// SPDX-License-Identifier: GPL-2.0-only
/*
 * An I2C driver for Ricoh RS5C372, R2025S/D and RV5C38[67] RTCs
 *
 * Copyright (C) 2005 Pavel Mironchik <pmironchik@optifacio.net>
 * Copyright (C) 2006 Tower Technologies
 * Copyright (C) 2008 Paul Mundt
 */

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

/*
 * Ricoh has a family of I2C based RTCs, which differ only slightly from
 * each other.  Differences center on pinout (e.g. how many interrupts,
 * output clock, etc) and how the control registers are used.  The '372
 * is significant only because that's the one this driver first supported.
 */
#define RS5C372_REG_SECS        0
#define RS5C372_REG_MINS        1
#define RS5C372_REG_HOURS       2
#define RS5C372_REG_WDAY        3
#define RS5C372_REG_DAY         4
#define RS5C372_REG_MONTH       5
#define RS5C372_REG_YEAR        6
#define RS5C372_REG_TRIM        7
#       define RS5C372_TRIM_XSL         0x80            /* only if RS5C372[a|b] */
#       define RS5C372_TRIM_MASK        0x7F
#       define R2221TL_TRIM_DEV         (1 << 7)        /* only if R2221TL */
#       define RS5C372_TRIM_DECR        (1 << 6)

#define RS5C_REG_ALARM_A_MIN    8                       /* or ALARM_W */
#define RS5C_REG_ALARM_A_HOURS  9
#define RS5C_REG_ALARM_A_WDAY   10

#define RS5C_REG_ALARM_B_MIN    11                      /* or ALARM_D */
#define RS5C_REG_ALARM_B_HOURS  12
#define RS5C_REG_ALARM_B_WDAY   13                      /* (ALARM_B only) */

#define RS5C_REG_CTRL1          14
#       define RS5C_CTRL1_AALE          (1 << 7)        /* or WALE */
#       define RS5C_CTRL1_BALE          (1 << 6)        /* or DALE */
#       define RV5C387_CTRL1_24         (1 << 5)
#       define RS5C372A_CTRL1_SL1       (1 << 5)
#       define RS5C_CTRL1_CT_MASK       (7 << 0)
#       define RS5C_CTRL1_CT0           (0 << 0)        /* no periodic irq */
#       define RS5C_CTRL1_CT4           (4 << 0)        /* 1 Hz level irq */
#define RS5C_REG_CTRL2          15
#       define RS5C372_CTRL2_24         (1 << 5)
#       define RS5C_CTRL2_XSTP          (1 << 4)        /* only if !R2x2x */
#       define R2x2x_CTRL2_VDET         (1 << 6)        /* only if  R2x2x */
#       define R2x2x_CTRL2_XSTP         (1 << 5)        /* only if  R2x2x */
#       define R2x2x_CTRL2_PON          (1 << 4)        /* only if  R2x2x */
#       define RS5C_CTRL2_CTFG          (1 << 2)
#       define RS5C_CTRL2_AAFG          (1 << 1)        /* or WAFG */
#       define RS5C_CTRL2_BAFG          (1 << 0)        /* or DAFG */


/* to read (style 1) or write registers starting at R */
#define RS5C_ADDR(R)            (((R) << 4) | 0)


enum rtc_type {
        rtc_undef = 0,
        rtc_r2025sd,
        rtc_r2221tl,
        rtc_rs5c372a,
        rtc_rs5c372b,
        rtc_rv5c386,
        rtc_rv5c387a,
};

static const struct i2c_device_id rs5c372_id[] = {
        { "r2025sd", rtc_r2025sd },
        { "r2221tl", rtc_r2221tl },
        { "rs5c372a", rtc_rs5c372a },
        { "rs5c372b", rtc_rs5c372b },
        { "rv5c386", rtc_rv5c386 },
        { "rv5c387a", rtc_rv5c387a },
        { }
};
MODULE_DEVICE_TABLE(i2c, rs5c372_id);

