// SPDX-License-Identifier: GPL-2.0-only
/*
 * rtc-ds1307.c - RTC driver for some mostly-compatible I2C chips.
 *
 *  Copyright (C) 2005 James Chapman (ds1337 core)
 *  Copyright (C) 2006 David Brownell
 *  Copyright (C) 2009 Matthias Fuchs (rx8025 support)
 *  Copyright (C) 2012 Bertrand Achard (nvram access fixes)
 */

#include <linux/bcd.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kstrtox.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/property.h>
#include <linux/rtc/ds1307.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/clk-provider.h>
#include <linux/regmap.h>
#include <linux/watchdog.h>

/*
 * We can't determine type by probing, but if we expect pre-Linux code
 * to have set the chip up as a clock (turning on the oscillator and
 * setting the date and time), Linux can ignore the non-clock features.
 * That's a natural job for a factory or repair bench.
 */
enum ds_type {
        unknown_ds_type, /* always first and 0 */
        ds_1307,
        ds_1308,
        ds_1337,
        ds_1338,
        ds_1339,
        ds_1340,
        ds_1341,
        ds_1388,
        ds_3231,
        m41t0,
        m41t00,
        m41t11,
        mcp794xx,
        rx_8025,
        rx_8130,
        last_ds_type /* always last */
        /* rs5c372 too?  different address... */
};

/* RTC registers don't differ much, except for the century flag */
#define DS1307_REG_SECS         0x00    /* 00-59 */
#       define DS1307_BIT_CH            0x80
#       define DS1340_BIT_nEOSC         0x80
#       define MCP794XX_BIT_ST          0x80
#define DS1307_REG_MIN          0x01    /* 00-59 */
#       define M41T0_BIT_OF             0x80
#define DS1307_REG_HOUR         0x02    /* 00-23, or 1-12{am,pm} */
#       define DS1307_BIT_12HR          0x40    /* in REG_HOUR */
#       define DS1307_BIT_PM            0x20    /* in REG_HOUR */
#       define DS1340_BIT_CENTURY_EN    0x80    /* in REG_HOUR */
#       define DS1340_BIT_CENTURY       0x40    /* in REG_HOUR */
#define DS1307_REG_WDAY         0x03    /* 01-07 */
#       define MCP794XX_BIT_OSCRUN      BIT(5)
#       define MCP794XX_BIT_VBATEN      0x08
#define DS1307_REG_MDAY         0x04    /* 01-31 */
#define DS1307_REG_MONTH        0x05    /* 01-12 */
#       define DS1337_BIT_CENTURY       0x80    /* in REG_MONTH */
#define DS1307_REG_YEAR         0x06    /* 00-99 */

/*
 * Other registers (control, status, alarms, trickle charge, NVRAM, etc)
 * start at 7, and they differ a LOT. Only control and status matter for
 * basic RTC date and time functionality; be careful using them.
 */
#define DS1307_REG_CONTROL      0x07            /* or ds1338 */
#       define DS1307_BIT_OUT           0x80
#       define DS1338_BIT_OSF           0x20
#       define DS1307_BIT_SQWE          0x10
#       define DS1307_BIT_RS1           0x02
#       define DS1307_BIT_RS0           0x01
#define DS1337_REG_CONTROL      0x0e
#       define DS1337_BIT_nEOSC         0x80
#       define DS1339_BIT_BBSQI         0x20
#       define DS3231_BIT_BBSQW         0x40 /* same as BBSQI */
#       define DS1337_BIT_RS2           0x10
#       define DS1337_BIT_RS1           0x08
#       define DS1337_BIT_INTCN         0x04
#       define DS1337_BIT_A2IE          0x02
#       define DS1337_BIT_A1IE          0x01
#define DS1340_REG_CONTROL      0x07
#       define DS1340_BIT_OUT           0x80
#       define DS1340_BIT_FT            0x40
#       define DS1340_BIT_CALIB_SIGN    0x20
#       define DS1340_M_CALIBRATION     0x1f
#define DS1340_REG_FLAG         0x09
#       define DS1340_BIT_OSF           0x80
#define DS1337_REG_STATUS       0x0f
#       define DS1337_BIT_OSF           0x80
#       define DS3231_BIT_EN32KHZ       0x08
#       define DS1337_BIT_A2I           0x02
#       define DS1337_BIT_A1I           0x01
#define DS1339_REG_ALARM1_SECS  0x07

#define DS13XX_TRICKLE_CHARGER_MAGIC    0xa0

#define RX8025_REG_CTRL1        0x0e
#       define RX8025_BIT_2412          0x20
#define RX8025_REG_CTRL2        0x0f
#       define RX8025_BIT_PON           0x10
#       define RX8025_BIT_VDET          0x40
#       define RX8025_BIT_XST           0x20

#define RX8130_REG_ALARM_MIN            0x17
#define RX8130_REG_ALARM_HOUR           0x18
#define RX8130_REG_ALARM_WEEK_OR_DAY    0x19
#define RX8130_REG_EXTENSION            0x1c
#define RX8130_REG_EXTENSION_WADA       BIT(3)
#define RX8130_REG_FLAG                 0x1d
#define RX8130_REG_FLAG_VLF             BIT(1)
#define RX8130_REG_FLAG_AF              BIT(3)
#define RX8130_REG_CONTROL0             0x1e
#define RX8130_REG_CONTROL0_AIE         BIT(3)
#define RX8130_REG_CONTROL1             0x1f
#define RX8130_REG_CONTROL1_INIEN       BIT(4)
#define RX8130_REG_CONTROL1_CHGEN       BIT(5)

#define MCP794XX_REG_CONTROL            0x07
#       define MCP794XX_BIT_ALM0_EN     0x10
#       define MCP794XX_BIT_ALM1_EN     0x20
#define MCP794XX_REG_ALARM0_BASE        0x0a
#define MCP794XX_REG_ALARM0_CTRL        0x0d
#define MCP794XX_REG_ALARM1_BASE        0x11
#define MCP794XX_REG_ALARM1_CTRL        0x14
#       define MCP794XX_BIT_ALMX_IF     BIT(3)
#       define MCP794XX_BIT_ALMX_C0     BIT(4)
#       define MCP794XX_BIT_ALMX_C1     BIT(5)
#       define MCP794XX_BIT_ALMX_C2     BIT(6)
#       define MCP794XX_BIT_ALMX_POL    BIT(7)
#       define MCP794XX_MSK_ALMX_MATCH  (MCP794XX_BIT_ALMX_C0 | \
                                         MCP794XX_BIT_ALMX_C1 | \
                                         MCP794XX_BIT_ALMX_C2)

#define M41TXX_REG_CONTROL      0x07
#       define M41TXX_BIT_OUT           BIT(7)
#       define M41TXX_BIT_FT            BIT(6)
#       define M41TXX_BIT_CALIB_SIGN    BIT(5)
#       define M41TXX_M_CALIBRATION     GENMASK(4, 0)

#define DS1388_REG_WDOG_HUN_SECS        0x08
#define DS1388_REG_WDOG_SECS            0x09
#define DS1388_REG_FLAG                 0x0b
#       define DS1388_BIT_WF            BIT(6)
#       define DS1388_BIT_OSF           BIT(7)
#define DS1388_REG_CONTROL              0x0c
#       define DS1388_BIT_RST           BIT(0)
#       define DS1388_BIT_WDE           BIT(1)
#       define DS1388_BIT_nEOSC         BIT(7)

/* negative offset step is -2.034ppm */
#define M41TXX_NEG_OFFSET_STEP_PPB      2034
/* positive offset step is +4.068ppm */
#define M41TXX_POS_OFFSET_STEP_PPB      4068
/* Min and max values supported with 'offset' interface by M41TXX */
#define M41TXX_MIN_OFFSET       ((-31) * M41TXX_NEG_OFFSET_STEP_PPB)
#define M41TXX_MAX_OFFSET       ((31) * M41TXX_POS_OFFSET_STEP_PPB)

struct ds1307 {
        enum ds_type            type;
        struct device           *dev;
        struct regmap           *regmap;
        const char              *name;
        struct rtc_device       *rtc;
#ifdef CONFIG_COMMON_CLK
        struct clk_hw           clks[2];
#endif
};

struct chip_desc {
        unsigned                alarm:1;
        u16                     nvram_offset;
        u16                     nvram_size;
        u8                      offset; /* register's offset */
        u8                      century_reg;
        u8                      century_enable_bit;
        u8                      century_bit;
        u8                      bbsqi_bit;
        irq_handler_t           irq_handler;
        const struct rtc_class_ops *rtc_ops;
        u16                     trickle_charger_reg;
        u8                      (*do_trickle_setup)(struct ds1307 *, u32,
                                                    bool);
        /* Does the RTC require trickle-resistor-ohms to select the value of
         * the resistor between Vcc and Vbackup?
         */
        bool                    requires_trickle_resistor;
        /* Some RTC's batteries and supercaps were charged by default, others
         * allow charging but were not configured previously to do so.
         * Remember this behavior to stay backwards compatible.
         */
        bool                    charge_default;
};

static const struct chip_desc chips[last_ds_type];

static int ds1307_get_time(struct device *dev, struct rtc_time *t)
{
        struct ds1307   *ds1307 = dev_get_drvdata(dev);
        int             tmp, ret;
        const struct chip_desc *chip = &chips[ds1307->type];
        u8 regs[7];

        if (ds1307->type == rx_8130) {
                unsigned int regflag;
                ret = regmap_read(ds1307->regmap, RX8130_REG_FLAG, &regflag);
                if (ret) {
                        dev_err(dev, "%s error %d\n", "read", ret);
                        return ret;
                }

                if (regflag & RX8130_REG_FLAG_VLF) {
                        dev_warn_once(dev, "oscillator failed, set time!\n");
                        return -EINVAL;
                }
        }

