/*
 * 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)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/string.h>
#include <linux/rtc.h>
#include <linux/bcd.h>
#include <linux/rtc/ds1307.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 {
        ds_1307,
        ds_1337,
        ds_1338,
        ds_1339,
        ds_1340,
        ds_1388,
        ds_3231,
        m41t00,
        mcp794xx,
        rx_8025,
        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 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_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 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


struct ds1307 {
        u8                      offset; /* register's offset */
        u8                      regs[11];
        u16                     nvram_offset;
        struct bin_attribute    *nvram;
        enum ds_type            type;
        unsigned long           flags;
#define HAS_NVRAM       0               /* bit 0 == sysfs file active */
#define HAS_ALARM       1               /* bit 1 == irq claimed */
        struct i2c_client       *client;
        struct rtc_device       *rtc;
        struct work_struct      work;
        s32 (*read_block_data)(const struct i2c_client *client, u8 command,
                               u8 length, u8 *values);
        s32 (*write_block_data)(const struct i2c_client *client, u8 command,
                                u8 length, const u8 *values);
};

struct chip_desc {
        unsigned                alarm:1;
        u16                     nvram_offset;
        u16                     nvram_size;
        u16                     trickle_charger_reg;
        u8                      trickle_charger_setup;
        u8                      (*do_trickle_setup)(struct i2c_client *, uint32_t, bool);
};

static u8 do_trickle_setup_ds1339(struct i2c_client *,
                                  uint32_t ohms, bool diode);

static struct chip_desc chips[last_ds_type] = {
        [ds_1307] = {
                .nvram_offset   = 8,
                .nvram_size     = 56,
        },
        [ds_1337] = {
                .alarm          = 1,
        },
        [ds_1338] = {
                .nvram_offset   = 8,
                .nvram_size     = 56,
        },
        [ds_1339] = {
                .alarm          = 1,
                .trickle_charger_reg = 0x10,
                .do_trickle_setup = &do_trickle_setup_ds1339,
        },
        [ds_1340] = {
                .trickle_charger_reg = 0x08,
        },
        [ds_1388] = {
                .trickle_charger_reg = 0x0a,
        },
        [ds_3231] = {
                .alarm          = 1,
        },
        [mcp794xx] = {
                .alarm          = 1,
                /* this is battery backed SRAM */
                .nvram_offset   = 0x20,
                .nvram_size     = 0x40,
        },
};

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

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

#define BLOCK_DATA_MAX_TRIES 10

static s32 ds1307_read_block_data_once(const struct i2c_client *client,
                                       u8 command, u8 length, u8 *values)
{
        s32 i, data;

        for (i = 0; i < length; i++) {
                data = i2c_smbus_read_byte_data(client, command + i);
                if (data < 0)
                        return data;
                values[i] = data;
        }
        return i;
}

static s32 ds1307_read_block_data(const struct i2c_client *client, u8 command,
                                  u8 length, u8 *values)
{
        u8 oldvalues[255];
        s32 ret;
        int tries = 0;

        dev_dbg(&client->dev, "ds1307_read_block_data (length=%d)\n", length);
        ret = ds1307_read_block_data_once(client, command, length, values);
        if (ret < 0)
                return ret;
        do {
                if (++tries > BLOCK_DATA_MAX_TRIES) {
                        dev_err(&client->dev,
                                "ds1307_read_block_data failed\n");
                        return -EIO;
                }
                memcpy(oldvalues, values, length);
                ret = ds1307_read_block_data_once(client, command, length,
                                                  values);
                if (ret < 0)
                        return ret;
        } while (memcmp(oldvalues, values, length));
        return length;
}

static s32 ds1307_write_block_data(const struct i2c_client *client, u8 command,
                                   u8 length, const u8 *values)
{
        u8 currvalues[255];
        int tries = 0;

        dev_dbg(&client->dev, "ds1307_write_block_data (length=%d)\n", length);
        do {
                s32 i, ret;

                if (++tries > BLOCK_DATA_MAX_TRIES) {
                        dev_err(&client->dev,
                                "ds1307_write_block_data failed\n");
                        return -EIO;
                }
                for (i = 0; i < length; i++) {
                        ret = i2c_smbus_write_byte_data(client, command + i,
                                                        values[i]);
                        if (ret < 0)
                                return ret;
                }
                ret = ds1307_read_block_data_once(client, command, length,
                                                  currvalues);
                if (ret < 0)
                        return ret;
        } while (memcmp(currvalues, values, length));
        return length;
}

