// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * An hwmon driver for the Microchip TC74
 *
 * Copyright 2015 Maciej Szmigiero <mail@maciej.szmigiero.name>
 *
 * Based on ad7414.c:
 *      Copyright 2006 Stefan Roese, DENX Software Engineering
 *      Copyright 2008 Sean MacLennan, PIKA Technologies
 *      Copyright 2008 Frank Edelhaeuser, Spansion Inc.
 */

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

/* TC74 registers */
#define TC74_REG_TEMP           0x00
#define TC74_REG_CONFIG         0x01

struct tc74_data {
        struct i2c_client       *client;
        struct mutex            lock;   /* atomic read data updates */
        bool                    valid;  /* validity of fields below */
        unsigned long           next_update;    /* In jiffies */
        s8                      temp_input;     /* Temp value in dC */
};

static int tc74_update_device(struct device *dev)
{
        struct tc74_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        int ret;

        ret = mutex_lock_interruptible(&data->lock);
        if (ret)
                return ret;

        if (time_after(jiffies, data->next_update) || !data->valid) {
                s32 value;

                value = i2c_smbus_read_byte_data(client, TC74_REG_CONFIG);
                if (value < 0) {
                        dev_dbg(&client->dev, "TC74_REG_CONFIG read err %d\n",
                                (int)value);

                        ret = value;
                        goto ret_unlock;
                }

                if (!(value & BIT(6))) {
                        /* not ready yet */

                        ret = -EAGAIN;
                        goto ret_unlock;
                }

                value = i2c_smbus_read_byte_data(client, TC74_REG_TEMP);
                if (value < 0) {
                        dev_dbg(&client->dev, "TC74_REG_TEMP read err %d\n",
                                (int)value);

                        ret = value;
                        goto ret_unlock;
                }

                data->temp_input = value;
                data->next_update = jiffies + HZ / 4;
                data->valid = true;
        }

ret_unlock:
        mutex_unlock(&data->lock);

        return ret;
}

static ssize_t temp_input_show(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct tc74_data *data = dev_get_drvdata(dev);
        int ret;

        ret = tc74_update_device(dev);
        if (ret)
                return ret;

        return sprintf(buf, "%d\n", data->temp_input * 1000);
}
static SENSOR_DEVICE_ATTR_RO(temp1_input, temp_input, 0);

static struct attribute *tc74_attrs[] = {
        &sensor_dev_attr_temp1_input.dev_attr.attr,
        NULL
};

ATTRIBUTE_GROUPS(tc74);

static int tc74_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct tc74_data *data;
        struct device *hwmon_dev;
        s32 conf;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
                return -EOPNOTSUPP;

        data = devm_kzalloc(dev, sizeof(struct tc74_data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->client = client;
        mutex_init(&data->lock);

        /* Make sure the chip is powered up. */
        conf = i2c_smbus_read_byte_data(client, TC74_REG_CONFIG);
        if (conf < 0) {
                dev_err(dev, "unable to read config register\n");

                return conf;
        }

        if (conf & 0x3f) {
                dev_err(dev, "invalid config register value\n");

                return -ENODEV;
        }

        if (conf & BIT(7)) {
                s32 ret;

                conf &= ~BIT(7);

                ret = i2c_smbus_write_byte_data(client, TC74_REG_CONFIG, conf);
                if (ret)
                        dev_warn(dev, "unable to disable STANDBY\n");
        }

        hwmon_dev = devm_hwmon_device_register_with_groups(dev,
                                                           client->name,
                                                           data, tc74_groups);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id tc74_id[] = {
        { "tc74" },
        {}
};
MODULE_DEVICE_TABLE(i2c, tc74_id);

static struct i2c_driver tc74_driver = {
        .driver = {
                .name   = "tc74",
        },
        .probe = tc74_probe,
        .id_table = tc74_id,
};

module_i2c_driver(tc74_driver);

MODULE_AUTHOR("Maciej Szmigiero <mail@maciej.szmigiero.name>");

MODULE_DESCRIPTION("TC74 driver");
MODULE_LICENSE("GPL");