// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * STTS751 sensor driver
 *
 * Copyright (C) 2016-2017 Istituto Italiano di Tecnologia - RBCS - EDL
 * Robotics, Brain and Cognitive Sciences department
 * Electronic Design Laboratory
 *
 * Written by Andrea Merello <andrea.merello@gmail.com>
 *
 * Based on  LM95241 driver and LM90 driver
 */

#include <linux/bitops.h>
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/util_macros.h>

#define DEVNAME "stts751"

static const unsigned short normal_i2c[] = {
        0x48, 0x49, 0x38, 0x39,  /* STTS751-0 */
        0x4A, 0x4B, 0x3A, 0x3B,  /* STTS751-1 */
        I2C_CLIENT_END };

#define STTS751_REG_TEMP_H      0x00
#define STTS751_REG_STATUS      0x01
#define STTS751_STATUS_TRIPT    BIT(0)
#define STTS751_STATUS_TRIPL    BIT(5)
#define STTS751_STATUS_TRIPH    BIT(6)
#define STTS751_REG_TEMP_L      0x02
#define STTS751_REG_CONF        0x03
#define STTS751_CONF_RES_MASK   0x0C
#define STTS751_CONF_RES_SHIFT  2
#define STTS751_CONF_EVENT_DIS  BIT(7)
#define STTS751_CONF_STOP       BIT(6)
#define STTS751_REG_RATE        0x04
#define STTS751_REG_HLIM_H      0x05
#define STTS751_REG_HLIM_L      0x06
#define STTS751_REG_LLIM_H      0x07
#define STTS751_REG_LLIM_L      0x08
#define STTS751_REG_TLIM        0x20
#define STTS751_REG_HYST        0x21
#define STTS751_REG_SMBUS_TO    0x22

#define STTS751_REG_PROD_ID     0xFD
#define STTS751_REG_MAN_ID      0xFE
#define STTS751_REG_REV_ID      0xFF

#define STTS751_0_PROD_ID       0x00
#define STTS751_1_PROD_ID       0x01
#define ST_MAN_ID               0x53

/*
 * Possible update intervals are (in mS):
 * 16000, 8000, 4000, 2000, 1000, 500, 250, 125, 62.5, 31.25
 * However we are not going to complicate things too much and we stick to the
 * approx value in mS.
 */
static const int stts751_intervals[] = {
        16000, 8000, 4000, 2000, 1000, 500, 250, 125, 63, 31
};

static const struct i2c_device_id stts751_id[] = {
        { "stts751", 0 },
        { }
};

static const struct of_device_id __maybe_unused stts751_of_match[] = {
        { .compatible = "stts751" },
        { },
};
MODULE_DEVICE_TABLE(of, stts751_of_match);

struct stts751_priv {
        struct device *dev;
        struct i2c_client *client;
        struct mutex access_lock;
        u8 interval;
        int res;
        int event_max, event_min;
        int therm;
        int hyst;
        bool smbus_timeout;
        int temp;
        unsigned long last_update, last_alert_update;
        u8 config;
        bool min_alert, max_alert, therm_trip;
        bool data_valid, alert_valid;
        bool notify_max, notify_min;
};

/*
 * These functions converts temperature from HW format to integer format and
 * vice-vers. They are (mostly) taken from lm90 driver. Unit is in mC.
 */
static int stts751_to_deg(s16 hw_val)
{
        return hw_val * 125 / 32;
}

static s32 stts751_to_hw(int val)
{
        return DIV_ROUND_CLOSEST(val, 125) * 32;
}

static int stts751_adjust_resolution(struct stts751_priv *priv)
{
        u8 res;

        switch (priv->interval) {
        case 9:
                /* 10 bits */
                res = 0;
                break;
        case 8:
                /* 11 bits */
                res = 1;
                break;
        default:
                /* 12 bits */
                res = 3;
                break;
        }

        if (priv->res == res)
                return 0;

        priv->config &= ~STTS751_CONF_RES_MASK;
        priv->config |= res << STTS751_CONF_RES_SHIFT;
        dev_dbg(&priv->client->dev, "setting res %d. config %x",
                res, priv->config);
        priv->res = res;

        return i2c_smbus_write_byte_data(priv->client,
                                STTS751_REG_CONF, priv->config);
}

static int stts751_update_temp(struct stts751_priv *priv)
{
        s32 integer1, integer2, frac;