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

/* These RTC devices are not designed to be connected to a SMbus adapter.
   SMbus limits block operations length to 32 bytes, whereas it's not
   limited on I2C buses. As a result, accesses may exceed 32 bytes;
   in that case, split them into smaller blocks */

static s32 ds1307_native_smbus_write_block_data(const struct i2c_client *client,
                                u8 command, u8 length, const u8 *values)
{
        u8 suboffset = 0;

        if (length <= I2C_SMBUS_BLOCK_MAX)
                return i2c_smbus_write_i2c_block_data(client,
                                        command, length, values);

        while (suboffset < length) {
                s32 retval = i2c_smbus_write_i2c_block_data(client,
                                command + suboffset,
                                min(I2C_SMBUS_BLOCK_MAX, length - suboffset),
                                values + suboffset);
                if (retval < 0)
                        return retval;

                suboffset += I2C_SMBUS_BLOCK_MAX;
        }
        return length;
}

static s32 ds1307_native_smbus_read_block_data(const struct i2c_client *client,
                                u8 command, u8 length, u8 *values)
{
        u8 suboffset = 0;

        if (length <= I2C_SMBUS_BLOCK_MAX)
                return i2c_smbus_read_i2c_block_data(client,
                                        command, length, values);

        while (suboffset < length) {
                s32 retval = i2c_smbus_read_i2c_block_data(client,
                                command + suboffset,
                                min(I2C_SMBUS_BLOCK_MAX, length - suboffset),
                                values + suboffset);
                if (retval < 0)
                        return retval;

                suboffset += I2C_SMBUS_BLOCK_MAX;
        }
        return length;
}

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

/*
 * The IRQ logic includes a "real" handler running in IRQ context just
 * long enough to schedule this workqueue entry.   We need a task context
 * to talk to the RTC, since I2C I/O calls require that; and disable the
 * IRQ until we clear its status on the chip, so that this handler can
 * work with any type of triggering (not just falling edge).
 *
 * 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 void ds1307_work(struct work_struct *work)
{
        struct ds1307           *ds1307;
        struct i2c_client       *client;
        struct mutex            *lock;
        int                     stat, control;

        ds1307 = container_of(work, struct ds1307, work);
        client = ds1307->client;
        lock = &ds1307->rtc->ops_lock;

        mutex_lock(lock);
        stat = i2c_smbus_read_byte_data(client, DS1337_REG_STATUS);
        if (stat < 0)
                goto out;

        if (stat & DS1337_BIT_A1I) {
                stat &= ~DS1337_BIT_A1I;
                i2c_smbus_write_byte_data(client, DS1337_REG_STATUS, stat);

                control = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
                if (control < 0)
                        goto out;

                control &= ~DS1337_BIT_A1IE;
                i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, control);

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

out:
        if (test_bit(HAS_ALARM, &ds1307->flags))
                enable_irq(client->irq);
        mutex_unlock(lock);
}

static irqreturn_t ds1307_irq(int irq, void *dev_id)
{
        struct i2c_client       *client = dev_id;
        struct ds1307           *ds1307 = i2c_get_clientdata(client);

        disable_irq_nosync(irq);
        schedule_work(&ds1307->work);
        return IRQ_HANDLED;
}

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

static int ds1307_get_time(struct device *dev, struct rtc_time *t)
{
        struct ds1307   *ds1307 = dev_get_drvdata(dev);
        int             tmp;

        /* read the RTC date and time registers all at once */
        tmp = ds1307->read_block_data(ds1307->client,
                ds1307->offset, 7, ds1307->regs);
        if (tmp != 7) {
                dev_err(dev, "%s error %d\n", "read", tmp);
                return -EIO;
        }

        dev_dbg(dev, "%s: %7ph\n", "read", ds1307->regs);

        t->tm_sec = bcd2bin(ds1307->regs[DS1307_REG_SECS] & 0x7f);
        t->tm_min = bcd2bin(ds1307->regs[DS1307_REG_MIN] & 0x7f);
        tmp = ds1307->regs[DS1307_REG_HOUR] & 0x3f;
        t->tm_hour = bcd2bin(tmp);
        t->tm_wday = bcd2bin(ds1307->regs[DS1307_REG_WDAY] & 0x07) - 1;
        t->tm_mday = bcd2bin(ds1307->regs[DS1307_REG_MDAY] & 0x3f);
        tmp = ds1307->regs[DS1307_REG_MONTH] & 0x1f;
        t->tm_mon = bcd2bin(tmp) - 1;