static const __maybe_unused struct of_device_id rs5c372_of_match[] = {
        {
                .compatible = "ricoh,r2025sd",
                .data = (void *)rtc_r2025sd
        },
        {
                .compatible = "ricoh,r2221tl",
                .data = (void *)rtc_r2221tl
        },
        {
                .compatible = "ricoh,rs5c372a",
                .data = (void *)rtc_rs5c372a
        },
        {
                .compatible = "ricoh,rs5c372b",
                .data = (void *)rtc_rs5c372b
        },
        {
                .compatible = "ricoh,rv5c386",
                .data = (void *)rtc_rv5c386
        },
        {
                .compatible = "ricoh,rv5c387a",
                .data = (void *)rtc_rv5c387a
        },
        { }
};
MODULE_DEVICE_TABLE(of, rs5c372_of_match);

/* REVISIT:  this assumes that:
 *  - we're in the 21st century, so it's safe to ignore the century
 *    bit for rv5c38[67] (REG_MONTH bit 7);
 *  - we should use ALARM_A not ALARM_B (may be wrong on some boards)
 */
struct rs5c372 {
        struct i2c_client       *client;
        struct rtc_device       *rtc;
        enum rtc_type           type;
        unsigned                time24:1;
        unsigned                has_irq:1;
        unsigned                smbus:1;
        char                    buf[17];
        char                    *regs;
};

static int rs5c_get_regs(struct rs5c372 *rs5c)
{
        struct i2c_client       *client = rs5c->client;
        struct i2c_msg          msgs[] = {
                {
                        .addr = client->addr,
                        .flags = I2C_M_RD,
                        .len = sizeof(rs5c->buf),
                        .buf = rs5c->buf
                },
        };

        /* This implements the third reading method from the datasheet, using
         * an internal address that's reset after each transaction (by STOP)
         * to 0x0f ... so we read extra registers, and skip the first one.
         *
         * The first method doesn't work with the iop3xx adapter driver, on at
         * least 80219 chips; this works around that bug.
         *
         * The third method on the other hand doesn't work for the SMBus-only
         * configurations, so we use the first method there, stripping off
         * the extra register in the process.
         */
        if (rs5c->smbus) {
                int addr = RS5C_ADDR(RS5C372_REG_SECS);
                int size = sizeof(rs5c->buf) - 1;

                if (i2c_smbus_read_i2c_block_data(client, addr, size,
                                                  rs5c->buf + 1) != size) {
                        dev_warn(&client->dev, "can't read registers\n");
                        return -EIO;
                }
        } else {
                if ((i2c_transfer(client->adapter, msgs, 1)) != 1) {
                        dev_warn(&client->dev, "can't read registers\n");
                        return -EIO;
                }
        }

        dev_dbg(&client->dev,
                "%3ph (%02x) %3ph (%02x), %3ph, %3ph; %02x %02x\n",
                rs5c->regs + 0, rs5c->regs[3],
                rs5c->regs + 4, rs5c->regs[7],
                rs5c->regs + 8, rs5c->regs + 11,
                rs5c->regs[14], rs5c->regs[15]);

        return 0;
}

static unsigned rs5c_reg2hr(struct rs5c372 *rs5c, unsigned reg)
{
        unsigned        hour;

        if (rs5c->time24)
                return bcd2bin(reg & 0x3f);

        hour = bcd2bin(reg & 0x1f);
        if (hour == 12)
                hour = 0;
        if (reg & 0x20)
                hour += 12;
        return hour;
}

static unsigned rs5c_hr2reg(struct rs5c372 *rs5c, unsigned hour)
{
        if (rs5c->time24)
                return bin2bcd(hour);

        if (hour > 12)
                return 0x20 | bin2bcd(hour - 12);
        if (hour == 12)
                return 0x20 | bin2bcd(12);
        if (hour == 0)
                return bin2bcd(12);
        return bin2bcd(hour);
}

static int rs5c372_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct rs5c372  *rs5c = i2c_get_clientdata(client);
        int             status = rs5c_get_regs(rs5c);
        unsigned char ctrl2 = rs5c->regs[RS5C_REG_CTRL2];

        if (status < 0)
                return status;

