// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Seiko Instruments S-35390A RTC Driver
 *
 * Copyright (c) 2007 Byron Bradley
 */

#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/i2c.h>
#include <linux/bitrev.h>
#include <linux/bcd.h>
#include <linux/slab.h>
#include <linux/delay.h>

#define S35390A_CMD_STATUS1     0
#define S35390A_CMD_STATUS2     1
#define S35390A_CMD_TIME1       2
#define S35390A_CMD_TIME2       3
#define S35390A_CMD_INT2_REG1   5
#define S35390A_CMD_FREE_REG    7

#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

#define S35390A_ALRM_BYTE_WDAY  0
#define S35390A_ALRM_BYTE_HOURS 1
#define S35390A_ALRM_BYTE_MINS  2

/* flags for STATUS1 */
#define S35390A_FLAG_POC        BIT(0)
#define S35390A_FLAG_BLD        BIT(1)
#define S35390A_FLAG_INT2       BIT(2)
#define S35390A_FLAG_24H        BIT(6)
#define S35390A_FLAG_RESET      BIT(7)

/* flag for STATUS2 */
#define S35390A_FLAG_TEST       BIT(0)

/* INT2 pin output mode */
#define S35390A_INT2_MODE_MASK          0x0E
#define S35390A_INT2_MODE_NOINTR        0x00
#define S35390A_INT2_MODE_ALARM         BIT(1) /* INT2AE */
#define S35390A_INT2_MODE_PMIN_EDG      BIT(2) /* INT2ME */
#define S35390A_INT2_MODE_FREQ          BIT(3) /* INT2FE */
#define S35390A_INT2_MODE_PMIN          (BIT(3) | BIT(2)) /* INT2FE | INT2ME */

static const struct i2c_device_id s35390a_id[] = {
        { "s35390a" },
        { }
};
MODULE_DEVICE_TABLE(i2c, s35390a_id);

static const __maybe_unused struct of_device_id s35390a_of_match[] = {
        { .compatible = "sii,s35390a" },
        { }
};
MODULE_DEVICE_TABLE(of, s35390a_of_match);

struct s35390a {
        struct i2c_client *client[8];
        int twentyfourhour;
};

static int s35390a_set_reg(struct s35390a *s35390a, int reg, u8  *buf, int len)
{
        struct i2c_client *client = s35390a->client[reg];
        struct i2c_msg msg[] = {
                {
                        .addr = client->addr,
                        .len = len,
                        .buf = buf
                },
        };

        if ((i2c_transfer(client->adapter, msg, 1)) != 1)
                return -EIO;

        return 0;
}

static int s35390a_get_reg(struct s35390a *s35390a, int reg, u8 *buf, int len)
{
        struct i2c_client *client = s35390a->client[reg];
        struct i2c_msg msg[] = {
                {
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = len,
                        .buf = buf
                },
        };

        if ((i2c_transfer(client->adapter, msg, 1)) != 1)
                return -EIO;

        return 0;
}

static int s35390a_init(struct s35390a *s35390a)
{
        u8 buf;
        int ret;
        unsigned initcount = 0;

        /*
         * At least one of POC and BLD are set, so reinitialise chip. Keeping
         * this information in the hardware to know later that the time isn't
         * valid is unfortunately not possible because POC and BLD are cleared
         * on read. So the reset is best done now.
         *
         * The 24H bit is kept over reset, so set it already here.
         */
initialize:
        buf = S35390A_FLAG_RESET | S35390A_FLAG_24H;
        ret = s35390a_set_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);

        if (ret < 0)
                return ret;

        ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, &buf, 1);
        if (ret < 0)
                return ret;

        if (buf & (S35390A_FLAG_POC | S35390A_FLAG_BLD)) {
                /* Try up to five times to reset the chip */
                if (initcount < 5) {
                        ++initcount;
                        goto initialize;
                } else
                        return -EIO;
        }

        return 1;
}

/*
 * Returns <0 on error, 0 if rtc is setup fine and 1 if the chip was reset.
 * To keep the information if an irq is pending, pass the value read from
 * STATUS1 to the caller.
 */
static int s35390a_read_status(struct s35390a *s35390a, char *status1)
{
        int ret;

        ret = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, status1, 1);
        if (ret < 0)
                return ret;

        if (*status1 & S35390A_FLAG_POC) {
                /*
                 * Do not communicate for 0.5 seconds since the power-on
                 * detection circuit is in operation.
                 */
                msleep(500);
                return 1;
        } else if (*status1 & S35390A_FLAG_BLD)
                return 1;
        /*
         * If both POC and BLD are unset everything is fine.
         */
        return 0;
}

static int s35390a_disable_test_mode(struct s35390a *s35390a)
{
        u8 buf[1];

        if (s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf)) < 0)
                return -EIO;

        if (!(buf[0] & S35390A_FLAG_TEST))
                return 0;

        buf[0] &= ~S35390A_FLAG_TEST;
        return s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf));
}

static char s35390a_hr2reg(struct s35390a *s35390a, int hour)
{
        if (s35390a->twentyfourhour)
                return bin2bcd(hour);

        if (hour < 12)
                return bin2bcd(hour);

        return 0x40 | bin2bcd(hour - 12);
}

static int s35390a_reg2hr(struct s35390a *s35390a, char reg)
{
        unsigned hour;

        if (s35390a->twentyfourhour)
                return bcd2bin(reg & 0x3f);

        hour = bcd2bin(reg & 0x3f);
        if (reg & 0x40)
                hour += 12;

        return hour;
}

static int s35390a_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct s35390a  *s35390a = i2c_get_clientdata(client);
        int i;
        u8 buf[7], status;

        dev_dbg(&client->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);

        if (s35390a_read_status(s35390a, &status) == 1)
                s35390a_init(s35390a);

        buf[S35390A_BYTE_YEAR] = bin2bcd(tm->tm_year - 100);
        buf[S35390A_BYTE_MONTH] = bin2bcd(tm->tm_mon + 1);
        buf[S35390A_BYTE_DAY] = bin2bcd(tm->tm_mday);
        buf[S35390A_BYTE_WDAY] = bin2bcd(tm->tm_wday);
        buf[S35390A_BYTE_HOURS] = s35390a_hr2reg(s35390a, tm->tm_hour);
        buf[S35390A_BYTE_MINS] = bin2bcd(tm->tm_min);
        buf[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)
                buf[i] = bitrev8(buf[i]);

        return s35390a_set_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
}

static int s35390a_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct s35390a *s35390a = i2c_get_clientdata(client);
        u8 buf[7], status;
        int i, err;

        if (s35390a_read_status(s35390a, &status) == 1)
                return -EINVAL;

        err = s35390a_get_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
        if (err < 0)
                return err;

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

        tm->tm_sec = bcd2bin(buf[S35390A_BYTE_SECS]);
        tm->tm_min = bcd2bin(buf[S35390A_BYTE_MINS]);
        tm->tm_hour = s35390a_reg2hr(s35390a, buf[S35390A_BYTE_HOURS]);
        tm->tm_wday = bcd2bin(buf[S35390A_BYTE_WDAY]);
        tm->tm_mday = bcd2bin(buf[S35390A_BYTE_DAY]);
        tm->tm_mon = bcd2bin(buf[S35390A_BYTE_MONTH]) - 1;
        tm->tm_year = bcd2bin(buf[S35390A_BYTE_YEAR]) + 100;

        dev_dbg(&client->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 s35390a_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct s35390a *s35390a = i2c_get_clientdata(client);
        u8 buf[3], sts = 0;
        int err, i;

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

        /* disable interrupt (which deasserts the irq line) */
        err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
        if (err < 0)
                return err;

        /* clear pending interrupt (in STATUS1 only), if any */
        err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, &sts, sizeof(sts));
        if (err < 0)
                return err;

        if (alm->enabled)
                sts = S35390A_INT2_MODE_ALARM;
        else
                sts = S35390A_INT2_MODE_NOINTR;