        /* assume 20YY not 19YY, and ignore DS1337_BIT_CENTURY */
        t->tm_year = bcd2bin(ds1307->regs[DS1307_REG_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);

        /* initial clock setting can be undefined */
        return rtc_valid_tm(t);
}

static int ds1307_set_time(struct device *dev, struct rtc_time *t)
{
        struct ds1307   *ds1307 = dev_get_drvdata(dev);
        int             result;
        int             tmp;
        u8              *buf = ds1307->regs;

        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);

        buf[DS1307_REG_SECS] = bin2bcd(t->tm_sec);
        buf[DS1307_REG_MIN] = bin2bcd(t->tm_min);
        buf[DS1307_REG_HOUR] = bin2bcd(t->tm_hour);
        buf[DS1307_REG_WDAY] = bin2bcd(t->tm_wday + 1);
        buf[DS1307_REG_MDAY] = bin2bcd(t->tm_mday);
        buf[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);

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

        switch (ds1307->type) {
        case ds_1337:
        case ds_1339:
        case ds_3231:
                buf[DS1307_REG_MONTH] |= DS1337_BIT_CENTURY;
                break;
        case ds_1340:
                buf[DS1307_REG_HOUR] |= DS1340_BIT_CENTURY_EN
                                | DS1340_BIT_CENTURY;
                break;
        case mcp794xx:
                /*
                 * these bits were cleared when preparing the date/time
                 * values and need to be set again before writing the
                 * buffer out to the device.
                 */
                buf[DS1307_REG_SECS] |= MCP794XX_BIT_ST;
                buf[DS1307_REG_WDAY] |= MCP794XX_BIT_VBATEN;
                break;
        default:
                break;
        }

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

        result = ds1307->write_block_data(ds1307->client,
                ds1307->offset, 7, buf);
        if (result < 0) {
                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 i2c_client       *client = to_i2c_client(dev);
        struct ds1307           *ds1307 = i2c_get_clientdata(client);
        int                     ret;

        if (!test_bit(HAS_ALARM, &ds1307->flags))
                return -EINVAL;

        /* read all ALARM1, ALARM2, and status registers at once */
        ret = ds1307->read_block_data(client,
                        DS1339_REG_ALARM1_SECS, 9, ds1307->regs);
        if (ret != 9) {
                dev_err(dev, "%s error %d\n", "alarm read", ret);
                return -EIO;
        }

        dev_dbg(dev, "%s: %02x %02x %02x %02x, %02x %02x %02x, %02x %02x\n",
                        "alarm read",
                        ds1307->regs[0], ds1307->regs[1],
                        ds1307->regs[2], ds1307->regs[3],
                        ds1307->regs[4], ds1307->regs[5],
                        ds1307->regs[6], ds1307->regs[7],
                        ds1307->regs[8]);

        /*
         * 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(ds1307->regs[0] & 0x7f);
        t->time.tm_min = bcd2bin(ds1307->regs[1] & 0x7f);
        t->time.tm_hour = bcd2bin(ds1307->regs[2] & 0x3f);
        t->time.tm_mday = bcd2bin(ds1307->regs[3] & 0x3f);
        t->time.tm_mon = -1;
        t->time.tm_year = -1;
        t->time.tm_wday = -1;
        t->time.tm_yday = -1;
        t->time.tm_isdst = -1;

        /* ... and status */
        t->enabled = !!(ds1307->regs[7] & DS1337_BIT_A1IE);
        t->pending = !!(ds1307->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 i2c_client       *client = to_i2c_client(dev);
        struct ds1307           *ds1307 = i2c_get_clientdata(client);
        unsigned char           *buf = ds1307->regs;
        u8                      control, status;
        int                     ret;

        if (!test_bit(HAS_ALARM, &ds1307->flags))
                return -EINVAL;