        /* read the RTC date and time registers all at once */
        ret = regmap_bulk_read(ds1307->regmap, chip->offset, regs,
                               sizeof(regs));
        if (ret) {
                dev_err(dev, "%s error %d\n", "read", ret);
                return ret;
        }

        dev_dbg(dev, "%s: %7ph\n", "read", regs);

        /* if oscillator fail bit is set, no data can be trusted */
        if (ds1307->type == m41t0 &&
            regs[DS1307_REG_MIN] & M41T0_BIT_OF) {
                dev_warn_once(dev, "oscillator failed, set time!\n");
                return -EINVAL;
        } else if (ds1307->type == mcp794xx &&
            !(regs[DS1307_REG_WDAY] & MCP794XX_BIT_OSCRUN)) {
                dev_warn_once(dev, "oscillator failed, set time!\n");
                return -EINVAL;
        }

        tmp = regs[DS1307_REG_SECS];
        switch (ds1307->type) {
        case ds_1307:
        case m41t0:
        case m41t00:
        case m41t11:
                if (tmp & DS1307_BIT_CH)
                        return -EINVAL;
                break;
        case ds_1308:
        case ds_1338:
                if (tmp & DS1307_BIT_CH)
                        return -EINVAL;

                ret = regmap_read(ds1307->regmap, DS1307_REG_CONTROL, &tmp);
                if (ret)
                        return ret;
                if (tmp & DS1338_BIT_OSF)
                        return -EINVAL;
                break;
        case ds_1340:
                if (tmp & DS1340_BIT_nEOSC)
                        return -EINVAL;

                ret = regmap_read(ds1307->regmap, DS1340_REG_FLAG, &tmp);
                if (ret)
                        return ret;
                if (tmp & DS1340_BIT_OSF)
                        return -EINVAL;
                break;
        case ds_1341:
                ret = regmap_read(ds1307->regmap, DS1337_REG_STATUS, &tmp);
                if (ret)
                        return ret;
                if (tmp & DS1337_BIT_OSF)
                        return -EINVAL;
                break;
        case ds_1388:
                ret = regmap_read(ds1307->regmap, DS1388_REG_FLAG, &tmp);
                if (ret)
                        return ret;
                if (tmp & DS1388_BIT_OSF)
                        return -EINVAL;
                break;
        case mcp794xx:
                if (!(tmp & MCP794XX_BIT_ST))
                        return -EINVAL;

                break;
        default:
                break;
        }

        t->tm_sec = bcd2bin(regs[DS1307_REG_SECS] & 0x7f);
        t->tm_min = bcd2bin(regs[DS1307_REG_MIN] & 0x7f);
        tmp = regs[DS1307_REG_HOUR] & 0x3f;
        t->tm_hour = bcd2bin(tmp);
        /* rx8130 is bit position, not BCD */
        if (ds1307->type == rx_8130)
                t->tm_wday = fls(regs[DS1307_REG_WDAY] & 0x7f);
        else
                t->tm_wday = bcd2bin(regs[DS1307_REG_WDAY] & 0x07) - 1;
        t->tm_mday = bcd2bin(regs[DS1307_REG_MDAY] & 0x3f);
        tmp = regs[DS1307_REG_MONTH] & 0x1f;
        t->tm_mon = bcd2bin(tmp) - 1;
        t->tm_year = bcd2bin(regs[DS1307_REG_YEAR]) + 100;

        if (regs[chip->century_reg] & chip->century_bit &&
            IS_ENABLED(CONFIG_RTC_DRV_DS1307_CENTURY))
                t->tm_year += 100;

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

        return 0;
}

static int ds1307_set_time(struct device *dev, struct rtc_time *t)
{
        struct ds1307   *ds1307 = dev_get_drvdata(dev);
        const struct chip_desc *chip = &chips[ds1307->type];
        int             result;
        int             tmp;
        u8              regs[7];

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

        if (t->tm_year < 100)
                return -EINVAL;

#ifdef CONFIG_RTC_DRV_DS1307_CENTURY
        if (t->tm_year > (chip->century_bit ? 299 : 199))
                return -EINVAL;
#else
        if (t->tm_year > 199)
                return -EINVAL;
#endif

        regs[DS1307_REG_SECS] = bin2bcd(t->tm_sec);
        regs[DS1307_REG_MIN] = bin2bcd(t->tm_min);
        regs[DS1307_REG_HOUR] = bin2bcd(t->tm_hour);
        /* rx8130 is bit position, not BCD */
        if (ds1307->type == rx_8130)
                regs[DS1307_REG_WDAY] = 1 << t->tm_wday;
        else
                regs[DS1307_REG_WDAY] = bin2bcd(t->tm_wday + 1);
        regs[DS1307_REG_MDAY] = bin2bcd(t->tm_mday);
        regs[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);

        /* assume 20YY not 19YY */
        tmp = t->tm_year % 100;
        regs[DS1307_REG_YEAR] = bin2bcd(tmp);

        if (chip->century_enable_bit)
                regs[chip->century_reg] |= chip->century_enable_bit;
        if (t->tm_year > 199 && chip->century_bit)
                regs[chip->century_reg] |= chip->century_bit;

        switch (ds1307->type) {
        case ds_1308:
        case ds_1338:
                regmap_update_bits(ds1307->regmap, DS1307_REG_CONTROL,
                                   DS1338_BIT_OSF, 0);
                break;
        case ds_1340:
                regmap_update_bits(ds1307->regmap, DS1340_REG_FLAG,
                                   DS1340_BIT_OSF, 0);
                break;
        case ds_1341:
                regmap_update_bits(ds1307->regmap, DS1337_REG_STATUS,
                                   DS1337_BIT_OSF, 0);
                break;
        case ds_1388:
                regmap_update_bits(ds1307->regmap, DS1388_REG_FLAG,
                                   DS1388_BIT_OSF, 0);
                break;
        case mcp794xx:
                /*
                 * these bits were cleared when preparing the date/time
                 * values and need to be set again before writing the
                 * regsfer out to the device.
                 */
                regs[DS1307_REG_SECS] |= MCP794XX_BIT_ST;
                regs[DS1307_REG_WDAY] |= MCP794XX_BIT_VBATEN;
                break;
        default:
                break;
        }

        dev_dbg(dev, "%s: %7ph\n", "write", regs);

        result = regmap_bulk_write(ds1307->regmap, chip->offset, regs,
                                   sizeof(regs));
        if (result) {
                dev_err(dev, "%s error %d\n", "write", result);
                return result;
        }

        if (ds1307->type == rx_8130) {
                /* clear Voltage Loss Flag as data is available now */
                result = regmap_write(ds1307->regmap, RX8130_REG_FLAG,
                                      ~(u8)RX8130_REG_FLAG_VLF);
                if (result) {
                        dev_err(dev, "%s error %d\n", "write", result);
                        return result;
                }
        }

        return 0;
}

static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct ds1307           *ds1307 = dev_get_drvdata(dev);
        int                     ret;
        u8                      regs[9];

        /* read all ALARM1, ALARM2, and status registers at once */
        ret = regmap_bulk_read(ds1307->regmap, DS1339_REG_ALARM1_SECS,
                               regs, sizeof(regs));
        if (ret) {
                dev_err(dev, "%s error %d\n", "alarm read", ret);
                return ret;
        }

        dev_dbg(dev, "%s: %4ph, %3ph, %2ph\n", "alarm read",
                &regs[0], &regs[4], &regs[7]);