        switch (rs5c->type) {
        case rtc_r2025sd:
        case rtc_r2221tl:
                if ((rs5c->type == rtc_r2025sd && !(ctrl2 & R2x2x_CTRL2_XSTP)) ||
                    (rs5c->type == rtc_r2221tl &&  (ctrl2 & R2x2x_CTRL2_XSTP))) {
                        dev_warn(&client->dev, "rtc oscillator interruption detected. Please reset the rtc clock.\n");
                        return -EINVAL;
                }
                break;
        default:
                if (ctrl2 & RS5C_CTRL2_XSTP) {
                        dev_warn(&client->dev, "rtc oscillator interruption detected. Please reset the rtc clock.\n");
                        return -EINVAL;
                }
        }

        tm->tm_sec = bcd2bin(rs5c->regs[RS5C372_REG_SECS] & 0x7f);
        tm->tm_min = bcd2bin(rs5c->regs[RS5C372_REG_MINS] & 0x7f);
        tm->tm_hour = rs5c_reg2hr(rs5c, rs5c->regs[RS5C372_REG_HOURS]);

        tm->tm_wday = bcd2bin(rs5c->regs[RS5C372_REG_WDAY] & 0x07);
        tm->tm_mday = bcd2bin(rs5c->regs[RS5C372_REG_DAY] & 0x3f);

        /* tm->tm_mon is zero-based */
        tm->tm_mon = bcd2bin(rs5c->regs[RS5C372_REG_MONTH] & 0x1f) - 1;

        /* year is 1900 + tm->tm_year */
        tm->tm_year = bcd2bin(rs5c->regs[RS5C372_REG_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 rs5c372_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct rs5c372  *rs5c = i2c_get_clientdata(client);
        unsigned char   buf[7];
        unsigned char   ctrl2;
        int             addr;

        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);

        addr   = RS5C_ADDR(RS5C372_REG_SECS);
        buf[0] = bin2bcd(tm->tm_sec);
        buf[1] = bin2bcd(tm->tm_min);
        buf[2] = rs5c_hr2reg(rs5c, tm->tm_hour);
        buf[3] = bin2bcd(tm->tm_wday);
        buf[4] = bin2bcd(tm->tm_mday);
        buf[5] = bin2bcd(tm->tm_mon + 1);
        buf[6] = bin2bcd(tm->tm_year - 100);

        if (i2c_smbus_write_i2c_block_data(client, addr, sizeof(buf), buf) < 0) {
                dev_dbg(&client->dev, "%s: write error in line %i\n",
                        __func__, __LINE__);
                return -EIO;
        }

        addr = RS5C_ADDR(RS5C_REG_CTRL2);
        ctrl2 = i2c_smbus_read_byte_data(client, addr);

        /* clear rtc warning bits */
        switch (rs5c->type) {
        case rtc_r2025sd:
        case rtc_r2221tl:
                ctrl2 &= ~(R2x2x_CTRL2_VDET | R2x2x_CTRL2_PON);
                if (rs5c->type == rtc_r2025sd)
                        ctrl2 |= R2x2x_CTRL2_XSTP;
                else
                        ctrl2 &= ~R2x2x_CTRL2_XSTP;
                break;
        default:
                ctrl2 &= ~RS5C_CTRL2_XSTP;
                break;
        }

        if (i2c_smbus_write_byte_data(client, addr, ctrl2) < 0) {
                dev_dbg(&client->dev, "%s: write error in line %i\n",
                        __func__, __LINE__);
                return -EIO;
        }

        return 0;
}

#if IS_ENABLED(CONFIG_RTC_INTF_PROC)
#define NEED_TRIM
#endif

#if IS_ENABLED(CONFIG_RTC_INTF_SYSFS)
#define NEED_TRIM
#endif

#ifdef  NEED_TRIM
static int rs5c372_get_trim(struct i2c_client *client, int *osc, int *trim)
{
        struct rs5c372 *rs5c372 = i2c_get_clientdata(client);
        u8 tmp = rs5c372->regs[RS5C372_REG_TRIM];

        if (osc) {
                if (rs5c372->type == rtc_rs5c372a || rs5c372->type == rtc_rs5c372b)
                        *osc = (tmp & RS5C372_TRIM_XSL) ? 32000 : 32768;
                else
                        *osc = 32768;
        }

        if (trim) {
                dev_dbg(&client->dev, "%s: raw trim=%x\n", __func__, tmp);
                tmp &= RS5C372_TRIM_MASK;
                if (tmp & 0x3e) {
                        int t = tmp & 0x3f;

