// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Intersil ISL1208 rtc class driver
 *
 * Copyright 2005,2006 Hebert Valerio Riedel <hvr@gnu.org>
 */

#include <linux/bcd.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/rtc.h>

/* Register map */
/* rtc section */
#define ISL1208_REG_SC  0x00
#define ISL1208_REG_MN  0x01
#define ISL1208_REG_HR  0x02
#define ISL1208_REG_HR_MIL     (1<<7)   /* 24h/12h mode */
#define ISL1208_REG_HR_PM      (1<<5)   /* PM/AM bit in 12h mode */
#define ISL1208_REG_DT  0x03
#define ISL1208_REG_MO  0x04
#define ISL1208_REG_YR  0x05
#define ISL1208_REG_DW  0x06
#define ISL1208_RTC_SECTION_LEN 7

/* control/status section */
#define ISL1208_REG_SR  0x07
#define ISL1208_REG_SR_ARST    (1<<7)   /* auto reset */
#define ISL1208_REG_SR_XTOSCB  (1<<6)   /* crystal oscillator */
#define ISL1208_REG_SR_WRTC    (1<<4)   /* write rtc */
#define ISL1208_REG_SR_EVT     (1<<3)   /* event */
#define ISL1208_REG_SR_ALM     (1<<2)   /* alarm */
#define ISL1208_REG_SR_BAT     (1<<1)   /* battery */
#define ISL1208_REG_SR_RTCF    (1<<0)   /* rtc fail */
#define ISL1208_REG_INT 0x08
#define ISL1208_REG_INT_ALME   (1<<6)   /* alarm enable */
#define ISL1208_REG_INT_IM     (1<<7)   /* interrupt/alarm mode */
#define ISL1219_REG_EV  0x09
#define ISL1219_REG_EV_EVEN    (1<<4)   /* event detection enable */
#define ISL1219_REG_EV_EVIENB  (1<<7)   /* event in pull-up disable */
#define ISL1208_REG_ATR 0x0a
#define ISL1208_REG_DTR 0x0b

/* alarm section */
#define ISL1208_REG_SCA 0x0c
#define ISL1208_REG_MNA 0x0d
#define ISL1208_REG_HRA 0x0e
#define ISL1208_REG_DTA 0x0f
#define ISL1208_REG_MOA 0x10
#define ISL1208_REG_DWA 0x11
#define ISL1208_ALARM_SECTION_LEN 6

/* user section */
#define ISL1208_REG_USR1 0x12
#define ISL1208_REG_USR2 0x13
#define ISL1208_USR_SECTION_LEN 2

/* event section */
#define ISL1219_REG_SCT 0x14
#define ISL1219_REG_MNT 0x15
#define ISL1219_REG_HRT 0x16
#define ISL1219_REG_DTT 0x17
#define ISL1219_REG_MOT 0x18
#define ISL1219_REG_YRT 0x19
#define ISL1219_EVT_SECTION_LEN 6

static struct i2c_driver isl1208_driver;

/* Chip capabilities table */
struct isl1208_config {
        unsigned int    nvmem_length;
        unsigned        has_tamper:1;
        unsigned        has_timestamp:1;
        unsigned        has_inverted_osc_bit:1;
};

static const struct isl1208_config config_isl1208 = {
        .nvmem_length = 2,
        .has_tamper = false,
        .has_timestamp = false
};

static const struct isl1208_config config_isl1209 = {
        .nvmem_length = 2,
        .has_tamper = true,
        .has_timestamp = false
};

static const struct isl1208_config config_isl1218 = {
        .nvmem_length = 8,
        .has_tamper = false,
        .has_timestamp = false
};

static const struct isl1208_config config_isl1219 = {
        .nvmem_length = 2,
        .has_tamper = true,
        .has_timestamp = true
};

static const struct isl1208_config config_raa215300_a0 = {
        .nvmem_length = 2,
        .has_tamper = false,
        .has_timestamp = false,
        .has_inverted_osc_bit = true
};

static const struct i2c_device_id isl1208_id[] = {
        { "isl1208", .driver_data = (kernel_ulong_t)&config_isl1208 },
        { "isl1209", .driver_data = (kernel_ulong_t)&config_isl1209 },
        { "isl1218", .driver_data = (kernel_ulong_t)&config_isl1218 },
        { "isl1219", .driver_data = (kernel_ulong_t)&config_isl1219 },
        { "raa215300_a0", .driver_data = (kernel_ulong_t)&config_raa215300_a0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, isl1208_id);