        /*
         * There is a trick here, like in the lm90 driver. We have to read two
         * registers to get the sensor temperature, but we have to beware a
         * conversion could occur between the readings. We could use the
         * one-shot conversion register, but we don't want to do this (disables
         * hardware monitoring). So the solution used here is to read the high
         * byte once, then the low byte, then the high byte again. If the new
         * high byte matches the old one, then we have a valid reading. Else we
         * have to read the low byte again, and now we believe we have a correct
         * reading.
         */
        integer1 = i2c_smbus_read_byte_data(priv->client, STTS751_REG_TEMP_H);
        if (integer1 < 0) {
                dev_dbg(&priv->client->dev,
                        "I2C read failed (temp H). ret: %x\n", integer1);
                return integer1;
        }

        frac = i2c_smbus_read_byte_data(priv->client, STTS751_REG_TEMP_L);
        if (frac < 0) {
                dev_dbg(&priv->client->dev,
                        "I2C read failed (temp L). ret: %x\n", frac);
                return frac;
        }

        integer2 = i2c_smbus_read_byte_data(priv->client, STTS751_REG_TEMP_H);
        if (integer2 < 0) {
                dev_dbg(&priv->client->dev,
                        "I2C 2nd read failed (temp H). ret: %x\n", integer2);
                return integer2;
        }

        if (integer1 != integer2) {
                frac = i2c_smbus_read_byte_data(priv->client,
                                                STTS751_REG_TEMP_L);
                if (frac < 0) {
                        dev_dbg(&priv->client->dev,
                                "I2C 2nd read failed (temp L). ret: %x\n",
                                frac);
                        return frac;
                }
        }

        priv->temp = stts751_to_deg((integer1 << 8) | frac);
        return 0;
}

static int stts751_set_temp_reg16(struct stts751_priv *priv, int temp,
                                  u8 hreg, u8 lreg)
{
        s32 hwval;
        int ret;

        hwval = stts751_to_hw(temp);

        ret = i2c_smbus_write_byte_data(priv->client, hreg, hwval >> 8);
        if (ret)
                return ret;

        return i2c_smbus_write_byte_data(priv->client, lreg, hwval & 0xff);
}

static int stts751_set_temp_reg8(struct stts751_priv *priv, int temp, u8 reg)
{
        s32 hwval;

        hwval = stts751_to_hw(temp);
        return i2c_smbus_write_byte_data(priv->client, reg, hwval >> 8);
}

static int stts751_read_reg16(struct stts751_priv *priv, int *temp,
                              u8 hreg, u8 lreg)
{
        int integer, frac;

        integer = i2c_smbus_read_byte_data(priv->client, hreg);
        if (integer < 0)
                return integer;

        frac = i2c_smbus_read_byte_data(priv->client, lreg);
        if (frac < 0)
                return frac;

        *temp = stts751_to_deg((integer << 8) | frac);

        return 0;
}

static int stts751_read_reg8(struct stts751_priv *priv, int *temp, u8 reg)
{
        int integer;

        integer = i2c_smbus_read_byte_data(priv->client, reg);
        if (integer < 0)
                return integer;

        *temp = stts751_to_deg(integer << 8);

        return 0;
}

/*
 * Update alert flags without waiting for cache to expire. We detects alerts
 * immediately for the sake of the alert handler; we still need to deal with
 * caching to workaround the fact that alarm flags int the status register,
 * despite what the datasheet claims, gets always cleared on read.
 */
static int stts751_update_alert(struct stts751_priv *priv)
{
        int ret;
        bool conv_done;
        int cache_time = msecs_to_jiffies(stts751_intervals[priv->interval]);