                        if (tmp & 0x40)
                                t = (~t | (s8)0xc0) + 1;
                        else
                                t = t - 1;

                        tmp = t * 2;
                } else
                        tmp = 0;
                *trim = tmp;
        }

        return 0;
}
#endif

static int rs5c_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct i2c_client       *client = to_i2c_client(dev);
        struct rs5c372          *rs5c = i2c_get_clientdata(client);
        unsigned char           buf;
        int                     status, addr;

        buf = rs5c->regs[RS5C_REG_CTRL1];

        if (!rs5c->has_irq)
                return -EINVAL;

        status = rs5c_get_regs(rs5c);
        if (status < 0)
                return status;

        addr = RS5C_ADDR(RS5C_REG_CTRL1);
        if (enabled)
                buf |= RS5C_CTRL1_AALE;
        else
                buf &= ~RS5C_CTRL1_AALE;

        if (i2c_smbus_write_byte_data(client, addr, buf) < 0) {
                dev_warn(dev, "can't update alarm\n");
                status = -EIO;
        } else
                rs5c->regs[RS5C_REG_CTRL1] = buf;

        return status;
}


/* NOTE:  Since RTC_WKALM_{RD,SET} were originally defined for EFI,
 * which only exposes a polled programming interface; and since
 * these calls map directly to those EFI requests; we don't demand
 * we have an IRQ for this chip when we go through this API.
 *
 * The older x86_pc derived RTC_ALM_{READ,SET} calls require irqs
 * though, managed through RTC_AIE_{ON,OFF} requests.
 */

static int rs5c_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct i2c_client       *client = to_i2c_client(dev);
        struct rs5c372          *rs5c = i2c_get_clientdata(client);
        int                     status;

        status = rs5c_get_regs(rs5c);
        if (status < 0)
                return status;

        /* report alarm time */
        t->time.tm_sec = 0;
        t->time.tm_min = bcd2bin(rs5c->regs[RS5C_REG_ALARM_A_MIN] & 0x7f);
        t->time.tm_hour = rs5c_reg2hr(rs5c, rs5c->regs[RS5C_REG_ALARM_A_HOURS]);

        /* ... and status */
        t->enabled = !!(rs5c->regs[RS5C_REG_CTRL1] & RS5C_CTRL1_AALE);
        t->pending = !!(rs5c->regs[RS5C_REG_CTRL2] & RS5C_CTRL2_AAFG);

        return 0;
}

static int rs5c_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct i2c_client       *client = to_i2c_client(dev);
        struct rs5c372          *rs5c = i2c_get_clientdata(client);
        int                     status, addr, i;
        unsigned char           buf[3];

        /* only handle up to 24 hours in the future, like RTC_ALM_SET */
        if (t->time.tm_mday != -1
                        || t->time.tm_mon != -1
                        || t->time.tm_year != -1)
                return -EINVAL;

        /* REVISIT: round up tm_sec */

        /* if needed, disable irq (clears pending status) */
        status = rs5c_get_regs(rs5c);
        if (status < 0)
                return status;
        if (rs5c->regs[RS5C_REG_CTRL1] & RS5C_CTRL1_AALE) {
                addr = RS5C_ADDR(RS5C_REG_CTRL1);
                buf[0] = rs5c->regs[RS5C_REG_CTRL1] & ~RS5C_CTRL1_AALE;
                if (i2c_smbus_write_byte_data(client, addr, buf[0]) < 0) {
                        dev_dbg(dev, "can't disable alarm\n");
                        return -EIO;
                }
                rs5c->regs[RS5C_REG_CTRL1] = buf[0];
        }