static const __maybe_unused struct of_device_id isl1208_of_match[] = {
        { .compatible = "isil,isl1208", .data = &config_isl1208 },
        { .compatible = "isil,isl1209", .data = &config_isl1209 },
        { .compatible = "isil,isl1218", .data = &config_isl1218 },
        { .compatible = "isil,isl1219", .data = &config_isl1219 },
        { }
};
MODULE_DEVICE_TABLE(of, isl1208_of_match);

/* Device state */
struct isl1208_state {
        struct nvmem_config nvmem_config;
        struct rtc_device *rtc;
        const struct isl1208_config *config;
};

/* block read */
static int
isl1208_i2c_read_regs(struct i2c_client *client, u8 reg, u8 buf[],
                      unsigned len)
{
        int ret;

        WARN_ON(reg > ISL1219_REG_YRT);
        WARN_ON(reg + len > ISL1219_REG_YRT + 1);

        ret = i2c_smbus_read_i2c_block_data(client, reg, len, buf);
        return (ret < 0) ? ret : 0;
}

/* block write */
static int
isl1208_i2c_set_regs(struct i2c_client *client, u8 reg, u8 const buf[],
                     unsigned len)
{
        int ret;

        WARN_ON(reg > ISL1219_REG_YRT);
        WARN_ON(reg + len > ISL1219_REG_YRT + 1);

        ret = i2c_smbus_write_i2c_block_data(client, reg, len, buf);
        return (ret < 0) ? ret : 0;
}

/* simple check to see whether we have a isl1208 */
static int
isl1208_i2c_validate_client(struct i2c_client *client)
{
        u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };
        u8 zero_mask[ISL1208_RTC_SECTION_LEN] = {
                0x80, 0x80, 0x40, 0xc0, 0xe0, 0x00, 0xf8
        };
        int i;
        int ret;

        ret = isl1208_i2c_read_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
        if (ret < 0)
                return ret;

        for (i = 0; i < ISL1208_RTC_SECTION_LEN; ++i) {
                if (regs[i] & zero_mask[i])     /* check if bits are cleared */
                        return -ENODEV;
        }

        return 0;
}

static int isl1208_set_xtoscb(struct i2c_client *client, int sr, int xtosb_val)
{
        /* Do nothing if bit is already set to desired value */
        if (!!(sr & ISL1208_REG_SR_XTOSCB) == xtosb_val)
                return 0;

        if (xtosb_val)
                sr |= ISL1208_REG_SR_XTOSCB;
        else
                sr &= ~ISL1208_REG_SR_XTOSCB;

        return i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
}

static int
isl1208_i2c_get_sr(struct i2c_client *client)
{
        return i2c_smbus_read_byte_data(client, ISL1208_REG_SR);
}

static int
isl1208_i2c_get_atr(struct i2c_client *client)
{
        int atr = i2c_smbus_read_byte_data(client, ISL1208_REG_ATR);
        if (atr < 0)
                return atr;

        /* The 6bit value in the ATR register controls the load
         * capacitance C_load * in steps of 0.25pF
         *
         * bit (1<<5) of the ATR register is inverted
         *
         * C_load(ATR=0x20) =  4.50pF
         * C_load(ATR=0x00) = 12.50pF
         * C_load(ATR=0x1f) = 20.25pF
         *
         */

        atr &= 0x3f;            /* mask out lsb */
        atr ^= 1 << 5;          /* invert 6th bit */
        atr += 2 * 9;           /* add offset of 4.5pF; unit[atr] = 0.25pF */

        return atr;
}

/* returns adjustment value + 100 */
static int
isl1208_i2c_get_dtr(struct i2c_client *client)
{
        int dtr = i2c_smbus_read_byte_data(client, ISL1208_REG_DTR);
        if (dtr < 0)
                return -EIO;