        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 = ds1307->read_block_data(client,
                        DS1339_REG_ALARM1_SECS, 9, buf);
        if (ret != 9) {
                dev_err(dev, "%s error %d\n", "alarm write", ret);
                return -EIO;
        }
        control = ds1307->regs[7];
        status = ds1307->regs[8];

        dev_dbg(dev, "%s: %02x %02x %02x %02x, %02x %02x %02x, %02x %02x\n",
                        "alarm set (old status)",
                        ds1307->regs[0], ds1307->regs[1],
                        ds1307->regs[2], ds1307->regs[3],
                        ds1307->regs[4], ds1307->regs[5],
                        ds1307->regs[6], control, status);

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

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

        /* optionally enable ALARM1 */
        buf[7] = control & ~(DS1337_BIT_A1IE | DS1337_BIT_A2IE);
        if (t->enabled) {
                dev_dbg(dev, "alarm IRQ armed\n");
                buf[7] |= DS1337_BIT_A1IE;      /* only ALARM1 is used */
        }
        buf[8] = status & ~(DS1337_BIT_A1I | DS1337_BIT_A2I);

        ret = ds1307->write_block_data(client,
                        DS1339_REG_ALARM1_SECS, 9, buf);
        if (ret < 0) {
                dev_err(dev, "can't set alarm time\n");
                return ret;
        }

        return 0;
}

static int ds1307_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct i2c_client       *client = to_i2c_client(dev);
        struct ds1307           *ds1307 = i2c_get_clientdata(client);
        int                     ret;

        if (!test_bit(HAS_ALARM, &ds1307->flags))
                return -ENOTTY;

        ret = i2c_smbus_read_byte_data(client, DS1337_REG_CONTROL);
        if (ret < 0)
                return ret;

        if (enabled)
                ret |= DS1337_BIT_A1IE;
        else
                ret &= ~DS1337_BIT_A1IE;

        ret = i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL, ret);
        if (ret < 0)
                return ret;

        return 0;
}

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,
};

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

/*
 * Alarm support for mcp794xx devices.
 */

#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     (1 << 3)
#       define MCP794XX_BIT_ALMX_C0     (1 << 4)
#       define MCP794XX_BIT_ALMX_C1     (1 << 5)
#       define MCP794XX_BIT_ALMX_C2     (1 << 6)
#       define MCP794XX_BIT_ALMX_POL    (1 << 7)
#       define MCP794XX_MSK_ALMX_MATCH  (MCP794XX_BIT_ALMX_C0 | \
                                         MCP794XX_BIT_ALMX_C1 | \
                                         MCP794XX_BIT_ALMX_C2)

static void mcp794xx_work(struct work_struct *work)
{
        struct ds1307 *ds1307 = container_of(work, struct ds1307, work);
        struct i2c_client *client = ds1307->client;
        int reg, ret;

        mutex_lock(&ds1307->rtc->ops_lock);

        /* Check and clear alarm 0 interrupt flag. */
        reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_ALARM0_CTRL);
        if (reg < 0)
                goto out;
        if (!(reg & MCP794XX_BIT_ALMX_IF))
                goto out;
        reg &= ~MCP794XX_BIT_ALMX_IF;
        ret = i2c_smbus_write_byte_data(client, MCP794XX_REG_ALARM0_CTRL, reg);
        if (ret < 0)
                goto out;

        /* Disable alarm 0. */
        reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_CONTROL);
        if (reg < 0)
                goto out;
        reg &= ~MCP794XX_BIT_ALM0_EN;
        ret = i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, reg);
        if (ret < 0)
                goto out;

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

out:
        if (test_bit(HAS_ALARM, &ds1307->flags))
                enable_irq(client->irq);
        mutex_unlock(&ds1307->rtc->ops_lock);
}

static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct ds1307 *ds1307 = i2c_get_clientdata(client);
        u8 *regs = ds1307->regs;
        int ret;

        if (!test_bit(HAS_ALARM, &ds1307->flags))
                return -EINVAL;