        /* set alarm */
        buf[0] = bin2bcd(t->time.tm_min);
        buf[1] = rs5c_hr2reg(rs5c, t->time.tm_hour);
        buf[2] = 0x7f;  /* any/all days */

        for (i = 0; i < sizeof(buf); i++) {
                addr = RS5C_ADDR(RS5C_REG_ALARM_A_MIN + i);
                if (i2c_smbus_write_byte_data(client, addr, buf[i]) < 0) {
                        dev_dbg(dev, "can't set alarm time\n");
                        return -EIO;
                }
        }

        /* ... and maybe enable its irq */
        if (t->enabled) {
                addr = RS5C_ADDR(RS5C_REG_CTRL1);
                buf[0] = rs5c->regs[RS5C_REG_CTRL1] | RS5C_CTRL1_AALE;
                if (i2c_smbus_write_byte_data(client, addr, buf[0]) < 0)
                        dev_warn(dev, "can't enable alarm\n");
                rs5c->regs[RS5C_REG_CTRL1] = buf[0];
        }

        return 0;
}

#if IS_ENABLED(CONFIG_RTC_INTF_PROC)

static int rs5c372_rtc_proc(struct device *dev, struct seq_file *seq)
{
        int err, osc, trim;

        err = rs5c372_get_trim(to_i2c_client(dev), &osc, &trim);
        if (err == 0) {
                seq_printf(seq, "crystal\t\t: %d.%03d KHz\n",
                                osc / 1000, osc % 1000);
                seq_printf(seq, "trim\t\t: %d\n", trim);
        }

        return 0;
}

#else
#define rs5c372_rtc_proc        NULL
#endif

#ifdef CONFIG_RTC_INTF_DEV
static int rs5c372_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
        struct rs5c372  *rs5c = i2c_get_clientdata(to_i2c_client(dev));
        unsigned char   ctrl2;
        int             addr;
        unsigned int    flags;

        dev_dbg(dev, "%s: cmd=%x\n", __func__, cmd);

        addr = RS5C_ADDR(RS5C_REG_CTRL2);
        ctrl2 = i2c_smbus_read_byte_data(rs5c->client, addr);

        switch (cmd) {
        case RTC_VL_READ:
                flags = 0;

                switch (rs5c->type) {
                case rtc_r2025sd:
                case rtc_r2221tl:
                        if ((rs5c->type == rtc_r2025sd && !(ctrl2 & R2x2x_CTRL2_XSTP)) ||
                                (rs5c->type == rtc_r2221tl &&  (ctrl2 & R2x2x_CTRL2_XSTP))) {
                                flags |= RTC_VL_DATA_INVALID;
                        }
                        if (ctrl2 & R2x2x_CTRL2_VDET)
                                flags |= RTC_VL_BACKUP_LOW;
                        break;
                default:
                        if (ctrl2 & RS5C_CTRL2_XSTP)
                                flags |= RTC_VL_DATA_INVALID;
                        break;
                }

                return put_user(flags, (unsigned int __user *)arg);
        case RTC_VL_CLR:
                /* clear VDET bit */
                if (rs5c->type == rtc_r2025sd || rs5c->type == rtc_r2221tl) {
                        ctrl2 &= ~R2x2x_CTRL2_VDET;
                        if (i2c_smbus_write_byte_data(rs5c->client, addr, ctrl2) < 0) {
                                dev_dbg(&rs5c->client->dev, "%s: write error in line %i\n",
                                                __func__, __LINE__);
                                return -EIO;
                        }
                }
                return 0;
        default:
                return -ENOIOCTLCMD;
        }
        return 0;
}
#else
#define rs5c372_ioctl   NULL
#endif

static int rs5c372_read_offset(struct device *dev, long *offset)
{
        struct rs5c372 *rs5c = i2c_get_clientdata(to_i2c_client(dev));
        u8 val = rs5c->regs[RS5C372_REG_TRIM];
        long ppb_per_step = 0;
        bool decr = val & RS5C372_TRIM_DECR;

        switch (rs5c->type) {
        case rtc_r2221tl:
                ppb_per_step = val & R2221TL_TRIM_DEV ? 1017 : 3051;
                break;
        case rtc_rs5c372a:
        case rtc_rs5c372b:
                ppb_per_step = val & RS5C372_TRIM_XSL ? 3125 : 3051;
                break;
        default:
                ppb_per_step = 3051;
                break;
        }