        /* dtr encodes adjustments of {-60,-40,-20,0,20,40,60} ppm */
        dtr = ((dtr & 0x3) * 20) * (dtr & (1 << 2) ? -1 : 1);

        return dtr + 100;
}

static int
isl1208_i2c_get_usr(struct i2c_client *client)
{
        u8 buf[ISL1208_USR_SECTION_LEN] = { 0, };
        int ret;

        ret = isl1208_i2c_read_regs(client, ISL1208_REG_USR1, buf,
                                    ISL1208_USR_SECTION_LEN);
        if (ret < 0)
                return ret;

        return (buf[1] << 8) | buf[0];
}

static int
isl1208_i2c_set_usr(struct i2c_client *client, u16 usr)
{
        u8 buf[ISL1208_USR_SECTION_LEN];

        buf[0] = usr & 0xff;
        buf[1] = (usr >> 8) & 0xff;

        return isl1208_i2c_set_regs(client, ISL1208_REG_USR1, buf,
                                    ISL1208_USR_SECTION_LEN);
}

static int
isl1208_rtc_toggle_alarm(struct i2c_client *client, int enable)
{
        int icr = i2c_smbus_read_byte_data(client, ISL1208_REG_INT);

        if (icr < 0) {
                dev_err(&client->dev, "%s: reading INT failed\n", __func__);
                return icr;
        }

        if (enable)
                icr |= ISL1208_REG_INT_ALME | ISL1208_REG_INT_IM;
        else
                icr &= ~(ISL1208_REG_INT_ALME | ISL1208_REG_INT_IM);

        icr = i2c_smbus_write_byte_data(client, ISL1208_REG_INT, icr);
        if (icr < 0) {
                dev_err(&client->dev, "%s: writing INT failed\n", __func__);
                return icr;
        }

        return 0;
}

static int
isl1208_rtc_proc(struct device *dev, struct seq_file *seq)
{
        struct i2c_client *const client = to_i2c_client(dev);
        int sr, dtr, atr, usr;

        sr = isl1208_i2c_get_sr(client);
        if (sr < 0) {
                dev_err(&client->dev, "%s: reading SR failed\n", __func__);
                return sr;
        }

        seq_printf(seq, "status_reg\t:%s%s%s%s%s%s (0x%.2x)\n",
                   (sr & ISL1208_REG_SR_RTCF) ? " RTCF" : "",
                   (sr & ISL1208_REG_SR_BAT) ? " BAT" : "",
                   (sr & ISL1208_REG_SR_ALM) ? " ALM" : "",
                   (sr & ISL1208_REG_SR_WRTC) ? " WRTC" : "",
                   (sr & ISL1208_REG_SR_XTOSCB) ? " XTOSCB" : "",
                   (sr & ISL1208_REG_SR_ARST) ? " ARST" : "", sr);

        seq_printf(seq, "batt_status\t: %s\n",
                   (sr & ISL1208_REG_SR_RTCF) ? "bad" : "okay");

        dtr = isl1208_i2c_get_dtr(client);
        if (dtr >= 0)
                seq_printf(seq, "digital_trim\t: %d ppm\n", dtr - 100);

        atr = isl1208_i2c_get_atr(client);
        if (atr >= 0)
                seq_printf(seq, "analog_trim\t: %d.%.2d pF\n",
                           atr >> 2, (atr & 0x3) * 25);

        usr = isl1208_i2c_get_usr(client);
        if (usr >= 0)
                seq_printf(seq, "user_data\t: 0x%.4x\n", usr);

        return 0;
}

static int
isl1208_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
{
        int sr;
        u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };

        sr = isl1208_i2c_get_sr(client);
        if (sr < 0) {
                dev_err(&client->dev, "%s: reading SR failed\n", __func__);
                return -EIO;
        }

        sr = isl1208_i2c_read_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
        if (sr < 0) {
                dev_err(&client->dev, "%s: reading RTC section failed\n",
                        __func__);
                return sr;
        }

        tm->tm_sec = bcd2bin(regs[ISL1208_REG_SC]);
        tm->tm_min = bcd2bin(regs[ISL1208_REG_MN]);

