)
{
        if ((tm->tm_year < 2000) || (tm->tm_year > 2099))
                return -EINVAL;

        if ((tm->tm_mon < 1) || (tm->tm_mon > 12))
                return -EINVAL;

        if ((tm->tm_mday < 1) || (tm->tm_mday > 31))
                return -EINVAL;

        if ((tm->tm_wday < 0) || (tm->tm_wday > 6))
                return -EINVAL;

        if ((tm->tm_hour < 0) || (tm->tm_hour > 23))
                return -EINVAL;

        if ((tm->tm_min < 0) || (tm->tm_min > 59))
                return -EINVAL;

        if ((tm->tm_sec < 0) || (tm->tm_sec > 59))
                return -EINVAL;

        return 0;
}

void s35392a_rtc_init(DEV_TYPE *dev)
{
        int status;

        status = s35392a_rtc_read8(dev, S35390A_CMD_STATUS1);
        if (status < 0)
                goto error;

        DEBUGR("init: S35390A_CMD_STATUS1: 0x%x\n", status);

        lowvoltage = status & S35390A_LOW_VOLTAGE ? 1 : 0;

        if (status & S35390A_FLAG_POC)
                /*
                 * Do not communicate for 0.5 seconds since the power-on
                 * detection circuit is in operation.
                 */
                msleep(500);

        else if (!lowvoltage)
                /*
                 * If both POC and BLD are unset everything is fine.
                 */
                return;

        if (lowvoltage)
                printf("RTC low voltage detected\n");

        if (!s35392a_rtc_reset(dev))
                return;

error:
        printf("Error RTC init.\n");
}

/* Get the current time from the RTC */
static int s35392a_rtc_get(DEV_TYPE *dev, struct rtc_time *tm)
{
        u8 date[7];
        int ret, i;

        if (lowvoltage) {
                DEBUGR("RTC low voltage detected\n");
                return -EINVAL;
        }

        ret = s35392a_rtc_read(dev, S35390A_CMD_TIME1, date, sizeof(date));
        if (ret < 0) {
                DEBUGR("Error reading date from RTC\n");
                return -EIO;
        }

        /* This chip returns the bits of each byte in reverse order */
        for (i = 0; i < 7; ++i)
                date[i] = bitrev8(date[i]);

        tm->tm_sec  = bcd2bin(date[S35390A_BYTE_SECS]);
        tm->tm_min  = bcd2bin(date[S35390A_BYTE_MINS]);
        tm->tm_hour = bcd2bin(date[S35390A_BYTE_HOURS] & ~S35390A_FLAG_24H);
        tm->tm_wday = bcd2bin(date[S35390A_BYTE_WDAY]);
        tm->tm_mday = bcd2bin(date[S35390A_BYTE_DAY]);
        tm->tm_mon  = bcd2bin(date[S35390A_BYTE_MONTH]);
        tm->tm_year = bcd2bin(date[S35390A_BYTE_YEAR]) + 2000;

        DEBUGR("Get DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
               tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_wday,
               tm->tm_hour, tm->tm_min, tm->tm_sec);

        return 0;
}

/* Set the RTC */
static int s35392a_rtc_set(DEV_TYPE *dev, const struct rtc_time *tm)
{
        int i, ret;
        int status;
        u8 date[7];

        DEBUGR("Set DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
               tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_wday,
               tm->tm_hour, tm->tm_min, tm->tm_sec);

        ret = validate_time(tm);
        if (ret < 0)
                return -EINVAL;

        /* We support only 24h mode */
        ret = s35392a_rtc_read8(dev, S35390A_CMD_STATUS1);
        if (ret < 0)
                return -EIO;
        status = ret;

        ret = s35392a_rtc_write8(dev, S35390A_CMD_STATUS1,
                                 status | S35390A_FLAG_24H);
        if (ret < 0)
                return -EIO;

        date[S35390A_BYTE_YEAR]  = bin2bcd(tm->tm_year - 2000);
        date[S35390A_BYTE_MONTH] = bin2bcd(tm->tm_mon);
        date[S35390A_BYTE_DAY]   = bin2bcd(tm->tm_mday);
        date[S35390A_BYTE_WDAY]  = bin2bcd(tm->tm_wday);
        date[S35390A_BYTE_HOURS] = bin2bcd(tm->tm_hour);
        date[S35390A_BYTE_MINS]  = bin2bcd(tm->tm_min);
        date[S35390A_BYTE_SECS]  = bin2bcd(tm->tm_sec);

        /* This chip expects the bits of each byte to be in reverse order */
        for (i = 0; i < 7; ++i)
                date[i] = bitrev8(date[i]);

        ret = s35392a_rtc_write(dev, S35390A_CMD_TIME1, date, sizeof(date));
        if (ret < 0) {
                DEBUGR("Error writing date to RTC\n");
                return -EIO;
        }

        /* Now we have time. Reset the low voltage status */
        lowvoltage = 0;

        return 0;
}

/* Reset the RTC. */
static int s35392a_rtc_reset(DEV_TYPE *dev)
{
        int buf;
        int ret;
        unsigned int initcount = 0;

        buf = S35390A_FLAG_RESET;

initialize:
        ret = s35392a_rtc_write8(dev, S35390A_CMD_STATUS1, buf);
        if (ret < 0)
                return -EIO;

        ret = s35392a_rtc_read8(dev, S35390A_CMD_STATUS1);
        if (ret < 0)
                return -EIO;
        buf = ret;

        if (!lowvoltage)
                lowvoltage = buf & S35390A_LOW_VOLTAGE ? 1 : 0;

        if (buf & S35390A_LOW_VOLTAGE) {
                /* Try up to five times to reset the chip */
                if (initcount < 5) {
                        ++initcount;
                        goto initialize;
                } else {
                        return -EIO;
                }
        }

        return 0;
}

#ifndef CONFIG_DM_RTC

int rtc_get(struct rtc_time *tm)
{
        return s35392a_rtc_get(&dev, tm);
}

int rtc_set(struct rtc_time *tm)
{
        return s35392a_rtc_set(&dev, tm);
}

void rtc_reset(void)
{
        s35392a_rtc_reset(&dev);
}

void rtc_init(void)
{
        s35392a_rtc_init(&dev);
}

#else

static int s35392a_probe(struct udevice *dev)
{
        s35392a_rtc_init(dev);
        return 0;
}

static const struct rtc_ops s35392a_rtc_ops = {
        .get = s35392a_rtc_get,
        .set = s35392a_rtc_set,
        .read8 = s35392a_rtc_read8,
        .write8 = s35392a_rtc_write8,
        .reset = s35392a_rtc_reset,
};

static const struct udevice_id s35392a_rtc_ids[] = {
        { .compatible = "sii,s35392a-rtc" },
        { }
};

U_BOOT_DRIVER(s35392a_rtc) = {
        .name     = "s35392a_rtc",
        .id           = UCLASS_RTC,
        .probe    = s35392a_probe,
        .of_match = s35392a_rtc_ids,
        .ops      = &s35392a_rtc_ops,
};

#endif