        /* Only bits[0:5] repsents the time counts */
        val &= 0x3F;

        /* If bits[1:5] are all 0, it means no increment or decrement */
        if (!(val & 0x3E)) {
                *offset = 0;
        } else {
                if (decr)
                        *offset = -(((~val) & 0x3F) + 1) * ppb_per_step;
                else
                        *offset = (val - 1) * ppb_per_step;
        }

        return 0;
}

static int rs5c372_set_offset(struct device *dev, long offset)
{
        struct rs5c372 *rs5c = i2c_get_clientdata(to_i2c_client(dev));
        int addr = RS5C_ADDR(RS5C372_REG_TRIM);
        u8 val = 0;
        u8 tmp = 0;
        long ppb_per_step = 3051;
        long steps = LONG_MIN;

        switch (rs5c->type) {
        case rtc_rs5c372a:
        case rtc_rs5c372b:
                tmp = rs5c->regs[RS5C372_REG_TRIM];
                if (tmp & RS5C372_TRIM_XSL) {
                        ppb_per_step = 3125;
                        val |= RS5C372_TRIM_XSL;
                }
                break;
        case rtc_r2221tl:
                /*
                 * Check if it is possible to use high resolution mode (DEV=1).
                 * In this mode, the minimum resolution is 2 / (32768 * 20 * 3),
                 * which is about 1017 ppb.
                 */
                steps = DIV_ROUND_CLOSEST(offset, 1017);
                if (steps >= -0x3E && steps <= 0x3E) {
                        ppb_per_step = 1017;
                        val |= R2221TL_TRIM_DEV;
                } else {
                        /*
                         * offset is out of the range of high resolution mode.
                         * Try to use low resolution mode (DEV=0). In this mode,
                         * the minimum resolution is 2 / (32768 * 20), which is
                         * about 3051 ppb.
                         */
                        steps = LONG_MIN;
                }
                break;
        default:
                break;
        }

        if (steps == LONG_MIN) {
                steps = DIV_ROUND_CLOSEST(offset, ppb_per_step);
                if (steps > 0x3E || steps < -0x3E)
                        return -ERANGE;
        }

        if (steps > 0) {
                val |= steps + 1;
        } else {
                val |= RS5C372_TRIM_DECR;
                val |= (~(-steps - 1)) & 0x3F;
        }

        if (!steps || !(val & 0x3E)) {
                /*
                 * if offset is too small, set oscillation adjustment register
                 * or time trimming register with its default value whic means
                 * no increment or decrement. But for rs5c372[a|b], the XSL bit
                 * should be kept unchanged.
                 */
                if (rs5c->type == rtc_rs5c372a || rs5c->type == rtc_rs5c372b)
                        val &= RS5C372_TRIM_XSL;
                else
                        val = 0;
        }

        dev_dbg(&rs5c->client->dev, "write 0x%x for offset %ld\n", val, offset);

        if (i2c_smbus_write_byte_data(rs5c->client, addr, val) < 0) {
                dev_err(&rs5c->client->dev, "failed to write 0x%x to reg %d\n", val, addr);
                return -EIO;
        }

        rs5c->regs[RS5C372_REG_TRIM] = val;

        return 0;
}

static const struct rtc_class_ops rs5c372_rtc_ops = {
        .proc           = rs5c372_rtc_proc,
        .read_time      = rs5c372_rtc_read_time,
        .set_time       = rs5c372_rtc_set_time,
        .read_alarm     = rs5c_read_alarm,
        .set_alarm      = rs5c_set_alarm,
        .alarm_irq_enable = rs5c_rtc_alarm_irq_enable,
        .ioctl          = rs5c372_ioctl,
        .read_offset    = rs5c372_read_offset,
        .set_offset     = rs5c372_set_offset,
};