        /*
         * report alarm time (ALARM1); assume 24 hour and day-of-month modes,
         * and that all four fields are checked matches
         */
        t->time.tm_sec = bcd2bin(regs[0] & 0x7f);
        t->time.tm_min = bcd2bin(regs[1] & 0x7f);
        t->time.tm_hour = bcd2bin(regs[2] & 0x3f);
        t->time.tm_mday = bcd2bin(regs[3] & 0x3f);

        /* ... and status */
        t->enabled = !!(regs[7] & DS1337_BIT_A1IE);
        t->pending = !!(regs[8] & DS1337_BIT_A1I);

        dev_dbg(dev, "%s secs=%d, mins=%d, "
                "hours=%d, mday=%d, enabled=%d, pending=%d\n",
                "alarm read", t->time.tm_sec, t->time.tm_min,
                t->time.tm_hour, t->time.tm_mday,
                t->enabled, t->pending);

        return 0;
}

static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct ds1307           *ds1307 = dev_get_drvdata(dev);
        unsigned char           regs[9];
        u8                      control, status;
        int                     ret;

        dev_dbg(dev, "%s secs=%d, mins=%d, "
                "hours=%d, mday=%d, enabled=%d, pending=%d\n",
                "alarm set", t->time.tm_sec, t->time.tm_min,
                t->time.tm_hour, t->time.tm_mday,
                t->enabled, t->pending);

        /* read current status of both alarms and the chip */
        ret = regmap_bulk_read(ds1307->regmap, DS1339_REG_ALARM1_SECS, regs,
                               sizeof(regs));
        if (ret) {
                dev_err(dev, "%s error %d\n", "alarm write", ret);
                return ret;
        }
        control = regs[7];
        status = regs[8];

        dev_dbg(dev, "%s: %4ph, %3ph, %02x %02x\n", "alarm set (old status)",
                &regs[0], &regs[4], control, status);

        /* set ALARM1, using 24 hour and day-of-month modes */
        regs[0] = bin2bcd(t->time.tm_sec);
        regs[1] = bin2bcd(t->time.tm_min);
        regs[2] = bin2bcd(t->time.tm_hour);
        regs[3] = bin2bcd(t->time.tm_mday);

        /* set ALARM2 to non-garbage */
        regs[4] = 0;
        regs[5] = 0;
        regs[6] = 0;

        /* disable alarms */
        regs[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
        regs[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);

        ret = regmap_bulk_write(ds1307->regmap, DS1339_REG_ALARM1_SECS, regs,
                                sizeof(regs));
        if (ret) {
                dev_err(dev, "can't set alarm time\n");
                return ret;
        }

        /* optionally enable ALARM1 */
        if (t->enabled) {
                dev_dbg(dev, "alarm IRQ armed\n");
                regs[7] |= DS1337_BIT_A1IE;     /* only ALARM1 is used */
                regmap_write(ds1307->regmap, DS1337_REG_CONTROL, regs[7]);
        }

        return 0;
}

static int ds1307_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct ds1307           *ds1307 = dev_get_drvdata(dev);

        return regmap_update_bits(ds1307->regmap, DS1337_REG_CONTROL,
                                  DS1337_BIT_A1IE,
                                  enabled ? DS1337_BIT_A1IE : 0);
}

static u8 do_trickle_setup_ds1339(struct ds1307 *ds1307, u32 ohms, bool diode)
{
        u8 setup = (diode) ? DS1307_TRICKLE_CHARGER_DIODE :
                DS1307_TRICKLE_CHARGER_NO_DIODE;

        setup |= DS13XX_TRICKLE_CHARGER_MAGIC;

        switch (ohms) {
        case 250:
                setup |= DS1307_TRICKLE_CHARGER_250_OHM;
                break;
        case 2000:
                setup |= DS1307_TRICKLE_CHARGER_2K_OHM;
                break;
        case 4000:
                setup |= DS1307_TRICKLE_CHARGER_4K_OHM;
                break;
        default:
                dev_warn(ds1307->dev,
                         "Unsupported ohm value %u in dt\n", ohms);
                return 0;
        }
        return setup;
}

static u8 do_trickle_setup_rx8130(struct ds1307 *ds1307, u32 ohms, bool diode)
{
        /* make sure that the backup battery is enabled */
        u8 setup = RX8130_REG_CONTROL1_INIEN;
        if (diode)
                setup |= RX8130_REG_CONTROL1_CHGEN;

        return setup;
}

static irqreturn_t rx8130_irq(int irq, void *dev_id)
{
        struct ds1307           *ds1307 = dev_id;
        u8 ctl[3];
        int ret;

        rtc_lock(ds1307->rtc);

        /* Read control registers. */
        ret = regmap_bulk_read(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
                               sizeof(ctl));
        if (ret < 0)
                goto out;
        if (!(ctl[1] & RX8130_REG_FLAG_AF))
                goto out;
        ctl[1] &= ~RX8130_REG_FLAG_AF;
        ctl[2] &= ~RX8130_REG_CONTROL0_AIE;

        ret = regmap_bulk_write(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
                                sizeof(ctl));
        if (ret < 0)
                goto out;

        rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);

out:
        rtc_unlock(ds1307->rtc);

        return IRQ_HANDLED;
}

static int rx8130_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);
        u8 ald[3], ctl[3];
        int ret;

        /* Read alarm registers. */
        ret = regmap_bulk_read(ds1307->regmap, RX8130_REG_ALARM_MIN, ald,
                               sizeof(ald));
        if (ret < 0)
                return ret;

        /* Read control registers. */
        ret = regmap_bulk_read(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
                               sizeof(ctl));
        if (ret < 0)
                return ret;

        t->enabled = !!(ctl[2] & RX8130_REG_CONTROL0_AIE);
        t->pending = !!(ctl[1] & RX8130_REG_FLAG_AF);

        /* Report alarm 0 time assuming 24-hour and day-of-month modes. */
        t->time.tm_sec = -1;
        t->time.tm_min = bcd2bin(ald[0] & 0x7f);
        t->time.tm_hour = bcd2bin(ald[1] & 0x7f);
        t->time.tm_wday = -1;
        t->time.tm_mday = bcd2bin(ald[2] & 0x7f);
        t->time.tm_mon = -1;
        t->time.tm_year = -1;
        t->time.tm_yday = -1;
        t->time.tm_isdst = -1;

        dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d enabled=%d\n",
                __func__, t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
                t->time.tm_wday, t->time.tm_mday, t->time.tm_mon, t->enabled);

        return 0;
}

static int rx8130_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);
        u8 ald[3], ctl[3];
        int ret;

        dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
                "enabled=%d pending=%d\n", __func__,
                t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
                t->time.tm_wday, t->time.tm_mday, t->time.tm_mon,
                t->enabled, t->pending);

        /* Read control registers. */
        ret = regmap_bulk_read(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
                               sizeof(ctl));
        if (ret < 0)
                return ret;

        ctl[0] &= RX8130_REG_EXTENSION_WADA;
        ctl[1] &= ~RX8130_REG_FLAG_AF;
        ctl[2] &= ~RX8130_REG_CONTROL0_AIE;

        ret = regmap_bulk_write(ds1307->regmap, RX8130_REG_EXTENSION, ctl,
                                sizeof(ctl));
        if (ret < 0)
                return ret;

        /* Hardware alarm precision is 1 minute! */
        ald[0] = bin2bcd(t->time.tm_min);
        ald[1] = bin2bcd(t->time.tm_hour);
        ald[2] = bin2bcd(t->time.tm_mday);

        ret = regmap_bulk_write(ds1307->regmap, RX8130_REG_ALARM_MIN, ald,
                                sizeof(ald));
        if (ret < 0)
                return ret;

        if (!t->enabled)
                return 0;

        ctl[2] |= RX8130_REG_CONTROL0_AIE;

        return regmap_write(ds1307->regmap, RX8130_REG_CONTROL0, ctl[2]);
}

static int rx8130_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);
        int ret, reg;

        ret = regmap_read(ds1307->regmap, RX8130_REG_CONTROL0, &reg);
        if (ret < 0)
                return ret;

        if (enabled)
                reg |= RX8130_REG_CONTROL0_AIE;
        else
                reg &= ~RX8130_REG_CONTROL0_AIE;

        return regmap_write(ds1307->regmap, RX8130_REG_CONTROL0, reg);
}

static irqreturn_t mcp794xx_irq(int irq, void *dev_id)
{
        struct ds1307           *ds1307 = dev_id;
        struct mutex            *lock = &ds1307->rtc->ops_lock;
        int reg, ret;

        mutex_lock(lock);