        /*
         * Add another 10% because if we run faster than the HW conversion
         * rate we will end up in reporting incorrectly alarms.
         */
        cache_time += cache_time / 10;

        ret = i2c_smbus_read_byte_data(priv->client, STTS751_REG_STATUS);
        if (ret < 0)
                return ret;

        dev_dbg(&priv->client->dev, "status reg %x\n", ret);
        conv_done = ret & (STTS751_STATUS_TRIPH | STTS751_STATUS_TRIPL);
        /*
         * Reset the cache if the cache time expired, or if we are sure
         * we have valid data from a device conversion, or if we know
         * our cache has been never written.
         *
         * Note that when the cache has been never written the point is
         * to correctly initialize the timestamp, rather than clearing
         * the cache values.
         *
         * Note that updating the cache timestamp when we get an alarm flag
         * is required, otherwise we could incorrectly report alarms to be zero.
         */
        if (time_after(jiffies, priv->last_alert_update + cache_time) ||
            conv_done || !priv->alert_valid) {
                priv->max_alert = false;
                priv->min_alert = false;
                priv->alert_valid = true;
                priv->last_alert_update = jiffies;
                dev_dbg(&priv->client->dev, "invalidating alert cache\n");
        }

        priv->max_alert |= !!(ret & STTS751_STATUS_TRIPH);
        priv->min_alert |= !!(ret & STTS751_STATUS_TRIPL);
        priv->therm_trip = !!(ret & STTS751_STATUS_TRIPT);

        dev_dbg(&priv->client->dev, "max_alert: %d, min_alert: %d, therm_trip: %d\n",
                priv->max_alert, priv->min_alert, priv->therm_trip);

        return 0;
}

static void stts751_alert(struct i2c_client *client,
                          enum i2c_alert_protocol type, unsigned int data)
{
        int ret;
        struct stts751_priv *priv = i2c_get_clientdata(client);

        if (type != I2C_PROTOCOL_SMBUS_ALERT)
                return;

        dev_dbg(&client->dev, "alert!");

        mutex_lock(&priv->access_lock);
        ret = stts751_update_alert(priv);
        if (ret < 0) {
                /* default to worst case */
                priv->max_alert = true;
                priv->min_alert = true;

                dev_warn(priv->dev,
                         "Alert received, but can't communicate to the device. Triggering all alarms!");
        }

        if (priv->max_alert) {
                if (priv->notify_max)
                        dev_notice(priv->dev, "got alert for HIGH temperature");
                priv->notify_max = false;

                /* unblock alert poll */
                sysfs_notify(&priv->dev->kobj, NULL, "temp1_max_alarm");
        }

        if (priv->min_alert) {
                if (priv->notify_min)
                        dev_notice(priv->dev, "got alert for LOW temperature");
                priv->notify_min = false;

                /* unblock alert poll */
                sysfs_notify(&priv->dev->kobj, NULL, "temp1_min_alarm");
        }

        if (priv->min_alert || priv->max_alert)
                kobject_uevent(&priv->dev->kobj, KOBJ_CHANGE);

        mutex_unlock(&priv->access_lock);
}

static int stts751_update(struct stts751_priv *priv)
{
        int ret;
        int cache_time = msecs_to_jiffies(stts751_intervals[priv->interval]);

        if (time_after(jiffies, priv->last_update + cache_time) ||
            !priv->data_valid) {
                ret = stts751_update_temp(priv);
                if (ret)
                        return ret;

                ret = stts751_update_alert(priv);
                if (ret)
                        return ret;
                priv->data_valid = true;
                priv->last_update = jiffies;
        }

        return 0;
}

static ssize_t max_alarm_show(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        int ret;
        struct stts751_priv *priv = dev_get_drvdata(dev);

        mutex_lock(&priv->access_lock);
        ret = stts751_update(priv);
        if (!ret)
                priv->notify_max = true;
        mutex_unlock(&priv->access_lock);
        if (ret < 0)
                return ret;

        return sysfs_emit(buf, "%d\n", priv->max_alert);
}

static ssize_t min_alarm_show(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        int ret;
        struct stts751_priv *priv = dev_get_drvdata(dev);

        mutex_lock(&priv->access_lock);
        ret = stts751_update(priv);
        if (!ret)
                priv->notify_min = true;
        mutex_unlock(&priv->access_lock);
        if (ret < 0)
                return ret;

        return sysfs_emit(buf, "%d\n", priv->min_alert);
}

static ssize_t input_show(struct device *dev, struct device_attribute *attr,
                          char *buf)
{
        int ret;
        struct stts751_priv *priv = dev_get_drvdata(dev);

        mutex_lock(&priv->access_lock);
        ret = stts751_update(priv);
        mutex_unlock(&priv->access_lock);
        if (ret < 0)
                return ret;

        return sysfs_emit(buf, "%d\n", priv->temp);
}

static ssize_t therm_show(struct device *dev, struct device_attribute *attr,
                          char *buf)
{
        struct stts751_priv *priv = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%d\n", priv->therm);
}

static ssize_t therm_store(struct device *dev, struct device_attribute *attr,
                           const char *buf, size_t count)
{
        int ret;
        long temp;
        struct stts751_priv *priv = dev_get_drvdata(dev);

        if (kstrtol(buf, 10, &temp) < 0)
                return -EINVAL;