        /* Read control and alarm 0 registers. */
        ret = ds1307->read_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
        if (ret < 0)
                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(ds1307->regs[3] & 0x7f);
        t->time.tm_min = bcd2bin(ds1307->regs[4] & 0x7f);
        t->time.tm_hour = bcd2bin(ds1307->regs[5] & 0x3f);
        t->time.tm_wday = bcd2bin(ds1307->regs[6] & 0x7) - 1;
        t->time.tm_mday = bcd2bin(ds1307->regs[7] & 0x3f);
        t->time.tm_mon = bcd2bin(ds1307->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=%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,
                !!(ds1307->regs[6] & MCP794XX_BIT_ALMX_POL),
                !!(ds1307->regs[6] & MCP794XX_BIT_ALMX_IF),
                (ds1307->regs[6] & MCP794XX_MSK_ALMX_MATCH) >> 4);

        return 0;
}

static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct ds1307 *ds1307 = i2c_get_clientdata(client);
        unsigned char *regs = ds1307->regs;
        int ret;

        if (!test_bit(HAS_ALARM, &ds1307->flags))
                return -EINVAL;

        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 = ds1307->read_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
        if (ret < 0)
                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] = bin2bcd(t->time.tm_wday) + 1;
        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;

        if (t->enabled)
                regs[0] |= MCP794XX_BIT_ALM0_EN;
        else
                regs[0] &= ~MCP794XX_BIT_ALM0_EN;

        ret = ds1307->write_block_data(client, MCP794XX_REG_CONTROL, 10, regs);
        if (ret < 0)
                return ret;

        return 0;
}

static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct ds1307 *ds1307 = i2c_get_clientdata(client);
        int reg;

        if (!test_bit(HAS_ALARM, &ds1307->flags))
                return -EINVAL;

        reg = i2c_smbus_read_byte_data(client, MCP794XX_REG_CONTROL);
        if (reg < 0)
                return reg;

        if (enabled)
                reg |= MCP794XX_BIT_ALM0_EN;
        else
                reg &= ~MCP794XX_BIT_ALM0_EN;

        return i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, reg);
}

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 ssize_t
ds1307_nvram_read(struct file *filp, struct kobject *kobj,
                struct bin_attribute *attr,
                char *buf, loff_t off, size_t count)
{
        struct i2c_client       *client;
        struct ds1307           *ds1307;
        int                     result;

        client = kobj_to_i2c_client(kobj);
        ds1307 = i2c_get_clientdata(client);

        if (unlikely(off >= ds1307->nvram->size))
                return 0;
        if ((off + count) > ds1307->nvram->size)
                count = ds1307->nvram->size - off;
        if (unlikely(!count))
                return count;

        result = ds1307->read_block_data(client, ds1307->nvram_offset + off,
                                                                count, buf);
        if (result < 0)
                dev_err(&client->dev, "%s error %d\n", "nvram read", result);
        return result;
}

static ssize_t
ds1307_nvram_write(struct file *filp, struct kobject *kobj,
                struct bin_attribute *attr,
                char *buf, loff_t off, size_t count)
{
        struct i2c_client       *client;
        struct ds1307           *ds1307;
        int                     result;

        client = kobj_to_i2c_client(kobj);
        ds1307 = i2c_get_clientdata(client);

        if (unlikely(off >= ds1307->nvram->size))
                return -EFBIG;
        if ((off + count) > ds1307->nvram->size)
                count = ds1307->nvram->size - off;
        if (unlikely(!count))
                return count;

        result = ds1307->write_block_data(client, ds1307->nvram_offset + off,
                                                                count, buf);
        if (result < 0) {
                dev_err(&client->dev, "%s error %d\n", "nvram write", result);
                return result;
        }
        return count;
}


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

static u8 do_trickle_setup_ds1339(struct i2c_client *client,
                                  uint32_t ohms, bool diode)
{
        u8 setup = (diode) ? DS1307_TRICKLE_CHARGER_DIODE :
                DS1307_TRICKLE_CHARGER_NO_DIODE;