        /* HR field has a more complex interpretation */
        {
                const u8 _hr = regs[ISL1208_REG_HR];
                if (_hr & ISL1208_REG_HR_MIL)   /* 24h format */
                        tm->tm_hour = bcd2bin(_hr & 0x3f);
                else {
                        /* 12h format */
                        tm->tm_hour = bcd2bin(_hr & 0x1f);
                        if (_hr & ISL1208_REG_HR_PM)    /* PM flag set */
                                tm->tm_hour += 12;
                }
        }

        tm->tm_mday = bcd2bin(regs[ISL1208_REG_DT]);
        tm->tm_mon = bcd2bin(regs[ISL1208_REG_MO]) - 1; /* rtc starts at 1 */
        tm->tm_year = bcd2bin(regs[ISL1208_REG_YR]) + 100;
        tm->tm_wday = bcd2bin(regs[ISL1208_REG_DW]);

        return 0;
}

static int
isl1208_i2c_read_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
{
        struct rtc_time *const tm = &alarm->time;
        u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
        int icr, yr, sr = isl1208_i2c_get_sr(client);

        if (sr < 0) {
                dev_err(&client->dev, "%s: reading SR failed\n", __func__);
                return sr;
        }

        sr = isl1208_i2c_read_regs(client, ISL1208_REG_SCA, regs,
                                   ISL1208_ALARM_SECTION_LEN);
        if (sr < 0) {
                dev_err(&client->dev, "%s: reading alarm section failed\n",
                        __func__);
                return sr;
        }

        /* MSB of each alarm register is an enable bit */
        tm->tm_sec = bcd2bin(regs[ISL1208_REG_SCA - ISL1208_REG_SCA] & 0x7f);
        tm->tm_min = bcd2bin(regs[ISL1208_REG_MNA - ISL1208_REG_SCA] & 0x7f);
        tm->tm_hour = bcd2bin(regs[ISL1208_REG_HRA - ISL1208_REG_SCA] & 0x3f);
        tm->tm_mday = bcd2bin(regs[ISL1208_REG_DTA - ISL1208_REG_SCA] & 0x3f);
        tm->tm_mon =
                bcd2bin(regs[ISL1208_REG_MOA - ISL1208_REG_SCA] & 0x1f) - 1;
        tm->tm_wday = bcd2bin(regs[ISL1208_REG_DWA - ISL1208_REG_SCA] & 0x03);

        /* The alarm doesn't store the year so get it from the rtc section */
        yr = i2c_smbus_read_byte_data(client, ISL1208_REG_YR);
        if (yr < 0) {
                dev_err(&client->dev, "%s: reading RTC YR failed\n", __func__);
                return yr;
        }
        tm->tm_year = bcd2bin(yr) + 100;

        icr = i2c_smbus_read_byte_data(client, ISL1208_REG_INT);
        if (icr < 0) {
                dev_err(&client->dev, "%s: reading INT failed\n", __func__);
                return icr;
        }
        alarm->enabled = !!(icr & ISL1208_REG_INT_ALME);

        return 0;
}

static int
isl1208_i2c_set_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
{
        struct rtc_time *alarm_tm = &alarm->time;
        u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
        const int offs = ISL1208_REG_SCA;
        struct rtc_time rtc_tm;
        int err, enable;

        err = isl1208_i2c_read_time(client, &rtc_tm);
        if (err)
                return err;

        /* If the alarm time is before the current time disable the alarm */
        if (!alarm->enabled || rtc_tm_sub(alarm_tm, &rtc_tm) <= 0)
                enable = 0x00;
        else
                enable = 0x80;

        /* Program the alarm and enable it for each setting */
        regs[ISL1208_REG_SCA - offs] = bin2bcd(alarm_tm->tm_sec) | enable;
        regs[ISL1208_REG_MNA - offs] = bin2bcd(alarm_tm->tm_min) | enable;
        regs[ISL1208_REG_HRA - offs] = bin2bcd(alarm_tm->tm_hour) |
                ISL1208_REG_HR_MIL | enable;

        regs[ISL1208_REG_DTA - offs] = bin2bcd(alarm_tm->tm_mday) | enable;
        regs[ISL1208_REG_MOA - offs] = bin2bcd(alarm_tm->tm_mon + 1) | enable;
        regs[ISL1208_REG_DWA - offs] = bin2bcd(alarm_tm->tm_wday & 7) | enable;