        /* HW works in range -64C to +127.937C */
        temp = clamp_val(temp, -64000, 127937);
        mutex_lock(&priv->access_lock);
        ret = stts751_set_temp_reg8(priv, temp, STTS751_REG_TLIM);
        if (ret)
                goto exit;

        dev_dbg(&priv->client->dev, "setting therm %ld", temp);

        /*
         * hysteresis reg is relative to therm, so the HW does not need to be
         * adjusted, we need to update our local copy only.
         */
        priv->hyst = temp - (priv->therm - priv->hyst);
        priv->therm = temp;

exit:
        mutex_unlock(&priv->access_lock);
        if (ret)
                return ret;

        return count;
}

static ssize_t hyst_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct stts751_priv *priv = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%d\n", priv->hyst);
}

static ssize_t hyst_store(struct device *dev, struct device_attribute *attr,
                          const char *buf, size_t count)
{
        int ret;
        long temp;

        struct stts751_priv *priv = dev_get_drvdata(dev);

        if (kstrtol(buf, 10, &temp) < 0)
                return -EINVAL;

        mutex_lock(&priv->access_lock);
        /* HW works in range -64C to +127.937C */
        temp = clamp_val(temp, -64000, priv->therm);
        priv->hyst = temp;
        dev_dbg(&priv->client->dev, "setting hyst %ld", temp);
        temp = priv->therm - temp;
        ret = stts751_set_temp_reg8(priv, temp, STTS751_REG_HYST);
        mutex_unlock(&priv->access_lock);
        if (ret)
                return ret;

        return count;
}

static ssize_t therm_trip_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        int ret;
        struct stts751_priv *priv = dev_get_drvdata(dev);

        mutex_lock(&priv->access_lock);
        ret = stts751_update(priv);
        mutex_unlock(&priv->access_lock);
        if (ret < 0)
                return ret;

        return sysfs_emit(buf, "%d\n", priv->therm_trip);
}

static ssize_t max_show(struct device *dev, struct device_attribute *attr,
                        char *buf)
{
        struct stts751_priv *priv = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%d\n", priv->event_max);
}

static ssize_t max_store(struct device *dev, struct device_attribute *attr,
                         const char *buf, size_t count)
{
        int ret;
        long temp;
        struct stts751_priv *priv = dev_get_drvdata(dev);

        if (kstrtol(buf, 10, &temp) < 0)
                return -EINVAL;

        mutex_lock(&priv->access_lock);
        /* HW works in range -64C to +127.937C */
        temp = clamp_val(temp, priv->event_min, 127937);
        ret = stts751_set_temp_reg16(priv, temp,
                                     STTS751_REG_HLIM_H, STTS751_REG_HLIM_L);
        if (ret)
                goto exit;

        dev_dbg(&priv->client->dev, "setting event max %ld", temp);
        priv->event_max = temp;
        ret = count;
exit:
        mutex_unlock(&priv->access_lock);
        return ret;
}

static ssize_t min_show(struct device *dev, struct device_attribute *attr,
                        char *buf)
{
        struct stts751_priv *priv = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%d\n", priv->event_min);
}

static ssize_t min_store(struct device *dev, struct device_attribute *attr,
                         const char *buf, size_t count)
{
        int ret;
        long temp;
        struct stts751_priv *priv = dev_get_drvdata(dev);

        if (kstrtol(buf, 10, &temp) < 0)
                return -EINVAL;

        mutex_lock(&priv->access_lock);
        /* HW works in range -64C to +127.937C */
        temp = clamp_val(temp, -64000, priv->event_max);
        ret = stts751_set_temp_reg16(priv, temp,
                                     STTS751_REG_LLIM_H, STTS751_REG_LLIM_L);
        if (ret)
                goto exit;

        dev_dbg(&priv->client->dev, "setting event min %ld", temp);
        priv->event_min = temp;
        ret = count;
exit:
        mutex_unlock(&priv->access_lock);
        return ret;
}