        /* set interupt mode*/
        err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
        if (err < 0)
                return err;

        if (alm->time.tm_wday != -1)
                buf[S35390A_ALRM_BYTE_WDAY] = bin2bcd(alm->time.tm_wday) | 0x80;
        else
                buf[S35390A_ALRM_BYTE_WDAY] = 0;

        buf[S35390A_ALRM_BYTE_HOURS] = s35390a_hr2reg(s35390a,
                        alm->time.tm_hour) | 0x80;
        buf[S35390A_ALRM_BYTE_MINS] = bin2bcd(alm->time.tm_min) | 0x80;

        if (alm->time.tm_hour >= 12)
                buf[S35390A_ALRM_BYTE_HOURS] |= 0x40;

        for (i = 0; i < 3; ++i)
                buf[i] = bitrev8(buf[i]);

        err = s35390a_set_reg(s35390a, S35390A_CMD_INT2_REG1, buf,
                                                                sizeof(buf));

        return err;
}

static int s35390a_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct s35390a *s35390a = i2c_get_clientdata(client);
        u8 buf[3], sts;
        int i, err;

        err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, &sts, sizeof(sts));
        if (err < 0)
                return err;

        if ((sts & S35390A_INT2_MODE_MASK) != S35390A_INT2_MODE_ALARM) {
                /*
                 * When the alarm isn't enabled, the register to configure
                 * the alarm time isn't accessible.
                 */
                alm->enabled = 0;
                return 0;
        } else {
                alm->enabled = 1;
        }

        err = s35390a_get_reg(s35390a, S35390A_CMD_INT2_REG1, buf, sizeof(buf));
        if (err < 0)
                return err;

        /* This chip returns the bits of each byte in reverse order */
        for (i = 0; i < 3; ++i)
                buf[i] = bitrev8(buf[i]);

        /*
         * B0 of the three matching registers is an enable flag. Iff it is set
         * the configured value is used for matching.
         */
        if (buf[S35390A_ALRM_BYTE_WDAY] & 0x80)
                alm->time.tm_wday =
                        bcd2bin(buf[S35390A_ALRM_BYTE_WDAY] & ~0x80);

        if (buf[S35390A_ALRM_BYTE_HOURS] & 0x80)
                alm->time.tm_hour =
                        s35390a_reg2hr(s35390a,
                                       buf[S35390A_ALRM_BYTE_HOURS] & ~0x80);

        if (buf[S35390A_ALRM_BYTE_MINS] & 0x80)
                alm->time.tm_min = bcd2bin(buf[S35390A_ALRM_BYTE_MINS] & ~0x80);

        /* alarm triggers always at s=0 */
        alm->time.tm_sec = 0;

        dev_dbg(&client->dev, "%s: alm is mins=%d, hours=%d, wday=%d\n",
                        __func__, alm->time.tm_min, alm->time.tm_hour,
                        alm->time.tm_wday);

        return 0;
}

static int s35390a_rtc_ioctl(struct device *dev, unsigned int cmd,
                             unsigned long arg)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct s35390a *s35390a = i2c_get_clientdata(client);
        u8 sts;
        int err;

        switch (cmd) {
        case RTC_VL_READ:
                /* s35390a_reset set lowvoltage flag and init RTC if needed */
                err = s35390a_read_status(s35390a, &sts);
                if (err < 0)
                        return err;
                if (copy_to_user((void __user *)arg, &err, sizeof(int)))
                        return -EFAULT;
                break;
        case RTC_VL_CLR:
                /* update flag and clear register */
                err = s35390a_init(s35390a);
                if (err < 0)
                        return err;
                break;
        default:
                return -ENOIOCTLCMD;
        }

        return 0;
}

static const struct rtc_class_ops s35390a_rtc_ops = {
        .read_time      = s35390a_rtc_read_time,
        .set_time       = s35390a_rtc_set_time,
        .set_alarm      = s35390a_rtc_set_alarm,
        .read_alarm     = s35390a_rtc_read_alarm,
        .ioctl          = s35390a_rtc_ioctl,
};

static int s35390a_nvmem_read(void *priv, unsigned int offset, void *val,
                              size_t bytes)
{
        struct s35390a *s35390a = priv;