        /* write ALARM registers */
        err = isl1208_i2c_set_regs(client, offs, regs,
                                  ISL1208_ALARM_SECTION_LEN);
        if (err < 0) {
                dev_err(&client->dev, "%s: writing ALARM section failed\n",
                        __func__);
                return err;
        }

        err = isl1208_rtc_toggle_alarm(client, enable);
        if (err)
                return err;

        return 0;
}

static int
isl1208_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
        return isl1208_i2c_read_time(to_i2c_client(dev), tm);
}

static int
isl1208_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
{
        int sr;
        u8 regs[ISL1208_RTC_SECTION_LEN] = { 0, };

        /* The clock has an 8 bit wide bcd-coded register (they never learn)
         * for the year. tm_year is an offset from 1900 and we are interested
         * in the 2000-2099 range, so any value less than 100 is invalid.
         */
        if (tm->tm_year < 100)
                return -EINVAL;

        regs[ISL1208_REG_SC] = bin2bcd(tm->tm_sec);
        regs[ISL1208_REG_MN] = bin2bcd(tm->tm_min);
        regs[ISL1208_REG_HR] = bin2bcd(tm->tm_hour) | ISL1208_REG_HR_MIL;

        regs[ISL1208_REG_DT] = bin2bcd(tm->tm_mday);
        regs[ISL1208_REG_MO] = bin2bcd(tm->tm_mon + 1);
        regs[ISL1208_REG_YR] = bin2bcd(tm->tm_year - 100);

        regs[ISL1208_REG_DW] = bin2bcd(tm->tm_wday & 7);

        sr = isl1208_i2c_get_sr(client);
        if (sr < 0) {
                dev_err(&client->dev, "%s: reading SR failed\n", __func__);
                return sr;
        }

        /* set WRTC */
        sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR,
                                       sr | ISL1208_REG_SR_WRTC);
        if (sr < 0) {
                dev_err(&client->dev, "%s: writing SR failed\n", __func__);
                return sr;
        }

        /* write RTC registers */
        sr = isl1208_i2c_set_regs(client, 0, regs, ISL1208_RTC_SECTION_LEN);
        if (sr < 0) {
                dev_err(&client->dev, "%s: writing RTC section failed\n",
                        __func__);
                return sr;
        }

        /* clear WRTC again */
        sr = isl1208_i2c_get_sr(client);
        if (sr < 0) {
                dev_err(&client->dev, "%s: reading SR failed\n", __func__);
                return sr;
        }
        sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR,
                                       sr & ~ISL1208_REG_SR_WRTC);
        if (sr < 0) {
                dev_err(&client->dev, "%s: writing SR failed\n", __func__);
                return sr;
        }

        return 0;
}

static int
isl1208_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
        return isl1208_i2c_set_time(to_i2c_client(dev), tm);
}

static int
isl1208_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        return isl1208_i2c_read_alarm(to_i2c_client(dev), alarm);
}

static int
isl1208_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
        return isl1208_i2c_set_alarm(to_i2c_client(dev), alarm);
}

static ssize_t timestamp0_store(struct device *dev,
                                struct device_attribute *attr,
                                const char *buf, size_t count)
{
        struct i2c_client *client = to_i2c_client(dev->parent);
        int sr;

        sr = isl1208_i2c_get_sr(client);
        if (sr < 0) {
                dev_err(dev, "%s: reading SR failed\n", __func__);
                return sr;
        }

        sr &= ~ISL1208_REG_SR_EVT;

        sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
        if (sr < 0)
                dev_err(dev, "%s: writing SR failed\n",
                        __func__);

        return count;
};

static ssize_t timestamp0_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct i2c_client *client = to_i2c_client(dev->parent);
        u8 regs[ISL1219_EVT_SECTION_LEN] = { 0, };
        struct rtc_time tm;
        int sr;

        sr = isl1208_i2c_get_sr(client);
        if (sr < 0) {
                dev_err(dev, "%s: reading SR failed\n", __func__);
                return sr;
        }

        if (!(sr & ISL1208_REG_SR_EVT))
                return 0;

        sr = isl1208_i2c_read_regs(client, ISL1219_REG_SCT, regs,
                                   ISL1219_EVT_SECTION_LEN);
        if (sr < 0) {
                dev_err(dev, "%s: reading event section failed\n",
                        __func__);
                return 0;
        }