#if IS_ENABLED(CONFIG_RTC_INTF_SYSFS)

static ssize_t rs5c372_sysfs_show_trim(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        int err, trim;

        err = rs5c372_get_trim(to_i2c_client(dev), NULL, &trim);
        if (err)
                return err;

        return sprintf(buf, "%d\n", trim);
}
static DEVICE_ATTR(trim, S_IRUGO, rs5c372_sysfs_show_trim, NULL);

static ssize_t rs5c372_sysfs_show_osc(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        int err, osc;

        err = rs5c372_get_trim(to_i2c_client(dev), &osc, NULL);
        if (err)
                return err;

        return sprintf(buf, "%d.%03d KHz\n", osc / 1000, osc % 1000);
}
static DEVICE_ATTR(osc, S_IRUGO, rs5c372_sysfs_show_osc, NULL);

static int rs5c_sysfs_register(struct device *dev)
{
        int err;

        err = device_create_file(dev, &dev_attr_trim);
        if (err)
                return err;
        err = device_create_file(dev, &dev_attr_osc);
        if (err)
                device_remove_file(dev, &dev_attr_trim);

        return err;
}

static void rs5c_sysfs_unregister(struct device *dev)
{
        device_remove_file(dev, &dev_attr_trim);
        device_remove_file(dev, &dev_attr_osc);
}

#else
static int rs5c_sysfs_register(struct device *dev)
{
        return 0;
}

static void rs5c_sysfs_unregister(struct device *dev)
{
        /* nothing */
}
#endif  /* SYSFS */

static struct i2c_driver rs5c372_driver;

static int rs5c_oscillator_setup(struct rs5c372 *rs5c372)
{
        unsigned char buf[2];
        int addr, i, ret = 0;

        addr   = RS5C_ADDR(RS5C_REG_CTRL1);
        buf[0] = rs5c372->regs[RS5C_REG_CTRL1];
        buf[1] = rs5c372->regs[RS5C_REG_CTRL2];

        switch (rs5c372->type) {
        case rtc_r2025sd:
                if (buf[1] & R2x2x_CTRL2_XSTP)
                        return ret;
                break;
        case rtc_r2221tl:
                if (!(buf[1] & R2x2x_CTRL2_XSTP))
                        return ret;
                break;
        default:
                if (!(buf[1] & RS5C_CTRL2_XSTP))
                        return ret;
                break;
        }

        /* use 24hr mode */
        switch (rs5c372->type) {
        case rtc_rs5c372a:
        case rtc_rs5c372b:
                buf[1] |= RS5C372_CTRL2_24;
                rs5c372->time24 = 1;
                break;
        case rtc_r2025sd:
        case rtc_r2221tl:
        case rtc_rv5c386:
        case rtc_rv5c387a:
                buf[0] |= RV5C387_CTRL1_24;
                rs5c372->time24 = 1;
                break;
        default:
                /* impossible */
                break;
        }

        for (i = 0; i < sizeof(buf); i++) {
                addr = RS5C_ADDR(RS5C_REG_CTRL1 + i);
                ret = i2c_smbus_write_byte_data(rs5c372->client, addr, buf[i]);
                if (unlikely(ret < 0))
                        return ret;
        }

        rs5c372->regs[RS5C_REG_CTRL1] = buf[0];
        rs5c372->regs[RS5C_REG_CTRL2] = buf[1];

        return 0;
}

static int rs5c372_probe(struct i2c_client *client)
{
        int err = 0;
        int smbus_mode = 0;
        struct rs5c372 *rs5c372;

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

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
                        I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK)) {
                /*
                 * If we don't have any master mode adapter, try breaking
                 * it down in to the barest of capabilities.
                 */
                if (i2c_check_functionality(client->adapter,
                                I2C_FUNC_SMBUS_BYTE_DATA |
                                I2C_FUNC_SMBUS_I2C_BLOCK))
                        smbus_mode = 1;
                else {
                        /* Still no good, give up */
                        err = -ENODEV;
                        goto exit;
                }
        }

        rs5c372 = devm_kzalloc(&client->dev, sizeof(struct rs5c372),
                                GFP_KERNEL);
        if (!rs5c372) {
                err = -ENOMEM;
                goto exit;
        }

        rs5c372->client = client;
        i2c_set_clientdata(client, rs5c372);
        if (client->dev.of_node) {
                rs5c372->type = (uintptr_t)of_device_get_match_data(&client->dev);
        } else {
                const struct i2c_device_id *id = i2c_match_id(rs5c372_id, client);
                rs5c372->type = id->driver_data;
        }