        /* The offset is ignored because the NVMEM region is only 1 byte */
        return s35390a_get_reg(s35390a, S35390A_CMD_FREE_REG, val, bytes);
}

static int s35390a_nvmem_write(void *priv, unsigned int offset, void *val,
                               size_t bytes)
{
        struct s35390a *s35390a = priv;

        return s35390a_set_reg(s35390a, S35390A_CMD_FREE_REG, val, bytes);
}

static int s35390a_probe(struct i2c_client *client)
{
        int err, err_read;
        unsigned int i;
        struct s35390a *s35390a;
        struct rtc_device *rtc;
        u8 buf, status1;
        struct device *dev = &client->dev;
        struct nvmem_config nvmem_cfg = {
                .name = "s35390a_nvram",
                .type = NVMEM_TYPE_BATTERY_BACKED,
                .word_size = 1,
                .stride = 1,
                .size = 1,
                .reg_read = s35390a_nvmem_read,
                .reg_write = s35390a_nvmem_write,
        };

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                return -ENODEV;

        s35390a = devm_kzalloc(dev, sizeof(struct s35390a), GFP_KERNEL);
        if (!s35390a)
                return -ENOMEM;

        s35390a->client[0] = client;
        i2c_set_clientdata(client, s35390a);

        /* This chip uses multiple addresses, use dummy devices for them */
        for (i = 1; i < 8; ++i) {
                s35390a->client[i] = devm_i2c_new_dummy_device(dev,
                                                               client->adapter,
                                                               client->addr + i);
                if (IS_ERR(s35390a->client[i])) {
                        dev_err(dev, "Address %02x unavailable\n",
                                client->addr + i);
                        return PTR_ERR(s35390a->client[i]);
                }
        }

        rtc = devm_rtc_allocate_device(dev);
        if (IS_ERR(rtc))
                return PTR_ERR(rtc);

        err_read = s35390a_read_status(s35390a, &status1);
        if (err_read < 0) {
                dev_err(dev, "error resetting chip\n");
                return err_read;
        }

        if (status1 & S35390A_FLAG_24H)
                s35390a->twentyfourhour = 1;
        else
                s35390a->twentyfourhour = 0;

        if (status1 & S35390A_FLAG_INT2) {
                /* disable alarm (and maybe test mode) */
                buf = 0;
                err = s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, &buf, 1);
                if (err < 0) {
                        dev_err(dev, "error disabling alarm");
                        return err;
                }
        } else {
                err = s35390a_disable_test_mode(s35390a);
                if (err < 0) {
                        dev_err(dev, "error disabling test mode\n");
                        return err;
                }
        }

        device_set_wakeup_capable(dev, 1);

        rtc->ops = &s35390a_rtc_ops;
        rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
        rtc->range_max = RTC_TIMESTAMP_END_2099;

        set_bit(RTC_FEATURE_ALARM_RES_MINUTE, rtc->features);
        clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);

        if (status1 & S35390A_FLAG_INT2)
                rtc_update_irq(rtc, 1, RTC_AF);

        nvmem_cfg.priv = s35390a;
        err = devm_rtc_nvmem_register(rtc, &nvmem_cfg);
        if (err)
                return err;

        return devm_rtc_register_device(rtc);
}

static struct i2c_driver s35390a_driver = {
        .driver         = {
                .name   = "rtc-s35390a",
                .of_match_table = of_match_ptr(s35390a_of_match),
        },
        .probe          = s35390a_probe,
        .id_table       = s35390a_id,
};

module_i2c_driver(s35390a_driver);

MODULE_AUTHOR("Byron Bradley <byron.bbradley@gmail.com>");
MODULE_DESCRIPTION("S35390A RTC driver");
MODULE_LICENSE("GPL");