        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(&client->dev,
                         "Unsupported ohm value %u in dt\n", ohms);
                return 0;
        }
        return setup;
}

static void ds1307_trickle_of_init(struct i2c_client *client,
                                   struct chip_desc *chip)
{
        uint32_t ohms = 0;
        bool diode = true;

        if (!chip->do_trickle_setup)
                goto out;
        if (of_property_read_u32(client->dev.of_node, "trickle-resistor-ohms" , &ohms))
                goto out;
        if (of_property_read_bool(client->dev.of_node, "trickle-diode-disable"))
                diode = false;
        chip->trickle_charger_setup = chip->do_trickle_setup(client,
                                                             ohms, diode);
out:
        return;
}

static int ds1307_probe(struct i2c_client *client,
                        const struct i2c_device_id *id)
{
        struct ds1307           *ds1307;
        int                     err = -ENODEV;
        int                     tmp;
        struct chip_desc        *chip = &chips[id->driver_data];
        struct i2c_adapter      *adapter = to_i2c_adapter(client->dev.parent);
        bool                    want_irq = false;
        unsigned char           *buf;
        struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev);
        static const int        bbsqi_bitpos[] = {
                [ds_1337] = 0,
                [ds_1339] = DS1339_BIT_BBSQI,
                [ds_3231] = DS3231_BIT_BBSQW,
        };
        const struct rtc_class_ops *rtc_ops = &ds13xx_rtc_ops;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)
            && !i2c_check_functionality(adapter, I2C_FUNC_SMBUS_I2C_BLOCK))
                return -EIO;

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

        i2c_set_clientdata(client, ds1307);

        ds1307->client  = client;
        ds1307->type    = id->driver_data;

        if (!pdata && client->dev.of_node)
                ds1307_trickle_of_init(client, chip);
        else if (pdata && pdata->trickle_charger_setup)
                chip->trickle_charger_setup = pdata->trickle_charger_setup;

        if (chip->trickle_charger_setup && chip->trickle_charger_reg) {
                dev_dbg(&client->dev, "writing trickle charger info 0x%x to 0x%x\n",
                    DS13XX_TRICKLE_CHARGER_MAGIC | chip->trickle_charger_setup,
                    chip->trickle_charger_reg);
                i2c_smbus_write_byte_data(client, chip->trickle_charger_reg,
                    DS13XX_TRICKLE_CHARGER_MAGIC |
                    chip->trickle_charger_setup);
        }

        buf = ds1307->regs;
        if (i2c_check_functionality(adapter, I2C_FUNC_SMBUS_I2C_BLOCK)) {
                ds1307->read_block_data = ds1307_native_smbus_read_block_data;
                ds1307->write_block_data = ds1307_native_smbus_write_block_data;
        } else {
                ds1307->read_block_data = ds1307_read_block_data;
                ds1307->write_block_data = ds1307_write_block_data;
        }

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

                /* oscillator off?  turn it on, so clock can tick. */
                if (ds1307->regs[0] & DS1337_BIT_nEOSC)
                        ds1307->regs[0] &= ~DS1337_BIT_nEOSC;

                /*
                 * Using IRQ?  Disable the square wave and both alarms.
                 * For some variants, be sure alarms can trigger when we're
                 * running on Vbackup (BBSQI/BBSQW)
                 */
                if (ds1307->client->irq > 0 && chip->alarm) {
                        INIT_WORK(&ds1307->work, ds1307_work);

                        ds1307->regs[0] |= DS1337_BIT_INTCN
                                        | bbsqi_bitpos[ds1307->type];
                        ds1307->regs[0] &= ~(DS1337_BIT_A2IE | DS1337_BIT_A1IE);

                        want_irq = true;
                }

                i2c_smbus_write_byte_data(client, DS1337_REG_CONTROL,
                                                        ds1307->regs[0]);

                /* oscillator fault?  clear flag, and warn */
                if (ds1307->regs[1] & DS1337_BIT_OSF) {
                        i2c_smbus_write_byte_data(client, DS1337_REG_STATUS,
                                ds1307->regs[1] & ~DS1337_BIT_OSF);
                        dev_warn(&client->dev, "SET TIME!\n");
                }
                break;

        case rx_8025:
                tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
                                RX8025_REG_CTRL1 << 4 | 0x08, 2, buf);
                if (tmp != 2) {
                        dev_dbg(&client->dev, "read error %d\n", tmp);
                        err = -EIO;
                        goto exit;
                }

                /* oscillator off?  turn it on, so clock can tick. */
                if (!(ds1307->regs[1] & RX8025_BIT_XST)) {
                        ds1307->regs[1] |= RX8025_BIT_XST;
                        i2c_smbus_write_byte_data(client,
                                                  RX8025_REG_CTRL2 << 4 | 0x08,
                                                  ds1307->regs[1]);
                        dev_warn(&client->dev,

