// SPDX-License-Identifier: GPL-2.0-only

/*
 * Copyright (c) Rajat Khandelwal <rajat.khandelwal@linux.intel.com>
 *
 * Maxim MAX30208 digital temperature sensor with 0.1°C accuracy
 * (7-bit I2C slave address (0x50 - 0x53))
 */

#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/iio/iio.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/types.h>

#define MAX30208_STATUS                 0x00
#define MAX30208_STATUS_TEMP_RDY        BIT(0)
#define MAX30208_INT_ENABLE             0x01
#define MAX30208_INT_ENABLE_TEMP_RDY    BIT(0)

#define MAX30208_FIFO_OVF_CNTR          0x06
#define MAX30208_FIFO_DATA_CNTR         0x07
#define MAX30208_FIFO_DATA              0x08

#define MAX30208_FIFO_CONFIG            0x0a
#define MAX30208_FIFO_CONFIG_RO         BIT(1)

#define MAX30208_SYSTEM_CTRL            0x0c
#define MAX30208_SYSTEM_CTRL_RESET      0x01

#define MAX30208_TEMP_SENSOR_SETUP      0x14
#define MAX30208_TEMP_SENSOR_SETUP_CONV BIT(0)

struct max30208_data {
        struct i2c_client *client;
        struct mutex lock; /* Lock to prevent concurrent reads of temperature readings */
};

static const struct iio_chan_spec max30208_channels[] = {
        {
                .type = IIO_TEMP,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
        },
};

/**
 * max30208_request() - Request a reading
 * @data: Struct comprising member elements of the device
 *
 * Requests a reading from the device and waits until the conversion is ready.
 */
static int max30208_request(struct max30208_data *data)
{
        /*
         * Sensor can take up to 500 ms to respond so execute a total of
         * 10 retries to give the device sufficient time.
         */
        int retries = 10;
        u8 regval;
        int ret;

        ret = i2c_smbus_read_byte_data(data->client, MAX30208_TEMP_SENSOR_SETUP);
        if (ret < 0)
                return ret;

        regval = ret | MAX30208_TEMP_SENSOR_SETUP_CONV;

        ret = i2c_smbus_write_byte_data(data->client, MAX30208_TEMP_SENSOR_SETUP, regval);
        if (ret)
                return ret;

        while (retries--) {
                ret = i2c_smbus_read_byte_data(data->client, MAX30208_STATUS);
                if (ret < 0)
                        return ret;

                if (ret & MAX30208_STATUS_TEMP_RDY)
                        return 0;

                msleep(50);
        }
        dev_err(&data->client->dev, "Temperature conversion failed\n");

        return -ETIMEDOUT;
}

static int max30208_update_temp(struct max30208_data *data)
{
        u8 data_count;
        int ret;

        mutex_lock(&data->lock);

        ret = max30208_request(data);
        if (ret)
                goto unlock;

        ret = i2c_smbus_read_byte_data(data->client, MAX30208_FIFO_OVF_CNTR);
        if (ret < 0)
                goto unlock;
        else if (!ret) {
                ret = i2c_smbus_read_byte_data(data->client, MAX30208_FIFO_DATA_CNTR);
                if (ret < 0)
                        goto unlock;

                data_count = ret;
        } else
                data_count = 1;

        while (data_count) {
                ret = i2c_smbus_read_word_swapped(data->client, MAX30208_FIFO_DATA);
                if (ret < 0)
                        goto unlock;

                data_count--;
        }

unlock:
        mutex_unlock(&data->lock);
        return ret;
}

/**
 * max30208_config_setup() - Set up FIFO configuration register
 * @data: Struct comprising member elements of the device
 *
 * Sets the rollover bit to '1' to enable overwriting FIFO during overflow.
 */
static int max30208_config_setup(struct max30208_data *data)
{
        u8 regval;
        int ret;

        ret = i2c_smbus_read_byte_data(data->client, MAX30208_FIFO_CONFIG);
        if (ret < 0)
                return ret;

        regval = ret | MAX30208_FIFO_CONFIG_RO;

        ret = i2c_smbus_write_byte_data(data->client, MAX30208_FIFO_CONFIG, regval);
        if (ret)
                return ret;

        return 0;
}

static int max30208_read(struct iio_dev *indio_dev,
                         struct iio_chan_spec const *chan,
                         int *val, int *val2, long mask)
{
        struct max30208_data *data = iio_priv(indio_dev);
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                ret = max30208_update_temp(data);
                if (ret < 0)
                        return ret;

                *val = sign_extend32(ret, 15);
                return IIO_VAL_INT;

        case IIO_CHAN_INFO_SCALE:
                *val = 5;
                return IIO_VAL_INT;

        default:
                return -EINVAL;
        }
}

static const struct iio_info max30208_info = {
        .read_raw = max30208_read,
};

static int max30208_probe(struct i2c_client *i2c)
{
        struct device *dev = &i2c->dev;
        struct max30208_data *data;
        struct iio_dev *indio_dev;
        int ret;

        indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
        if (!indio_dev)
                return -ENOMEM;

        data = iio_priv(indio_dev);
        data->client = i2c;
        mutex_init(&data->lock);

        indio_dev->name = "max30208";
        indio_dev->channels = max30208_channels;
        indio_dev->num_channels = ARRAY_SIZE(max30208_channels);
        indio_dev->info = &max30208_info;
        indio_dev->modes = INDIO_DIRECT_MODE;

        ret = i2c_smbus_write_byte_data(data->client, MAX30208_SYSTEM_CTRL,
                                        MAX30208_SYSTEM_CTRL_RESET);
        if (ret) {
                dev_err(dev, "Failure in performing reset\n");
                return ret;
        }

        msleep(50);

        ret = max30208_config_setup(data);
        if (ret)
                return ret;

        ret = devm_iio_device_register(dev, indio_dev);
        if (ret) {
                dev_err(dev, "Failed to register IIO device\n");
                return ret;
        }

        return 0;
}

static const struct i2c_device_id max30208_id_table[] = {
        { "max30208" },
        { }
};
MODULE_DEVICE_TABLE(i2c, max30208_id_table);

static const struct acpi_device_id max30208_acpi_match[] = {
        { "MAX30208" },
        { }
};
MODULE_DEVICE_TABLE(acpi, max30208_acpi_match);

static const struct of_device_id max30208_of_match[] = {
        { .compatible = "maxim,max30208" },
        { }
};
MODULE_DEVICE_TABLE(of, max30208_of_match);

static struct i2c_driver max30208_driver = {
        .driver = {
                .name = "max30208",
                .of_match_table = max30208_of_match,
                .acpi_match_table = max30208_acpi_match,
        },
        .probe = max30208_probe,
        .id_table = max30208_id_table,
};
module_i2c_driver(max30208_driver);

MODULE_AUTHOR("Rajat Khandelwal <rajat.khandelwal@linux.intel.com>");
MODULE_DESCRIPTION("Maxim MAX30208 digital temperature sensor");
MODULE_LICENSE("GPL");