        /* Check and clear alarm 0 interrupt flag. */
        ret = regmap_read(ds1307->regmap, MCP794XX_REG_ALARM0_CTRL, &reg);
        if (ret)
                goto out;
        if (!(reg & MCP794XX_BIT_ALMX_IF))
                goto out;
        reg &= ~MCP794XX_BIT_ALMX_IF;
        ret = regmap_write(ds1307->regmap, MCP794XX_REG_ALARM0_CTRL, reg);
        if (ret)
                goto out;

        /* Disable alarm 0. */
        ret = regmap_update_bits(ds1307->regmap, MCP794XX_REG_CONTROL,
                                 MCP794XX_BIT_ALM0_EN, 0);
        if (ret)
                goto out;

        rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);

out:
        mutex_unlock(lock);

        return IRQ_HANDLED;
}

static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);
        u8 regs[10];
        int ret;

        /* Read control and alarm 0 registers. */
        ret = regmap_bulk_read(ds1307->regmap, MCP794XX_REG_CONTROL, regs,
                               sizeof(regs));
        if (ret)
                return ret;

        t->enabled = !!(regs[0] & MCP794XX_BIT_ALM0_EN);

        /* Report alarm 0 time assuming 24-hour and day-of-month modes. */
        t->time.tm_sec = bcd2bin(regs[3] & 0x7f);
        t->time.tm_min = bcd2bin(regs[4] & 0x7f);
        t->time.tm_hour = bcd2bin(regs[5] & 0x3f);
        t->time.tm_wday = bcd2bin(regs[6] & 0x7) - 1;
        t->time.tm_mday = bcd2bin(regs[7] & 0x3f);
        t->time.tm_mon = bcd2bin(regs[8] & 0x1f) - 1;
        t->time.tm_year = -1;
        t->time.tm_yday = -1;
        t->time.tm_isdst = -1;

        dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
                "enabled=%d polarity=%d irq=%d match=%lu\n", __func__,
                t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
                t->time.tm_wday, t->time.tm_mday, t->time.tm_mon, t->enabled,
                !!(regs[6] & MCP794XX_BIT_ALMX_POL),
                !!(regs[6] & MCP794XX_BIT_ALMX_IF),
                (regs[6] & MCP794XX_MSK_ALMX_MATCH) >> 4);

        return 0;
}

/*
 * We may have a random RTC weekday, therefore calculate alarm weekday based
 * on current weekday we read from the RTC timekeeping regs
 */
static int mcp794xx_alm_weekday(struct device *dev, struct rtc_time *tm_alarm)
{
        struct rtc_time tm_now;
        int days_now, days_alarm, ret;

        ret = ds1307_get_time(dev, &tm_now);
        if (ret)
                return ret;

        days_now = div_s64(rtc_tm_to_time64(&tm_now), 24 * 60 * 60);
        days_alarm = div_s64(rtc_tm_to_time64(tm_alarm), 24 * 60 * 60);

        return (tm_now.tm_wday + days_alarm - days_now) % 7 + 1;
}

static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);
        unsigned char regs[10];
        int wday, ret;

        wday = mcp794xx_alm_weekday(dev, &t->time);
        if (wday < 0)
                return wday;

        dev_dbg(dev, "%s, sec=%d min=%d hour=%d wday=%d mday=%d mon=%d "
                "enabled=%d pending=%d\n", __func__,
                t->time.tm_sec, t->time.tm_min, t->time.tm_hour,
                t->time.tm_wday, t->time.tm_mday, t->time.tm_mon,
                t->enabled, t->pending);

        /* Read control and alarm 0 registers. */
        ret = regmap_bulk_read(ds1307->regmap, MCP794XX_REG_CONTROL, regs,
                               sizeof(regs));
        if (ret)
                return ret;

        /* Set alarm 0, using 24-hour and day-of-month modes. */
        regs[3] = bin2bcd(t->time.tm_sec);
        regs[4] = bin2bcd(t->time.tm_min);
        regs[5] = bin2bcd(t->time.tm_hour);
        regs[6] = wday;
        regs[7] = bin2bcd(t->time.tm_mday);
        regs[8] = bin2bcd(t->time.tm_mon + 1);

        /* Clear the alarm 0 interrupt flag. */
        regs[6] &= ~MCP794XX_BIT_ALMX_IF;
        /* Set alarm match: second, minute, hour, day, date, month. */
        regs[6] |= MCP794XX_MSK_ALMX_MATCH;
        /* Disable interrupt. We will not enable until completely programmed */
        regs[0] &= ~MCP794XX_BIT_ALM0_EN;

        ret = regmap_bulk_write(ds1307->regmap, MCP794XX_REG_CONTROL, regs,
                                sizeof(regs));
        if (ret)
                return ret;

        if (!t->enabled)
                return 0;
        regs[0] |= MCP794XX_BIT_ALM0_EN;
        return regmap_write(ds1307->regmap, MCP794XX_REG_CONTROL, regs[0]);
}

static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);

        return regmap_update_bits(ds1307->regmap, MCP794XX_REG_CONTROL,
                                  MCP794XX_BIT_ALM0_EN,
                                  enabled ? MCP794XX_BIT_ALM0_EN : 0);
}

static int m41txx_rtc_read_offset(struct device *dev, long *offset)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);
        unsigned int ctrl_reg;
        u8 val;

        regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);

        val = ctrl_reg & M41TXX_M_CALIBRATION;

        /* check if positive */
        if (ctrl_reg & M41TXX_BIT_CALIB_SIGN)
                *offset = (val * M41TXX_POS_OFFSET_STEP_PPB);
        else
                *offset = -(val * M41TXX_NEG_OFFSET_STEP_PPB);

        return 0;
}

static int m41txx_rtc_set_offset(struct device *dev, long offset)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);
        unsigned int ctrl_reg;

        if ((offset < M41TXX_MIN_OFFSET) || (offset > M41TXX_MAX_OFFSET))
                return -ERANGE;

        if (offset >= 0) {
                ctrl_reg = DIV_ROUND_CLOSEST(offset,
                                             M41TXX_POS_OFFSET_STEP_PPB);
                ctrl_reg |= M41TXX_BIT_CALIB_SIGN;
        } else {
                ctrl_reg = DIV_ROUND_CLOSEST(abs(offset),
                                             M41TXX_NEG_OFFSET_STEP_PPB);
        }

        return regmap_update_bits(ds1307->regmap, M41TXX_REG_CONTROL,
                                  M41TXX_M_CALIBRATION | M41TXX_BIT_CALIB_SIGN,
                                  ctrl_reg);
}

#ifdef CONFIG_WATCHDOG_CORE
static int ds1388_wdt_start(struct watchdog_device *wdt_dev)
{
        struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);
        u8 regs[2];
        int ret;

        ret = regmap_update_bits(ds1307->regmap, DS1388_REG_FLAG,
                                 DS1388_BIT_WF, 0);
        if (ret)
                return ret;

        ret = regmap_update_bits(ds1307->regmap, DS1388_REG_CONTROL,
                                 DS1388_BIT_WDE | DS1388_BIT_RST, 0);
        if (ret)
                return ret;

        /*
         * watchdog timeouts are measured in seconds. So ignore hundredths of
         * seconds field.
         */
        regs[0] = 0;
        regs[1] = bin2bcd(wdt_dev->timeout);

        ret = regmap_bulk_write(ds1307->regmap, DS1388_REG_WDOG_HUN_SECS, regs,
                                sizeof(regs));
        if (ret)
                return ret;

        return regmap_update_bits(ds1307->regmap, DS1388_REG_CONTROL,
                                  DS1388_BIT_WDE | DS1388_BIT_RST,
                                  DS1388_BIT_WDE | DS1388_BIT_RST);
}

static int ds1388_wdt_stop(struct watchdog_device *wdt_dev)
{
        struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);

        return regmap_update_bits(ds1307->regmap, DS1388_REG_CONTROL,
                                  DS1388_BIT_WDE | DS1388_BIT_RST, 0);
}

static int ds1388_wdt_ping(struct watchdog_device *wdt_dev)
{
        struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);
        u8 regs[2];

        return regmap_bulk_read(ds1307->regmap, DS1388_REG_WDOG_HUN_SECS, regs,
                                sizeof(regs));
}

static int ds1388_wdt_set_timeout(struct watchdog_device *wdt_dev,
                                  unsigned int val)
{
        struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);
        u8 regs[2];

        wdt_dev->timeout = val;
        regs[0] = 0;
        regs[1] = bin2bcd(wdt_dev->timeout);

        return regmap_bulk_write(ds1307->regmap, DS1388_REG_WDOG_HUN_SECS, regs,
                                 sizeof(regs));
}
#endif