                                 "oscillator stop detected - SET TIME!\n");
                }

                if (ds1307->regs[1] & RX8025_BIT_PON) {
                        ds1307->regs[1] &= ~RX8025_BIT_PON;
                        i2c_smbus_write_byte_data(client,
                                                  RX8025_REG_CTRL2 << 4 | 0x08,
                                                  ds1307->regs[1]);
                        dev_warn(&client->dev, "power-on detected\n");
                }

                if (ds1307->regs[1] & RX8025_BIT_VDET) {
                        ds1307->regs[1] &= ~RX8025_BIT_VDET;
                        i2c_smbus_write_byte_data(client,
                                                  RX8025_REG_CTRL2 << 4 | 0x08,
                                                  ds1307->regs[1]);
                        dev_warn(&client->dev, "voltage drop detected\n");
                }

                /* make sure we are running in 24hour mode */
                if (!(ds1307->regs[0] & RX8025_BIT_2412)) {
                        u8 hour;

                        /* switch to 24 hour mode */
                        i2c_smbus_write_byte_data(client,
                                                  RX8025_REG_CTRL1 << 4 | 0x08,
                                                  ds1307->regs[0] |
                                                  RX8025_BIT_2412);

                        tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
                                        RX8025_REG_CTRL1 << 4 | 0x08, 2, buf);
                        if (tmp != 2) {
                                dev_dbg(&client->dev, "read error %d\n", tmp);
                                err = -EIO;
                                goto exit;
                        }

                        /* correct hour */
                        hour = bcd2bin(ds1307->regs[DS1307_REG_HOUR]);
                        if (hour == 12)
                                hour = 0;
                        if (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
                                hour += 12;

                        i2c_smbus_write_byte_data(client,
                                                  DS1307_REG_HOUR << 4 | 0x08,
                                                  hour);
                }
                break;
        case ds_1388:
                ds1307->offset = 1; /* Seconds starts at 1 */
                break;
        case mcp794xx:
                rtc_ops = &mcp794xx_rtc_ops;
                if (ds1307->client->irq > 0 && chip->alarm) {
                        INIT_WORK(&ds1307->work, mcp794xx_work);
                        want_irq = true;
                }
                break;
        default:
                break;
        }

read_rtc:
        /* read RTC registers */
        tmp = ds1307->read_block_data(ds1307->client, ds1307->offset, 8, buf);
        if (tmp != 8) {
                dev_dbg(&client->dev, "read error %d\n", tmp);
                err = -EIO;
                goto exit;
        }

        /*
         * minimal sanity checking; some chips (like DS1340) don't
         * specify the extra bits as must-be-zero, but there are
         * still a few values that are clearly out-of-range.
         */
        tmp = ds1307->regs[DS1307_REG_SECS];
        switch (ds1307->type) {
        case ds_1307:
        case m41t00:
                /* clock halted?  turn it on, so clock can tick. */
                if (tmp & DS1307_BIT_CH) {
                        i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);
                        dev_warn(&client->dev, "SET TIME!\n");
                        goto read_rtc;
                }
                break;
        case ds_1338:
                /* clock halted?  turn it on, so clock can tick. */
                if (tmp & DS1307_BIT_CH)
                        i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);

                /* oscillator fault?  clear flag, and warn */
                if (ds1307->regs[DS1307_REG_CONTROL] & DS1338_BIT_OSF) {
                        i2c_smbus_write_byte_data(client, DS1307_REG_CONTROL,
                                        ds1307->regs[DS1307_REG_CONTROL]
                                        & ~DS1338_BIT_OSF);
                        dev_warn(&client->dev, "SET TIME!\n");
                        goto read_rtc;
                }
                break;
        case ds_1340:
                /* clock halted?  turn it on, so clock can tick. */
                if (tmp & DS1340_BIT_nEOSC)
                        i2c_smbus_write_byte_data(client, DS1307_REG_SECS, 0);

                tmp = i2c_smbus_read_byte_data(client, DS1340_REG_FLAG);
                if (tmp < 0) {
                        dev_dbg(&client->dev, "read error %d\n", tmp);
                        err = -EIO;
                        goto exit;
                }