static ssize_t interval_show(struct device *dev,
                             struct device_attribute *attr, char *buf)
{
        struct stts751_priv *priv = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%d\n",
                          stts751_intervals[priv->interval]);
}

static ssize_t interval_store(struct device *dev,
                              struct device_attribute *attr, const char *buf,
                              size_t count)
{
        unsigned long val;
        int idx;
        int ret = count;
        struct stts751_priv *priv = dev_get_drvdata(dev);

        if (kstrtoul(buf, 10, &val) < 0)
                return -EINVAL;

        idx = find_closest_descending(val, stts751_intervals,
                                      ARRAY_SIZE(stts751_intervals));

        dev_dbg(&priv->client->dev, "setting interval. req:%lu, idx: %d, val: %d",
                val, idx, stts751_intervals[idx]);

        mutex_lock(&priv->access_lock);
        if (priv->interval == idx)
                goto exit;

        /*
         * In early development stages I've become suspicious about the chip
         * starting to misbehave if I ever set, even briefly, an invalid
         * configuration. While I'm not sure this is really needed, be
         * conservative and set rate/resolution in such an order that avoids
         * passing through an invalid configuration.
         */

        /* speed up: lower the resolution, then modify convrate */
        if (priv->interval < idx) {
                dev_dbg(&priv->client->dev, "lower resolution, then modify convrate");
                priv->interval = idx;
                ret = stts751_adjust_resolution(priv);
                if (ret)
                        goto exit;
        }

        ret = i2c_smbus_write_byte_data(priv->client, STTS751_REG_RATE, idx);
        if (ret)
                goto exit;
        /* slow down: modify convrate, then raise resolution */
        if (priv->interval != idx) {
                dev_dbg(&priv->client->dev, "modify convrate, then raise resolution");
                priv->interval = idx;
                ret = stts751_adjust_resolution(priv);
                if (ret)
                        goto exit;
        }
        ret = count;
exit:
        mutex_unlock(&priv->access_lock);

        return ret;
}

static int stts751_detect(struct i2c_client *new_client,
                          struct i2c_board_info *info)
{
        struct i2c_adapter *adapter = new_client->adapter;
        const char *name;
        int tmp;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
                return -ENODEV;

        tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_MAN_ID);
        if (tmp != ST_MAN_ID)
                return -ENODEV;

        /* lower temperaure registers always have bits 0-3 set to zero */
        tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_TEMP_L);
        if (tmp & 0xf)
                return -ENODEV;

        tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_HLIM_L);
        if (tmp & 0xf)
                return -ENODEV;

        tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_LLIM_L);
        if (tmp & 0xf)
                return -ENODEV;

        /* smbus timeout register always have bits 0-7 set to zero */
        tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_SMBUS_TO);
        if (tmp & 0x7f)
                return -ENODEV;

        tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_PROD_ID);

        switch (tmp) {
        case STTS751_0_PROD_ID:
                name = "STTS751-0";
                break;
        case STTS751_1_PROD_ID:
                name = "STTS751-1";
                break;
        default:
                return -ENODEV;
        }
        dev_dbg(&new_client->dev, "Chip %s detected", name);

        strlcpy(info->type, stts751_id[0].name, I2C_NAME_SIZE);
        return 0;
}

static int stts751_read_chip_config(struct stts751_priv *priv)
{
        int ret;
        int tmp;

        ret = i2c_smbus_read_byte_data(priv->client, STTS751_REG_CONF);
        if (ret < 0)
                return ret;
        priv->config = ret;
        priv->res = (ret & STTS751_CONF_RES_MASK) >> STTS751_CONF_RES_SHIFT;

        ret = i2c_smbus_read_byte_data(priv->client, STTS751_REG_RATE);
        if (ret < 0)
                return ret;
        if (ret >= ARRAY_SIZE(stts751_intervals)) {
                dev_err(priv->dev, "Unrecognized conversion rate 0x%x\n", ret);
                return -ENODEV;
        }
        priv->interval = ret;

        ret = stts751_read_reg16(priv, &priv->event_max,
                                 STTS751_REG_HLIM_H, STTS751_REG_HLIM_L);
        if (ret)
                return ret;