static const struct rtc_class_ops rx8130_rtc_ops = {
        .read_time      = ds1307_get_time,
        .set_time       = ds1307_set_time,
        .read_alarm     = rx8130_read_alarm,
        .set_alarm      = rx8130_set_alarm,
        .alarm_irq_enable = rx8130_alarm_irq_enable,
};

static const struct rtc_class_ops mcp794xx_rtc_ops = {
        .read_time      = ds1307_get_time,
        .set_time       = ds1307_set_time,
        .read_alarm     = mcp794xx_read_alarm,
        .set_alarm      = mcp794xx_set_alarm,
        .alarm_irq_enable = mcp794xx_alarm_irq_enable,
};

static const struct rtc_class_ops m41txx_rtc_ops = {
        .read_time      = ds1307_get_time,
        .set_time       = ds1307_set_time,
        .read_alarm     = ds1337_read_alarm,
        .set_alarm      = ds1337_set_alarm,
        .alarm_irq_enable = ds1307_alarm_irq_enable,
        .read_offset    = m41txx_rtc_read_offset,
        .set_offset     = m41txx_rtc_set_offset,
};

static const struct chip_desc chips[last_ds_type] = {
        [ds_1307] = {
                .nvram_offset   = 8,
                .nvram_size     = 56,
        },
        [ds_1308] = {
                .nvram_offset   = 8,
                .nvram_size     = 56,
        },
        [ds_1337] = {
                .alarm          = 1,
                .century_reg    = DS1307_REG_MONTH,
                .century_bit    = DS1337_BIT_CENTURY,
        },
        [ds_1338] = {
                .nvram_offset   = 8,
                .nvram_size     = 56,
        },
        [ds_1339] = {
                .alarm          = 1,
                .century_reg    = DS1307_REG_MONTH,
                .century_bit    = DS1337_BIT_CENTURY,
                .bbsqi_bit      = DS1339_BIT_BBSQI,
                .trickle_charger_reg = 0x10,
                .do_trickle_setup = &do_trickle_setup_ds1339,
                .requires_trickle_resistor = true,
                .charge_default = true,
        },
        [ds_1340] = {
                .century_reg    = DS1307_REG_HOUR,
                .century_enable_bit = DS1340_BIT_CENTURY_EN,
                .century_bit    = DS1340_BIT_CENTURY,
                .do_trickle_setup = &do_trickle_setup_ds1339,
                .trickle_charger_reg = 0x08,
                .requires_trickle_resistor = true,
                .charge_default = true,
        },
        [ds_1341] = {
                .century_reg    = DS1307_REG_MONTH,
                .century_bit    = DS1337_BIT_CENTURY,
        },
        [ds_1388] = {
                .offset         = 1,
                .trickle_charger_reg = 0x0a,
        },
        [ds_3231] = {
                .alarm          = 1,
                .century_reg    = DS1307_REG_MONTH,
                .century_bit    = DS1337_BIT_CENTURY,
                .bbsqi_bit      = DS3231_BIT_BBSQW,
        },
        [rx_8130] = {
                .alarm          = 1,
                /* this is battery backed SRAM */
                .nvram_offset   = 0x20,
                .nvram_size     = 4,    /* 32bit (4 word x 8 bit) */
                .offset         = 0x10,
                .irq_handler = rx8130_irq,
                .rtc_ops = &rx8130_rtc_ops,
                .trickle_charger_reg = RX8130_REG_CONTROL1,
                .do_trickle_setup = &do_trickle_setup_rx8130,
        },
        [m41t0] = {
                .rtc_ops        = &m41txx_rtc_ops,
        },
        [m41t00] = {
                .rtc_ops        = &m41txx_rtc_ops,
        },
        [m41t11] = {
                /* this is battery backed SRAM */
                .nvram_offset   = 8,
                .nvram_size     = 56,
                .rtc_ops        = &m41txx_rtc_ops,
        },
        [mcp794xx] = {
                .alarm          = 1,
                /* this is battery backed SRAM */
                .nvram_offset   = 0x20,
                .nvram_size     = 0x40,
                .irq_handler = mcp794xx_irq,
                .rtc_ops = &mcp794xx_rtc_ops,
        },
};

static const struct i2c_device_id ds1307_id[] = {
        { "ds1307", ds_1307 },
        { "ds1308", ds_1308 },
        { "ds1337", ds_1337 },
        { "ds1338", ds_1338 },
        { "ds1339", ds_1339 },
        { "ds1388", ds_1388 },
        { "ds1340", ds_1340 },
        { "ds1341", ds_1341 },
        { "ds3231", ds_3231 },
        { "m41t0", m41t0 },
        { "m41t00", m41t00 },
        { "m41t11", m41t11 },
        { "mcp7940x", mcp794xx },
        { "mcp7941x", mcp794xx },
        { "pt7c4338", ds_1307 },
        { "rx8025", rx_8025 },
        { "isl12057", ds_1337 },
        { "rx8130", rx_8130 },
        { }
};
MODULE_DEVICE_TABLE(i2c, ds1307_id);

static const struct of_device_id ds1307_of_match[] = {
        {
                .compatible = "dallas,ds1307",
                .data = (void *)ds_1307
        },
        {
                .compatible = "dallas,ds1308",
                .data = (void *)ds_1308
        },
        {
                .compatible = "dallas,ds1337",
                .data = (void *)ds_1337
        },
        {
                .compatible = "dallas,ds1338",
                .data = (void *)ds_1338
        },
        {
                .compatible = "dallas,ds1339",
                .data = (void *)ds_1339
        },
        {
                .compatible = "dallas,ds1388",
                .data = (void *)ds_1388
        },
        {
                .compatible = "dallas,ds1340",
                .data = (void *)ds_1340
        },
        {
                .compatible = "dallas,ds1341",
                .data = (void *)ds_1341
        },
        {
                .compatible = "maxim,ds3231",
                .data = (void *)ds_3231
        },
        {
                .compatible = "st,m41t0",
                .data = (void *)m41t0
        },
        {
                .compatible = "st,m41t00",
                .data = (void *)m41t00
        },
        {
                .compatible = "st,m41t11",
                .data = (void *)m41t11
        },
        {
                .compatible = "microchip,mcp7940x",
                .data = (void *)mcp794xx
        },
        {
                .compatible = "microchip,mcp7941x",
                .data = (void *)mcp794xx
        },
        {
                .compatible = "pericom,pt7c4338",
                .data = (void *)ds_1307
        },
        {
                .compatible = "epson,rx8025",
                .data = (void *)rx_8025
        },
        {
                .compatible = "isil,isl12057",
                .data = (void *)ds_1337
        },
        {
                .compatible = "epson,rx8130",
                .data = (void *)rx_8130
        },
        { }
};
MODULE_DEVICE_TABLE(of, ds1307_of_match);

/*
 * The ds1337 and ds1339 both have two alarms, but we only use the first
 * one (with a "seconds" field).  For ds1337 we expect nINTA is our alarm
 * signal; ds1339 chips have only one alarm signal.
 */
static irqreturn_t ds1307_irq(int irq, void *dev_id)
{
        struct ds1307           *ds1307 = dev_id;
        struct mutex            *lock = &ds1307->rtc->ops_lock;
        int                     stat, ret;

        mutex_lock(lock);
        ret = regmap_read(ds1307->regmap, DS1337_REG_STATUS, &stat);
        if (ret)
                goto out;

        if (stat & DS1337_BIT_A1I) {
                stat &= ~DS1337_BIT_A1I;
                regmap_write(ds1307->regmap, DS1337_REG_STATUS, stat);

                ret = regmap_update_bits(ds1307->regmap, DS1337_REG_CONTROL,
                                         DS1337_BIT_A1IE, 0);
                if (ret)
                        goto out;

                rtc_update_irq(ds1307->rtc, 1, RTC_AF | RTC_IRQF);
        }

out:
        mutex_unlock(lock);

        return IRQ_HANDLED;
}

/*----------------------------------------------------------------------*/

static const struct rtc_class_ops ds13xx_rtc_ops = {
        .read_time      = ds1307_get_time,
        .set_time       = ds1307_set_time,
        .read_alarm     = ds1337_read_alarm,
        .set_alarm      = ds1337_set_alarm,
        .alarm_irq_enable = ds1307_alarm_irq_enable,
};

static ssize_t frequency_test_store(struct device *dev,
                                    struct device_attribute *attr,
                                    const char *buf, size_t count)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev->parent);
        bool freq_test_en;
        int ret;

        ret = kstrtobool(buf, &freq_test_en);
        if (ret) {
                dev_err(dev, "Failed to store RTC Frequency Test attribute\n");
                return ret;
        }