                /* oscillator fault?  clear flag, and warn */
                if (tmp & DS1340_BIT_OSF) {
                        i2c_smbus_write_byte_data(client, DS1340_REG_FLAG, 0);
                        dev_warn(&client->dev, "SET TIME!\n");
                }
                break;
        case mcp794xx:
                /* make sure that the backup battery is enabled */
                if (!(ds1307->regs[DS1307_REG_WDAY] & MCP794XX_BIT_VBATEN)) {
                        i2c_smbus_write_byte_data(client, DS1307_REG_WDAY,
                                        ds1307->regs[DS1307_REG_WDAY]
                                        | MCP794XX_BIT_VBATEN);
                }

                /* clock halted?  turn it on, so clock can tick. */
                if (!(tmp & MCP794XX_BIT_ST)) {
                        i2c_smbus_write_byte_data(client, DS1307_REG_SECS,
                                        MCP794XX_BIT_ST);
                        dev_warn(&client->dev, "SET TIME!\n");
                        goto read_rtc;
                }

                break;
        default:
                break;
        }

        tmp = ds1307->regs[DS1307_REG_HOUR];
        switch (ds1307->type) {
        case ds_1340:
        case m41t00:
                /*
                 * 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 (ds1307->regs[DS1307_REG_HOUR] & DS1307_BIT_PM)
                        tmp += 12;
                i2c_smbus_write_byte_data(client,
                                ds1307->offset + DS1307_REG_HOUR,
                                bin2bcd(tmp));
        }

        device_set_wakeup_capable(&client->dev, want_irq);
        ds1307->rtc = devm_rtc_device_register(&client->dev, client->name,
                                rtc_ops, THIS_MODULE);
        if (IS_ERR(ds1307->rtc)) {
                return PTR_ERR(ds1307->rtc);
        }

        if (want_irq) {
                err = request_irq(client->irq, ds1307_irq, IRQF_SHARED,
                          ds1307->rtc->name, client);
                if (err) {
                        client->irq = 0;
                        dev_err(&client->dev, "unable to request IRQ!\n");
                } else {

                        set_bit(HAS_ALARM, &ds1307->flags);
                        dev_dbg(&client->dev, "got IRQ %d\n", client->irq);
                }
        }

        if (chip->nvram_size) {

                ds1307->nvram = devm_kzalloc(&client->dev,
                                        sizeof(struct bin_attribute),
                                        GFP_KERNEL);
                if (!ds1307->nvram) {
                        dev_err(&client->dev, "cannot allocate memory for nvram sysfs\n");
                } else {

                        ds1307->nvram->attr.name = "nvram";
                        ds1307->nvram->attr.mode = S_IRUGO | S_IWUSR;

                        sysfs_bin_attr_init(ds1307->nvram);

                        ds1307->nvram->read = ds1307_nvram_read;
                        ds1307->nvram->write = ds1307_nvram_write;
                        ds1307->nvram->size = chip->nvram_size;
                        ds1307->nvram_offset = chip->nvram_offset;

                        err = sysfs_create_bin_file(&client->dev.kobj,
                                                    ds1307->nvram);
                        if (err) {
                                dev_err(&client->dev,
                                        "unable to create sysfs file: %s\n",
                                        ds1307->nvram->attr.name);
                        } else {
                                set_bit(HAS_NVRAM, &ds1307->flags);
                                dev_info(&client->dev, "%zu bytes nvram\n",
                                         ds1307->nvram->size);
                        }
                }
        }

        return 0;

exit:
        return err;
}

static int ds1307_remove(struct i2c_client *client)
{
        struct ds1307 *ds1307 = i2c_get_clientdata(client);

        if (test_and_clear_bit(HAS_ALARM, &ds1307->flags)) {
                free_irq(client->irq, client);
                cancel_work_sync(&ds1307->work);
        }

        if (test_and_clear_bit(HAS_NVRAM, &ds1307->flags))
                sysfs_remove_bin_file(&client->dev.kobj, ds1307->nvram);

        return 0;
}

static struct i2c_driver ds1307_driver = {
        .driver = {
                .name   = "rtc-ds1307",
                .owner  = THIS_MODULE,
        },
        .probe          = ds1307_probe,
        .remove         = ds1307_remove,
        .id_table       = ds1307_id,
};

module_i2c_driver(ds1307_driver);

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