        /* we read registers 0x0f then 0x00-0x0f; skip the first one */
        rs5c372->regs = &rs5c372->buf[1];
        rs5c372->smbus = smbus_mode;

        err = rs5c_get_regs(rs5c372);
        if (err < 0)
                goto exit;

        /* clock may be set for am/pm or 24 hr time */
        switch (rs5c372->type) {
        case rtc_rs5c372a:
        case rtc_rs5c372b:
                /* alarm uses ALARM_A; and nINTRA on 372a, nINTR on 372b.
                 * so does periodic irq, except some 327a modes.
                 */
                if (rs5c372->regs[RS5C_REG_CTRL2] & RS5C372_CTRL2_24)
                        rs5c372->time24 = 1;
                break;
        case rtc_r2025sd:
        case rtc_r2221tl:
        case rtc_rv5c386:
        case rtc_rv5c387a:
                if (rs5c372->regs[RS5C_REG_CTRL1] & RV5C387_CTRL1_24)
                        rs5c372->time24 = 1;
                /* alarm uses ALARM_W; and nINTRB for alarm and periodic
                 * irq, on both 386 and 387
                 */
                break;
        default:
                dev_err(&client->dev, "unknown RTC type\n");
                goto exit;
        }

        /* if the oscillator lost power and no other software (like
         * the bootloader) set it up, do it here.
         *
         * The R2025S/D does this a little differently than the other
         * parts, so we special case that..
         */
        err = rs5c_oscillator_setup(rs5c372);
        if (unlikely(err < 0)) {
                dev_err(&client->dev, "setup error\n");
                goto exit;
        }

        dev_info(&client->dev, "%s found, %s\n",
                        ({ char *s; switch (rs5c372->type) {
                        case rtc_r2025sd:       s = "r2025sd"; break;
                        case rtc_r2221tl:       s = "r2221tl"; break;
                        case rtc_rs5c372a:      s = "rs5c372a"; break;
                        case rtc_rs5c372b:      s = "rs5c372b"; break;
                        case rtc_rv5c386:       s = "rv5c386"; break;
                        case rtc_rv5c387a:      s = "rv5c387a"; break;
                        default:                s = "chip"; break;
                        }; s;}),
                        rs5c372->time24 ? "24hr" : "am/pm"
                        );

        /* REVISIT use client->irq to register alarm irq ... */
        rs5c372->rtc = devm_rtc_device_register(&client->dev,
                                        rs5c372_driver.driver.name,
                                        &rs5c372_rtc_ops, THIS_MODULE);

        if (IS_ERR(rs5c372->rtc)) {
                err = PTR_ERR(rs5c372->rtc);
                goto exit;
        }

        err = rs5c_sysfs_register(&client->dev);
        if (err)
                goto exit;

        return 0;

exit:
        return err;
}

static void rs5c372_remove(struct i2c_client *client)
{
        rs5c_sysfs_unregister(&client->dev);
}

static struct i2c_driver rs5c372_driver = {
        .driver         = {
                .name   = "rtc-rs5c372",
                .of_match_table = of_match_ptr(rs5c372_of_match),
        },
        .probe          = rs5c372_probe,
        .remove         = rs5c372_remove,
        .id_table       = rs5c372_id,
};

module_i2c_driver(rs5c372_driver);

MODULE_AUTHOR(
                "Pavel Mironchik <pmironchik@optifacio.net>, "
                "Alessandro Zummo <a.zummo@towertech.it>, "
                "Paul Mundt <lethal@linux-sh.org>");
MODULE_DESCRIPTION("Ricoh RS5C372 RTC driver");
MODULE_LICENSE("GPL");