        regmap_update_bits(ds1307->regmap, M41TXX_REG_CONTROL, M41TXX_BIT_FT,
                           freq_test_en ? M41TXX_BIT_FT : 0);

        return count;
}

static ssize_t frequency_test_show(struct device *dev,
                                   struct device_attribute *attr,
                                   char *buf)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev->parent);
        unsigned int ctrl_reg;

        regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);

        return sysfs_emit(buf, (ctrl_reg & M41TXX_BIT_FT) ? "on\n" : "off\n");
}

static DEVICE_ATTR_RW(frequency_test);

static struct attribute *rtc_freq_test_attrs[] = {
        &dev_attr_frequency_test.attr,
        NULL,
};

static const struct attribute_group rtc_freq_test_attr_group = {
        .attrs          = rtc_freq_test_attrs,
};

static int ds1307_add_frequency_test(struct ds1307 *ds1307)
{
        int err;

        switch (ds1307->type) {
        case m41t0:
        case m41t00:
        case m41t11:
                err = rtc_add_group(ds1307->rtc, &rtc_freq_test_attr_group);
                if (err)
                        return err;
                break;
        default:
                break;
        }

        return 0;
}

/*----------------------------------------------------------------------*/

static int ds1307_nvram_read(void *priv, unsigned int offset, void *val,
                             size_t bytes)
{
        struct ds1307 *ds1307 = priv;
        const struct chip_desc *chip = &chips[ds1307->type];

        return regmap_bulk_read(ds1307->regmap, chip->nvram_offset + offset,
                                val, bytes);
}

static int ds1307_nvram_write(void *priv, unsigned int offset, void *val,
                              size_t bytes)
{
        struct ds1307 *ds1307 = priv;
        const struct chip_desc *chip = &chips[ds1307->type];

        return regmap_bulk_write(ds1307->regmap, chip->nvram_offset + offset,
                                 val, bytes);
}

/*----------------------------------------------------------------------*/

static u8 ds1307_trickle_init(struct ds1307 *ds1307,
                              const struct chip_desc *chip)
{
        u32 ohms, chargeable;
        bool diode = chip->charge_default;

        if (!chip->do_trickle_setup)
                return 0;

        if (device_property_read_u32(ds1307->dev, "trickle-resistor-ohms",
                                     &ohms) && chip->requires_trickle_resistor)
                return 0;

        /* aux-voltage-chargeable takes precedence over the deprecated
         * trickle-diode-disable
         */
        if (!device_property_read_u32(ds1307->dev, "aux-voltage-chargeable",
                                     &chargeable)) {
                switch (chargeable) {
                case 0:
                        diode = false;
                        break;
                case 1:
                        diode = true;
                        break;
                default:
                        dev_warn(ds1307->dev,
                                 "unsupported aux-voltage-chargeable value\n");
                        break;
                }
        } else if (device_property_read_bool(ds1307->dev,
                                             "trickle-diode-disable")) {
                diode = false;
        }

        return chip->do_trickle_setup(ds1307, ohms, diode);
}

/*----------------------------------------------------------------------*/

#if IS_REACHABLE(CONFIG_HWMON)

/*
 * Temperature sensor support for ds3231 devices.
 */

#define DS3231_REG_TEMPERATURE  0x11

/*
 * A user-initiated temperature conversion is not started by this function,
 * so the temperature is updated once every 64 seconds.
 */
static int ds3231_hwmon_read_temp(struct device *dev, s32 *mC)
{
        struct ds1307 *ds1307 = dev_get_drvdata(dev);
        u8 temp_buf[2];
        s16 temp;
        int ret;

        ret = regmap_bulk_read(ds1307->regmap, DS3231_REG_TEMPERATURE,
                               temp_buf, sizeof(temp_buf));
        if (ret)
                return ret;
        /*
         * Temperature is represented as a 10-bit code with a resolution of
         * 0.25 degree celsius and encoded in two's complement format.
         */
        temp = (temp_buf[0] << 8) | temp_buf[1];
        temp >>= 6;
        *mC = temp * 250;

        return 0;
}

static ssize_t ds3231_hwmon_show_temp(struct device *dev,
                                      struct device_attribute *attr, char *buf)
{
        int ret;
        s32 temp;

        ret = ds3231_hwmon_read_temp(dev, &temp);
        if (ret)
                return ret;

        return sprintf(buf, "%d\n", temp);
}
static SENSOR_DEVICE_ATTR(temp1_input, 0444, ds3231_hwmon_show_temp,
                          NULL, 0);

static struct attribute *ds3231_hwmon_attrs[] = {
        &sensor_dev_attr_temp1_input.dev_attr.attr,
        NULL,
};
ATTRIBUTE_GROUPS(ds3231_hwmon);

static void ds1307_hwmon_register(struct ds1307 *ds1307)
{
        struct device *dev;

        if (ds1307->type != ds_3231)
                return;

        dev = devm_hwmon_device_register_with_groups(ds1307->dev, ds1307->name,
                                                     ds1307,
                                                     ds3231_hwmon_groups);
        if (IS_ERR(dev)) {
                dev_warn(ds1307->dev, "unable to register hwmon device %ld\n",
                         PTR_ERR(dev));
        }
}

#else

static void ds1307_hwmon_register(struct ds1307 *ds1307)
{
}

#endif /* CONFIG_RTC_DRV_DS1307_HWMON */

/*----------------------------------------------------------------------*/

/*
 * Square-wave output support for DS3231
 * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS3231.pdf
 */
#ifdef CONFIG_COMMON_CLK

enum {
        DS3231_CLK_SQW = 0,
        DS3231_CLK_32KHZ,
};

#define clk_sqw_to_ds1307(clk)  \
        container_of(clk, struct ds1307, clks[DS3231_CLK_SQW])
#define clk_32khz_to_ds1307(clk)        \
        container_of(clk, struct ds1307, clks[DS3231_CLK_32KHZ])

static int ds3231_clk_sqw_rates[] = {
        1,
        1024,
        4096,
        8192,
};

static int ds1337_write_control(struct ds1307 *ds1307, u8 mask, u8 value)
{
        struct mutex *lock = &ds1307->rtc->ops_lock;
        int ret;

        mutex_lock(lock);
        ret = regmap_update_bits(ds1307->regmap, DS1337_REG_CONTROL,
                                 mask, value);
        mutex_unlock(lock);

        return ret;
}

static unsigned long ds3231_clk_sqw_recalc_rate(struct clk_hw *hw,
                                                unsigned long parent_rate)
{
        struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
        int control, ret;
        int rate_sel = 0;

        ret = regmap_read(ds1307->regmap, DS1337_REG_CONTROL, &control);
        if (ret)
                return ret;
        if (control & DS1337_BIT_RS1)
                rate_sel += 1;
        if (control & DS1337_BIT_RS2)
                rate_sel += 2;

        return ds3231_clk_sqw_rates[rate_sel];
}

static int ds3231_clk_sqw_determine_rate(struct clk_hw *hw,
                                         struct clk_rate_request *req)
{
        int i;

        for (i = ARRAY_SIZE(ds3231_clk_sqw_rates) - 1; i >= 0; i--) {
                if (ds3231_clk_sqw_rates[i] <= req->rate) {
                        req->rate = ds3231_clk_sqw_rates[i];

                        return 0;
                }
        }

        req->rate = ds3231_clk_sqw_rates[ARRAY_SIZE(ds3231_clk_sqw_rates) - 1];

        return 0;
}

static int ds3231_clk_sqw_set_rate(struct clk_hw *hw, unsigned long rate,
                                   unsigned long parent_rate)
{
        struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
        int control = 0;
        int rate_sel;

        for (rate_sel = 0; rate_sel < ARRAY_SIZE(ds3231_clk_sqw_rates);
                        rate_sel++) {
                if (ds3231_clk_sqw_rates[rate_sel] == rate)
                        break;
        }

        if (rate_sel == ARRAY_SIZE(ds3231_clk_sqw_rates))
                return -EINVAL;

        if (rate_sel & 1)
                control |= DS1337_BIT_RS1;
        if (rate_sel & 2)
                control |= DS1337_BIT_RS2;

        return ds1337_write_control(ds1307, DS1337_BIT_RS1 | DS1337_BIT_RS2,
                                control);
}

static int ds3231_clk_sqw_prepare(struct clk_hw *hw)
{
        struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);

        return ds1337_write_control(ds1307, DS1337_BIT_INTCN, 0);
}

static void ds3231_clk_sqw_unprepare(struct clk_hw *hw)
{
        struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);