        ret = stts751_read_reg16(priv, &priv->event_min,
                                 STTS751_REG_LLIM_H, STTS751_REG_LLIM_L);
        if (ret)
                return ret;

        ret = stts751_read_reg8(priv, &priv->therm, STTS751_REG_TLIM);
        if (ret)
                return ret;

        ret = stts751_read_reg8(priv, &tmp, STTS751_REG_HYST);
        if (ret)
                return ret;
        priv->hyst = priv->therm - tmp;

        return 0;
}

static SENSOR_DEVICE_ATTR_RO(temp1_input, input, 0);
static SENSOR_DEVICE_ATTR_RW(temp1_min, min, 0);
static SENSOR_DEVICE_ATTR_RW(temp1_max, max, 0);
static SENSOR_DEVICE_ATTR_RO(temp1_min_alarm, min_alarm, 0);
static SENSOR_DEVICE_ATTR_RO(temp1_max_alarm, max_alarm, 0);
static SENSOR_DEVICE_ATTR_RW(temp1_crit, therm, 0);
static SENSOR_DEVICE_ATTR_RW(temp1_crit_hyst, hyst, 0);
static SENSOR_DEVICE_ATTR_RO(temp1_crit_alarm, therm_trip, 0);
static SENSOR_DEVICE_ATTR_RW(update_interval, interval, 0);

static struct attribute *stts751_attrs[] = {
        &sensor_dev_attr_temp1_input.dev_attr.attr,
        &sensor_dev_attr_temp1_min.dev_attr.attr,
        &sensor_dev_attr_temp1_max.dev_attr.attr,
        &sensor_dev_attr_temp1_min_alarm.dev_attr.attr,
        &sensor_dev_attr_temp1_max_alarm.dev_attr.attr,
        &sensor_dev_attr_temp1_crit.dev_attr.attr,
        &sensor_dev_attr_temp1_crit_hyst.dev_attr.attr,
        &sensor_dev_attr_temp1_crit_alarm.dev_attr.attr,
        &sensor_dev_attr_update_interval.dev_attr.attr,
        NULL
};
ATTRIBUTE_GROUPS(stts751);

static int stts751_probe(struct i2c_client *client)
{
        struct stts751_priv *priv;
        int ret;
        bool smbus_nto;
        int rev_id;

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

        priv->client = client;
        priv->notify_max = true;
        priv->notify_min = true;
        i2c_set_clientdata(client, priv);
        mutex_init(&priv->access_lock);

        if (device_property_present(&client->dev,
                                    "smbus-timeout-disable")) {
                smbus_nto = device_property_read_bool(&client->dev,
                                                      "smbus-timeout-disable");

                ret = i2c_smbus_write_byte_data(client, STTS751_REG_SMBUS_TO,
                                                smbus_nto ? 0 : 0x80);
                if (ret)
                        return ret;
        }

        rev_id = i2c_smbus_read_byte_data(client, STTS751_REG_REV_ID);
        if (rev_id < 0)
                return -ENODEV;
        if (rev_id != 0x1) {
                dev_dbg(&client->dev, "Chip revision 0x%x is untested\n",
                        rev_id);
        }

        ret = stts751_read_chip_config(priv);
        if (ret)
                return ret;

        priv->config &= ~(STTS751_CONF_STOP | STTS751_CONF_EVENT_DIS);
        ret = i2c_smbus_write_byte_data(client, STTS751_REG_CONF, priv->config);
        if (ret)
                return ret;

        priv->dev = devm_hwmon_device_register_with_groups(&client->dev,
                                                        client->name, priv,
                                                        stts751_groups);
        return PTR_ERR_OR_ZERO(priv->dev);
}

MODULE_DEVICE_TABLE(i2c, stts751_id);

static struct i2c_driver stts751_driver = {
        .class          = I2C_CLASS_HWMON,
        .driver = {
                .name   = DEVNAME,
                .of_match_table = of_match_ptr(stts751_of_match),
        },
        .probe_new      = stts751_probe,
        .id_table       = stts751_id,
        .detect         = stts751_detect,
        .alert          = stts751_alert,
        .address_list   = normal_i2c,
};

module_i2c_driver(stts751_driver);

MODULE_AUTHOR("Andrea Merello <andrea.merello@gmail.com>");
MODULE_DESCRIPTION("STTS751 sensor driver");
MODULE_LICENSE("GPL");