        /* MSB of each alarm register is an enable bit */
        tm.tm_sec = bcd2bin(regs[ISL1219_REG_SCT - ISL1219_REG_SCT] & 0x7f);
        tm.tm_min = bcd2bin(regs[ISL1219_REG_MNT - ISL1219_REG_SCT] & 0x7f);
        tm.tm_hour = bcd2bin(regs[ISL1219_REG_HRT - ISL1219_REG_SCT] & 0x3f);
        tm.tm_mday = bcd2bin(regs[ISL1219_REG_DTT - ISL1219_REG_SCT] & 0x3f);
        tm.tm_mon =
                bcd2bin(regs[ISL1219_REG_MOT - ISL1219_REG_SCT] & 0x1f) - 1;
        tm.tm_year = bcd2bin(regs[ISL1219_REG_YRT - ISL1219_REG_SCT]) + 100;

        sr = rtc_valid_tm(&tm);
        if (sr)
                return sr;

        return sprintf(buf, "%llu\n",
                                (unsigned long long)rtc_tm_to_time64(&tm));
};

static DEVICE_ATTR_RW(timestamp0);

static irqreturn_t
isl1208_rtc_interrupt(int irq, void *data)
{
        unsigned long timeout = jiffies + msecs_to_jiffies(1000);
        struct i2c_client *client = data;
        struct isl1208_state *isl1208 = i2c_get_clientdata(client);
        int handled = 0, sr, err;

        if (!isl1208->config->has_tamper) {
                /*
                 * The INT# output is pulled low 250ms after the alarm is
                 * triggered. After the INT# output is pulled low, it is low for
                 * at least 250ms, even if the correct action is taken to clear
                 * it. It is impossible to clear ALM if it is still active. The
                 * host must wait for the RTC to progress past the alarm time
                 * plus the 250ms delay before clearing ALM.
                 */
                msleep(250);
        }

        /*
         * I2C reads get NAK'ed if we read straight away after an interrupt?
         * Using a mdelay/msleep didn't seem to help either, so we work around
         * this by continually trying to read the register for a short time.
         */
        while (1) {
                sr = isl1208_i2c_get_sr(client);
                if (sr >= 0)
                        break;

                if (time_after(jiffies, timeout)) {
                        dev_err(&client->dev, "%s: reading SR failed\n",
                                __func__);
                        return sr;
                }
        }

        if (sr & ISL1208_REG_SR_ALM) {
                dev_dbg(&client->dev, "alarm!\n");

                rtc_update_irq(isl1208->rtc, 1, RTC_IRQF | RTC_AF);

                /* Disable the alarm */
                err = isl1208_rtc_toggle_alarm(client, 0);
                if (err)
                        return err;

                fsleep(275);

                /* Clear the alarm */
                sr &= ~ISL1208_REG_SR_ALM;
                sr = i2c_smbus_write_byte_data(client, ISL1208_REG_SR, sr);
                if (sr < 0)
                        dev_err(&client->dev, "%s: writing SR failed\n",
                                __func__);
                else
                        handled = 1;
        }

        if (isl1208->config->has_tamper && (sr & ISL1208_REG_SR_EVT)) {
                dev_warn(&client->dev, "event detected");
                handled = 1;
                if (isl1208->config->has_timestamp)
                        sysfs_notify(&isl1208->rtc->dev.kobj, NULL,
                                     dev_attr_timestamp0.attr.name);
        }

        return handled ? IRQ_HANDLED : IRQ_NONE;
}

static const struct rtc_class_ops isl1208_rtc_ops = {
        .proc = isl1208_rtc_proc,
        .read_time = isl1208_rtc_read_time,
        .set_time = isl1208_rtc_set_time,
        .read_alarm = isl1208_rtc_read_alarm,
        .set_alarm = isl1208_rtc_set_alarm,
};