        ds1337_write_control(ds1307, DS1337_BIT_INTCN, DS1337_BIT_INTCN);
}

static int ds3231_clk_sqw_is_prepared(struct clk_hw *hw)
{
        struct ds1307 *ds1307 = clk_sqw_to_ds1307(hw);
        int control, ret;

        ret = regmap_read(ds1307->regmap, DS1337_REG_CONTROL, &control);
        if (ret)
                return ret;

        return !(control & DS1337_BIT_INTCN);
}

static const struct clk_ops ds3231_clk_sqw_ops = {
        .prepare = ds3231_clk_sqw_prepare,
        .unprepare = ds3231_clk_sqw_unprepare,
        .is_prepared = ds3231_clk_sqw_is_prepared,
        .recalc_rate = ds3231_clk_sqw_recalc_rate,
        .determine_rate = ds3231_clk_sqw_determine_rate,
        .set_rate = ds3231_clk_sqw_set_rate,
};

static unsigned long ds3231_clk_32khz_recalc_rate(struct clk_hw *hw,
                                                  unsigned long parent_rate)
{
        return 32768;
}

static int ds3231_clk_32khz_control(struct ds1307 *ds1307, bool enable)
{
        struct mutex *lock = &ds1307->rtc->ops_lock;
        int ret;

        mutex_lock(lock);
        ret = regmap_update_bits(ds1307->regmap, DS1337_REG_STATUS,
                                 DS3231_BIT_EN32KHZ,
                                 enable ? DS3231_BIT_EN32KHZ : 0);
        mutex_unlock(lock);

        return ret;
}

static int ds3231_clk_32khz_prepare(struct clk_hw *hw)
{
        struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);

        return ds3231_clk_32khz_control(ds1307, true);
}

static void ds3231_clk_32khz_unprepare(struct clk_hw *hw)
{
        struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);

        ds3231_clk_32khz_control(ds1307, false);
}

static int ds3231_clk_32khz_is_prepared(struct clk_hw *hw)
{
        struct ds1307 *ds1307 = clk_32khz_to_ds1307(hw);
        int status, ret;

        ret = regmap_read(ds1307->regmap, DS1337_REG_STATUS, &status);
        if (ret)
                return ret;

        return !!(status & DS3231_BIT_EN32KHZ);
}

static const struct clk_ops ds3231_clk_32khz_ops = {
        .prepare = ds3231_clk_32khz_prepare,
        .unprepare = ds3231_clk_32khz_unprepare,
        .is_prepared = ds3231_clk_32khz_is_prepared,
        .recalc_rate = ds3231_clk_32khz_recalc_rate,
};

static const char *ds3231_clks_names[] = {
        [DS3231_CLK_SQW] = "ds3231_clk_sqw",
        [DS3231_CLK_32KHZ] = "ds3231_clk_32khz",
};

static struct clk_init_data ds3231_clks_init[] = {
        [DS3231_CLK_SQW] = {
                .ops = &ds3231_clk_sqw_ops,
        },
        [DS3231_CLK_32KHZ] = {
                .ops = &ds3231_clk_32khz_ops,
        },
};

static int ds3231_clks_register(struct ds1307 *ds1307)
{
        struct device_node *node = ds1307->dev->of_node;
        struct clk_onecell_data *onecell;
        int i;

        onecell = devm_kzalloc(ds1307->dev, sizeof(*onecell), GFP_KERNEL);
        if (!onecell)
                return -ENOMEM;

        onecell->clk_num = ARRAY_SIZE(ds3231_clks_init);
        onecell->clks = devm_kcalloc(ds1307->dev, onecell->clk_num,
                                     sizeof(onecell->clks[0]), GFP_KERNEL);
        if (!onecell->clks)
                return -ENOMEM;

        /* optional override of the clockname */
        device_property_read_string_array(ds1307->dev, "clock-output-names",
                                          ds3231_clks_names,
                                          ARRAY_SIZE(ds3231_clks_names));

        for (i = 0; i < ARRAY_SIZE(ds3231_clks_init); i++) {
                struct clk_init_data init = ds3231_clks_init[i];

                /*
                 * Interrupt signal due to alarm conditions and square-wave
                 * output share same pin, so don't initialize both.
                 */
                if (i == DS3231_CLK_SQW && test_bit(RTC_FEATURE_ALARM, ds1307->rtc->features))
                        continue;

                init.name = ds3231_clks_names[i];
                ds1307->clks[i].init = &init;

                onecell->clks[i] = devm_clk_register(ds1307->dev,
                                                     &ds1307->clks[i]);
                if (IS_ERR(onecell->clks[i]))
                        return PTR_ERR(onecell->clks[i]);
        }

        if (node)
                of_clk_add_provider(node, of_clk_src_onecell_get, onecell);

        return 0;
}

static void ds1307_clks_register(struct ds1307 *ds1307)
{
        int ret;

        if (ds1307->type != ds_3231)
                return;

        ret = ds3231_clks_register(ds1307);
        if (ret) {
                dev_warn(ds1307->dev, "unable to register clock device %d\n",
                         ret);
        }
}

#else

static void ds1307_clks_register(struct ds1307 *ds1307)
{
}

#endif /* CONFIG_COMMON_CLK */

#ifdef CONFIG_WATCHDOG_CORE
static const struct watchdog_info ds1388_wdt_info = {
        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
        .identity = "DS1388 watchdog",
};

static const struct watchdog_ops ds1388_wdt_ops = {
        .owner = THIS_MODULE,
        .start = ds1388_wdt_start,
        .stop = ds1388_wdt_stop,
        .ping = ds1388_wdt_ping,
        .set_timeout = ds1388_wdt_set_timeout,

};

static void ds1307_wdt_register(struct ds1307 *ds1307)
{
        struct watchdog_device  *wdt;
        int err;
        int val;

        if (ds1307->type != ds_1388)
                return;

        wdt = devm_kzalloc(ds1307->dev, sizeof(*wdt), GFP_KERNEL);
        if (!wdt)
                return;

        err = regmap_read(ds1307->regmap, DS1388_REG_FLAG, &val);
        if (!err && val & DS1388_BIT_WF)
                wdt->bootstatus = WDIOF_CARDRESET;

        wdt->info = &ds1388_wdt_info;
        wdt->ops = &ds1388_wdt_ops;
        wdt->timeout = 99;
        wdt->max_timeout = 99;
        wdt->min_timeout = 1;

        watchdog_init_timeout(wdt, 0, ds1307->dev);
        watchdog_set_drvdata(wdt, ds1307);
        devm_watchdog_register_device(ds1307->dev, wdt);
}
#else
static void ds1307_wdt_register(struct ds1307 *ds1307)
{
}
#endif /* CONFIG_WATCHDOG_CORE */

static const struct regmap_config regmap_config = {
        .reg_bits = 8,
        .val_bits = 8,
};

static int ds1307_probe(struct i2c_client *client)
{
        const struct i2c_device_id *id = i2c_client_get_device_id(client);
        struct ds1307           *ds1307;
        const void              *match;
        int                     err = -ENODEV;
        int                     tmp;
        const struct chip_desc  *chip;
        bool                    want_irq;
        bool                    ds1307_can_wakeup_device = false;
        unsigned char           regs[8];
        struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev);
        u8                      trickle_charger_setup = 0;

        ds1307 = devm_kzalloc(&client->dev, sizeof(struct ds1307), GFP_KERNEL);
        if (!ds1307)
                return -ENOMEM;

        dev_set_drvdata(&client->dev, ds1307);
        ds1307->dev = &client->dev;
        ds1307->name = client->name;

        ds1307->regmap = devm_regmap_init_i2c(client, &regmap_config);
        if (IS_ERR(ds1307->regmap)) {
                dev_err(ds1307->dev, "regmap allocation failed\n");
                return PTR_ERR(ds1307->regmap);
        }

        i2c_set_clientdata(client, ds1307);

        match = device_get_match_data(&client->dev);
        if (match) {
                ds1307->type = (uintptr_t)match;
                chip = &chips[ds1307->type];
        } else if (id) {
                chip = &chips[id->driver_data];
                ds1307->type = id->driver_data;
        } else {
                return -ENODEV;
        }

        want_irq = client->irq > 0 && chip->alarm;

        if (!pdata)
                trickle_charger_setup = ds1307_trickle_init(ds1307, chip);
        else if (pdata->trickle_charger_setup)
                trickle_charger_setup = pdata->trickle_charger_setup;

        if (trickle_charger_setup && chip->trickle_charger_reg) {
                dev_dbg(ds1307->dev,
                        "writing trickle charger info 0x%x to 0x%x\n",
                        trickle_charger_setup, chip->trickle_charger_reg);
                regmap_write(ds1307->regmap, chip->trickle_charger_reg,
                             trickle_charger_setup);
        }

