// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * This is a non-complete driver implementation for the
 * HS3001 humidity and temperature sensor and compatibles. It does not include
 * the configuration possibilities, where it needs to be set to 'programming mode'
 * during power-up.
 *
 *
 * Copyright (C) 2023 SYS TEC electronic AG
 * Author: Andre Werner <andre.werner@systec-electronic.com>
 */

#include <linux/bitfield.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/slab.h>
#include <linux/types.h>

/* Measurement times */
#define HS3001_WAKEUP_TIME      100     /* us */
#define HS3001_8BIT_RESOLUTION  550     /* us */
#define HS3001_10BIT_RESOLUTION 1310    /* us */
#define HS3001_12BIT_RESOLUTION 4500    /* us */
#define HS3001_14BIT_RESOLUTION 16900   /* us */

#define HS3001_RESPONSE_LENGTH  4

#define HS3001_FIXPOINT_ARITH   1000U

#define HS3001_MASK_HUMIDITY_0X3FFF     GENMASK(13, 0)
#define HS3001_MASK_STATUS_0XC0 GENMASK(7, 6)

/* Definitions for Status Bits of A/D Data */
#define HS3001_DATA_VALID       0x00    /* Valid Data */
#define HS3001_DATA_STALE       0x01    /* Stale Data */

struct hs3001_data {
        struct i2c_client *client;
        u32 wait_time;          /* in us */
        int temperature;        /* in milli degree */
        u32 humidity;           /* in milli % */
};

static int hs3001_extract_temperature(u16 raw)
{
        /* fixpoint arithmetic 1 digit */
        u32 temp = (raw >> 2) * HS3001_FIXPOINT_ARITH * 165;

        temp /= (1 << 14) - 1;

        return (int)temp - 40 * HS3001_FIXPOINT_ARITH;
}

static u32 hs3001_extract_humidity(u16 raw)
{
        u32 hum = (raw & HS3001_MASK_HUMIDITY_0X3FFF) * HS3001_FIXPOINT_ARITH * 100;

        return hum / (1 << 14) - 1;
}

static int hs3001_data_fetch_command(struct i2c_client *client,
                                     struct hs3001_data *data)
{
        int ret;
        u8 buf[HS3001_RESPONSE_LENGTH];
        u8 hs3001_status;

        ret = i2c_master_recv(client, buf, HS3001_RESPONSE_LENGTH);
        if (ret != HS3001_RESPONSE_LENGTH) {
                ret = ret < 0 ? ret : -EIO;
                dev_dbg(&client->dev,
                        "Error in i2c communication. Error code: %d.\n", ret);
                return ret;
        }

        hs3001_status = FIELD_GET(HS3001_MASK_STATUS_0XC0, buf[0]);
        if (hs3001_status == HS3001_DATA_STALE) {
                dev_dbg(&client->dev, "Sensor busy.\n");
                return -EBUSY;
        }
        if (hs3001_status != HS3001_DATA_VALID) {
                dev_dbg(&client->dev, "Data invalid.\n");
                return -EIO;
        }

        data->humidity =
                hs3001_extract_humidity(be16_to_cpup((__be16 *)&buf[0]));
        data->temperature =
                hs3001_extract_temperature(be16_to_cpup((__be16 *)&buf[2]));

        return 0;
}

static umode_t hs3001_is_visible(const void *data, enum hwmon_sensor_types type,
                                 u32 attr, int channel)
{
        /* Both, humidity and temperature can only be read. */
        return 0444;
}

static int hs3001_read(struct device *dev, enum hwmon_sensor_types type,
                       u32 attr, int channel, long *val)
{
        struct hs3001_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        int ret;

        ret = i2c_master_send(client, NULL, 0);
        if (ret < 0)
                return ret;

        /*
         * Sensor needs some time to process measurement depending on
         * resolution (ref. datasheet)
         */
        fsleep(data->wait_time);

        ret = hs3001_data_fetch_command(client, data);
        if (ret < 0)
                return ret;

        switch (type) {
        case hwmon_temp:
                switch (attr) {
                case hwmon_temp_input:
                        *val = data->temperature;
                        break;
                default:
                        return -EINVAL;
                }
                break;
        case hwmon_humidity:
                switch (attr) {
                case hwmon_humidity_input:
                        *val = data->humidity;
                        break;
                default:
                        return -EINVAL;
                }
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static const struct hwmon_channel_info *hs3001_info[] = {
        HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
        HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
        NULL
};

static const struct hwmon_ops hs3001_hwmon_ops = {
        .is_visible = hs3001_is_visible,
        .read = hs3001_read,
};

static const struct hwmon_chip_info hs3001_chip_info = {
        .ops = &hs3001_hwmon_ops,
        .info = hs3001_info,
};

/* device ID table */
static const struct i2c_device_id hs3001_ids[] = {
        { "hs3001" },
        { },
};

MODULE_DEVICE_TABLE(i2c, hs3001_ids);

static const struct of_device_id hs3001_of_match[] = {
        {.compatible = "renesas,hs3001"},
        { },
};

MODULE_DEVICE_TABLE(of, hs3001_of_match);

static int hs3001_probe(struct i2c_client *client)
{
        struct hs3001_data *data;
        struct device *hwmon_dev;
        struct device *dev = &client->dev;

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

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

        data->client = client;

        /*
         * Measurement time = wake-up time + measurement time temperature
         * + measurement time humidity. This is currently static, because
         * enabling programming mode is not supported, yet.
         */
        data->wait_time = (HS3001_WAKEUP_TIME + HS3001_14BIT_RESOLUTION +
                           HS3001_14BIT_RESOLUTION);

        hwmon_dev = devm_hwmon_device_register_with_info(dev,
                                                         client->name,
                                                         data,
                                                         &hs3001_chip_info,
                                                         NULL);

        if (IS_ERR(hwmon_dev))
                return dev_err_probe(dev, PTR_ERR(hwmon_dev),
                                     "Unable to register hwmon device.\n");

        return 0;
}

static struct i2c_driver hs3001_i2c_driver = {
        .driver = {
                   .name = "hs3001",
                   .of_match_table = hs3001_of_match,
        },
        .probe = hs3001_probe,
        .id_table = hs3001_ids,
};

module_i2c_driver(hs3001_i2c_driver);

MODULE_AUTHOR("Andre Werner <andre.werner@systec-electronic.com>");
MODULE_DESCRIPTION("HS3001 humidity and temperature sensor base driver");
MODULE_LICENSE("GPL");