/* sysfs interface */

static ssize_t
isl1208_sysfs_show_atrim(struct device *dev,
                         struct device_attribute *attr, char *buf)
{
        int atr = isl1208_i2c_get_atr(to_i2c_client(dev->parent));
        if (atr < 0)
                return atr;

        return sprintf(buf, "%d.%.2d pF\n", atr >> 2, (atr & 0x3) * 25);
}

static DEVICE_ATTR(atrim, S_IRUGO, isl1208_sysfs_show_atrim, NULL);

static ssize_t
isl1208_sysfs_show_dtrim(struct device *dev,
                         struct device_attribute *attr, char *buf)
{
        int dtr = isl1208_i2c_get_dtr(to_i2c_client(dev->parent));
        if (dtr < 0)
                return dtr;

        return sprintf(buf, "%d ppm\n", dtr - 100);
}

static DEVICE_ATTR(dtrim, S_IRUGO, isl1208_sysfs_show_dtrim, NULL);

static ssize_t
isl1208_sysfs_show_usr(struct device *dev,
                       struct device_attribute *attr, char *buf)
{
        int usr = isl1208_i2c_get_usr(to_i2c_client(dev->parent));
        if (usr < 0)
                return usr;

        return sprintf(buf, "0x%.4x\n", usr);
}

static ssize_t
isl1208_sysfs_store_usr(struct device *dev,
                        struct device_attribute *attr,
                        const char *buf, size_t count)
{
        int usr = -1;

        if (buf[0] == '0' && (buf[1] == 'x' || buf[1] == 'X')) {
                if (sscanf(buf, "%x", &usr) != 1)
                        return -EINVAL;
        } else {
                if (sscanf(buf, "%d", &usr) != 1)
                        return -EINVAL;
        }

        if (usr < 0 || usr > 0xffff)
                return -EINVAL;

        if (isl1208_i2c_set_usr(to_i2c_client(dev->parent), usr))
                return -EIO;

        return count;
}

static DEVICE_ATTR(usr, S_IRUGO | S_IWUSR, isl1208_sysfs_show_usr,
                   isl1208_sysfs_store_usr);

static struct attribute *isl1208_rtc_attrs[] = {
        &dev_attr_atrim.attr,
        &dev_attr_dtrim.attr,
        &dev_attr_usr.attr,
        NULL
};

static const struct attribute_group isl1208_rtc_sysfs_files = {
        .attrs  = isl1208_rtc_attrs,
};

static struct attribute *isl1219_rtc_attrs[] = {
        &dev_attr_timestamp0.attr,
        NULL
};

static const struct attribute_group isl1219_rtc_sysfs_files = {
        .attrs  = isl1219_rtc_attrs,
};

static int isl1208_nvmem_read(void *priv, unsigned int off, void *buf,
                              size_t count)
{
        struct isl1208_state *isl1208 = priv;
        struct i2c_client *client = to_i2c_client(isl1208->rtc->dev.parent);

        /* nvmem sanitizes offset/count for us, but count==0 is possible */
        if (!count)
                return count;

        return isl1208_i2c_read_regs(client, ISL1208_REG_USR1 + off, buf,
                                    count);
}

static int isl1208_nvmem_write(void *priv, unsigned int off, void *buf,
                               size_t count)
{
        struct isl1208_state *isl1208 = priv;
        struct i2c_client *client = to_i2c_client(isl1208->rtc->dev.parent);

        /* nvmem sanitizes off/count for us, but count==0 is possible */
        if (!count)
                return count;

        return isl1208_i2c_set_regs(client, ISL1208_REG_USR1 + off, buf,
                                   count);
}

static const struct nvmem_config isl1208_nvmem_config = {
        .name = "isl1208_nvram",
        .word_size = 1,
        .stride = 1,
        /* .size from chip specific config */
        .reg_read = isl1208_nvmem_read,
        .reg_write = isl1208_nvmem_write,
};

static int isl1208_setup_irq(struct i2c_client *client, int irq)
{
        int rc = devm_request_threaded_irq(&client->dev, irq, NULL,
                                        isl1208_rtc_interrupt,
                                        IRQF_SHARED | IRQF_ONESHOT,
                                        isl1208_driver.driver.name,
                                        client);
        if (!rc) {
                device_init_wakeup(&client->dev, true);
                enable_irq_wake(irq);
        } else {
                dev_err(&client->dev,
                        "Unable to request irq %d, no alarm support\n",
                        irq);
        }
        return rc;
}

static int
isl1208_clk_present(struct i2c_client *client, const char *name)
{
        struct clk *clk;

        clk = devm_clk_get_optional(&client->dev, name);
        if (IS_ERR(clk))
                return PTR_ERR(clk);

        return !!clk;
}

static int
isl1208_probe(struct i2c_client *client)
{
        struct isl1208_state *isl1208;
        int evdet_irq = -1;
        int xtosb_val = 0;
        int rc = 0;
        int sr;