/*
 * For devices with no IRQ directly connected to the SoC, the RTC chip
 * can be forced as a wakeup source by stating that explicitly in
 * the device's .dts file using the "wakeup-source" boolean property.
 * If the "wakeup-source" property is set, don't request an IRQ.
 * This will guarantee the 'wakealarm' sysfs entry is available on the device,
 * if supported by the RTC.
 */
        if (chip->alarm && device_property_read_bool(&client->dev, "wakeup-source"))
                ds1307_can_wakeup_device = true;

        switch (ds1307->type) {
        case ds_1337:
        case ds_1339:
        case ds_1341:
        case ds_3231:
                /* get registers that the "rtc" read below won't read... */
                err = regmap_bulk_read(ds1307->regmap, DS1337_REG_CONTROL,
                                       regs, 2);
                if (err) {
                        dev_dbg(ds1307->dev, "read error %d\n", err);
                        goto exit;
                }

                /* oscillator off?  turn it on, so clock can tick. */
                if (regs[0] & DS1337_BIT_nEOSC)
                        regs[0] &= ~DS1337_BIT_nEOSC;

                /*
                 * Using IRQ or defined as wakeup-source?
                 * Disable the square wave and both alarms.
                 * For some variants, be sure alarms can trigger when we're
                 * running on Vbackup (BBSQI/BBSQW)
                 */
                if (want_irq || ds1307_can_wakeup_device)
                        regs[0] |= DS1337_BIT_INTCN | chip->bbsqi_bit;

                regmap_write(ds1307->regmap, DS1337_REG_CONTROL,
                             regs[0]);

                /* oscillator fault? warn */
                if (regs[1] & DS1337_BIT_OSF) {
                        dev_warn(ds1307->dev, "SET TIME!\n");
                }
                break;

        case rx_8025:
                err = regmap_bulk_read(ds1307->regmap,
                                       RX8025_REG_CTRL1 << 4 | 0x08, regs, 2);
                if (err) {
                        dev_dbg(ds1307->dev, "read error %d\n", err);
                        goto exit;
                }

                /* oscillator off?  turn it on, so clock can tick. */
                if (!(regs[1] & RX8025_BIT_XST)) {
                        regs[1] |= RX8025_BIT_XST;
                        regmap_write(ds1307->regmap,
                                     RX8025_REG_CTRL2 << 4 | 0x08,
                                     regs[1]);
                        dev_warn(ds1307->dev,
                                 "oscillator stop detected - SET TIME!\n");
                }

                if (regs[1] & RX8025_BIT_PON) {
                        regs[1] &= ~RX8025_BIT_PON;
                        regmap_write(ds1307->regmap,
                                     RX8025_REG_CTRL2 << 4 | 0x08,
                                     regs[1]);
                        dev_warn(ds1307->dev, "power-on detected\n");
                }

                if (regs[1] & RX8025_BIT_VDET) {
                        regs[1] &= ~RX8025_BIT_VDET;
                        regmap_write(ds1307->regmap,
                                     RX8025_REG_CTRL2 << 4 | 0x08,
                                     regs[1]);
                        dev_warn(ds1307->dev, "voltage drop detected\n");
                }

                /* make sure we are running in 24hour mode */
                if (!(regs[0] & RX8025_BIT_2412)) {
                        u8 hour;

                        /* switch to 24 hour mode */
                        regmap_write(ds1307->regmap,
                                     RX8025_REG_CTRL1 << 4 | 0x08,
                                     regs[0] | RX8025_BIT_2412);

                        err = regmap_bulk_read(ds1307->regmap,
                                               RX8025_REG_CTRL1 << 4 | 0x08,
                                               regs, 2);
                        if (err) {
                                dev_dbg(ds1307->dev, "read error %d\n", err);
                                goto exit;
                        }

                        /* correct hour */
                        hour = bcd2bin(regs[DS1307_REG_HOUR]);
                        if (hour == 12)
                                hour = 0;
                        if (regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
                                hour += 12;

                        regmap_write(ds1307->regmap,
                                     DS1307_REG_HOUR << 4 | 0x08, hour);
                }
                break;
        case ds_1388:
                err = regmap_read(ds1307->regmap, DS1388_REG_CONTROL, &tmp);
                if (err) {
                        dev_dbg(ds1307->dev, "read error %d\n", err);
                        goto exit;
                }

                /* oscillator off?  turn it on, so clock can tick. */
                if (tmp & DS1388_BIT_nEOSC) {
                        tmp &= ~DS1388_BIT_nEOSC;
                        regmap_write(ds1307->regmap, DS1388_REG_CONTROL, tmp);
                }
                break;
        default:
                break;
        }

        /* read RTC registers */
        err = regmap_bulk_read(ds1307->regmap, chip->offset, regs,
                               sizeof(regs));
        if (err) {
                dev_dbg(ds1307->dev, "read error %d\n", err);
                goto exit;
        }

        if (ds1307->type == mcp794xx &&
            !(regs[DS1307_REG_WDAY] & MCP794XX_BIT_VBATEN)) {
                regmap_write(ds1307->regmap, DS1307_REG_WDAY,
                             regs[DS1307_REG_WDAY] |
                             MCP794XX_BIT_VBATEN);
        }

        tmp = regs[DS1307_REG_HOUR];
        switch (ds1307->type) {
        case ds_1340:
        case m41t0:
        case m41t00:
        case m41t11:
                /*
                 * NOTE: ignores century bits; fix before deploying
                 * systems that will run through year 2100.
                 */
                break;
        case rx_8025:
                break;
        default:
                if (!(tmp & DS1307_BIT_12HR))
                        break;

                /*
                 * Be sure we're in 24 hour mode.  Multi-master systems
                 * take note...
                 */
                tmp = bcd2bin(tmp & 0x1f);
                if (tmp == 12)
                        tmp = 0;
                if (regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
                        tmp += 12;
                regmap_write(ds1307->regmap, chip->offset + DS1307_REG_HOUR,
                             bin2bcd(tmp));
        }

        ds1307->rtc = devm_rtc_allocate_device(ds1307->dev);
        if (IS_ERR(ds1307->rtc))
                return PTR_ERR(ds1307->rtc);

        if (want_irq || ds1307_can_wakeup_device)
                device_set_wakeup_capable(ds1307->dev, true);
        else
                clear_bit(RTC_FEATURE_ALARM, ds1307->rtc->features);

        if (ds1307_can_wakeup_device && !want_irq) {
                dev_info(ds1307->dev,
                         "'wakeup-source' is set, request for an IRQ is disabled!\n");
                /* We cannot support UIE mode if we do not have an IRQ line */
                clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, ds1307->rtc->features);
        }

        if (want_irq) {
                err = devm_request_threaded_irq(ds1307->dev, client->irq, NULL,
                                                chip->irq_handler ?: ds1307_irq,
                                                IRQF_SHARED | IRQF_ONESHOT,
                                                ds1307->name, ds1307);
                if (err) {
                        client->irq = 0;
                        device_set_wakeup_capable(ds1307->dev, false);
                        clear_bit(RTC_FEATURE_ALARM, ds1307->rtc->features);
                        dev_err(ds1307->dev, "unable to request IRQ!\n");
                } else {
                        dev_dbg(ds1307->dev, "got IRQ %d\n", client->irq);
                }
        }

        ds1307->rtc->ops = chip->rtc_ops ?: &ds13xx_rtc_ops;
        err = ds1307_add_frequency_test(ds1307);
        if (err)
                return err;

        err = devm_rtc_register_device(ds1307->rtc);
        if (err)
                return err;

        if (chip->nvram_size) {
                struct nvmem_config nvmem_cfg = {
                        .name = "ds1307_nvram",
                        .word_size = 1,
                        .stride = 1,
                        .size = chip->nvram_size,
                        .reg_read = ds1307_nvram_read,
                        .reg_write = ds1307_nvram_write,
                        .priv = ds1307,
                };

                devm_rtc_nvmem_register(ds1307->rtc, &nvmem_cfg);
        }

        ds1307_hwmon_register(ds1307);
        ds1307_clks_register(ds1307);
        ds1307_wdt_register(ds1307);

        return 0;

exit:
        return err;
}

static struct i2c_driver ds1307_driver = {
        .driver = {
                .name   = "rtc-ds1307",
                .of_match_table = ds1307_of_match,
        },
        .probe          = ds1307_probe,
        .id_table       = ds1307_id,
};

module_i2c_driver(ds1307_driver);

MODULE_DESCRIPTION("RTC driver for DS1307 and similar chips");
MODULE_LICENSE("GPL");