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

        if (isl1208_i2c_validate_client(client) < 0)
                return -ENODEV;

        /* Allocate driver state, point i2c client data to it */
        isl1208 = devm_kzalloc(&client->dev, sizeof(*isl1208), GFP_KERNEL);
        if (!isl1208)
                return -ENOMEM;
        i2c_set_clientdata(client, isl1208);

        /* Determine which chip we have */
        isl1208->config = i2c_get_match_data(client);
        if (!isl1208->config)
                return -ENODEV;

        rc = isl1208_clk_present(client, "xin");
        if (rc < 0)
                return rc;

        if (!rc) {
                rc = isl1208_clk_present(client, "clkin");
                if (rc < 0)
                        return rc;

                if (rc)
                        xtosb_val = 1;
        }

        isl1208->rtc = devm_rtc_allocate_device(&client->dev);
        if (IS_ERR(isl1208->rtc))
                return PTR_ERR(isl1208->rtc);

        isl1208->rtc->ops = &isl1208_rtc_ops;

        /* Setup nvmem configuration in driver state struct */
        isl1208->nvmem_config = isl1208_nvmem_config;
        isl1208->nvmem_config.size = isl1208->config->nvmem_length;
        isl1208->nvmem_config.priv = isl1208;

        sr = isl1208_i2c_get_sr(client);
        if (sr < 0) {
                dev_err(&client->dev, "reading status failed\n");
                return sr;
        }

        if (isl1208->config->has_inverted_osc_bit)
                xtosb_val = !xtosb_val;

        rc = isl1208_set_xtoscb(client, sr, xtosb_val);
        if (rc)
                return rc;

        if (sr & ISL1208_REG_SR_RTCF)
                dev_warn(&client->dev, "rtc power failure detected, "
                         "please set clock.\n");

        if (isl1208->config->has_tamper) {
                struct device_node *np = client->dev.of_node;
                u32 evienb;

                rc = i2c_smbus_read_byte_data(client, ISL1219_REG_EV);
                if (rc < 0) {
                        dev_err(&client->dev, "failed to read EV reg\n");
                        return rc;
                }
                rc |= ISL1219_REG_EV_EVEN;
                if (!of_property_read_u32(np, "isil,ev-evienb", &evienb)) {
                        if (evienb)
                                rc |= ISL1219_REG_EV_EVIENB;
                        else
                                rc &= ~ISL1219_REG_EV_EVIENB;
                }
                rc = i2c_smbus_write_byte_data(client, ISL1219_REG_EV, rc);
                if (rc < 0) {
                        dev_err(&client->dev, "could not enable tamper detection\n");
                        return rc;
                }
                evdet_irq = of_irq_get_byname(np, "evdet");
        }
        if (isl1208->config->has_timestamp) {
                rc = rtc_add_group(isl1208->rtc, &isl1219_rtc_sysfs_files);
                if (rc)
                        return rc;
        }

        rc = rtc_add_group(isl1208->rtc, &isl1208_rtc_sysfs_files);
        if (rc)
                return rc;

        if (client->irq > 0) {
                rc = isl1208_setup_irq(client, client->irq);
                if (rc)
                        return rc;
        } else {
                clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, isl1208->rtc->features);
        }

        if (evdet_irq > 0 && evdet_irq != client->irq)
                rc = isl1208_setup_irq(client, evdet_irq);
        if (rc)
                return rc;

        rc = devm_rtc_nvmem_register(isl1208->rtc, &isl1208->nvmem_config);
        if (rc)
                return rc;

        return devm_rtc_register_device(isl1208->rtc);
}

static struct i2c_driver isl1208_driver = {
        .driver = {
                .name = "rtc-isl1208",
                .of_match_table = of_match_ptr(isl1208_of_match),
        },
        .probe = isl1208_probe,
        .id_table = isl1208_id,
};

module_i2c_driver(isl1208_driver);

MODULE_AUTHOR("Herbert Valerio Riedel <hvr@gnu.org>");
MODULE_DESCRIPTION("Intersil ISL1208 RTC driver");
MODULE_LICENSE("GPL");