// SPDX-License-Identifier: GPL-2.0-only
/*
 * Vishay VEML6075 UVA and UVB light sensor
 *
 * Copyright 2023 Javier Carrasco <javier.carrasco.cruz@gmail.com>
 *
 * 7-bit I2C slave, address 0x10
 */

#include <linux/bitfield.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/regmap.h>
#include <linux/units.h>

#include <linux/iio/iio.h>

#define VEML6075_CMD_CONF       0x00 /* configuration register */
#define VEML6075_CMD_UVA        0x07 /* UVA channel */
#define VEML6075_CMD_UVB        0x09 /* UVB channel */
#define VEML6075_CMD_COMP1      0x0A /* visible light compensation */
#define VEML6075_CMD_COMP2      0x0B /* infrarred light compensation */
#define VEML6075_CMD_ID         0x0C /* device ID */

#define VEML6075_CONF_IT        GENMASK(6, 4) /* intregration time */
#define VEML6075_CONF_HD        BIT(3) /* dynamic setting */
#define VEML6075_CONF_TRIG      BIT(2) /* trigger */
#define VEML6075_CONF_AF        BIT(1) /* active force enable */
#define VEML6075_CONF_SD        BIT(0) /* shutdown */

#define VEML6075_IT_50_MS       0x00
#define VEML6075_IT_100_MS      0x01
#define VEML6075_IT_200_MS      0x02
#define VEML6075_IT_400_MS      0x03
#define VEML6075_IT_800_MS      0x04

#define VEML6075_AF_DISABLE     0x00
#define VEML6075_AF_ENABLE      0x01

#define VEML6075_SD_DISABLE     0x00
#define VEML6075_SD_ENABLE      0x01

/* Open-air coefficients and responsivity */
#define VEML6075_A_COEF         2220
#define VEML6075_B_COEF         1330
#define VEML6075_C_COEF         2950
#define VEML6075_D_COEF         1740
#define VEML6075_UVA_RESP       1461
#define VEML6075_UVB_RESP       2591

static const int veml6075_it_ms[] = { 50, 100, 200, 400, 800 };

struct veml6075_data {
        struct i2c_client *client;
        struct regmap *regmap;
        /*
         * prevent integration time modification and triggering
         * measurements while a measurement is underway.
         */
        struct mutex lock;
};

/* channel number */
enum veml6075_chan {
        CH_UVA,
        CH_UVB,
};

static const struct iio_chan_spec veml6075_channels[] = {
        {
                .type = IIO_INTENSITY,
                .channel = CH_UVA,
                .modified = 1,
                .channel2 = IIO_MOD_LIGHT_UVA,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                        BIT(IIO_CHAN_INFO_SCALE),
                .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
                .info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME),
        },
        {
                .type = IIO_INTENSITY,
                .channel = CH_UVB,
                .modified = 1,
                .channel2 = IIO_MOD_LIGHT_UVB,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                        BIT(IIO_CHAN_INFO_SCALE),
                .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
                .info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME),
        },
        {
                .type = IIO_UVINDEX,
                .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
                .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
                .info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME),
        },
};

static int veml6075_request_measurement(struct veml6075_data *data)
{
        int ret, conf, int_time;

        ret = regmap_read(data->regmap, VEML6075_CMD_CONF, &conf);
        if (ret < 0)
                return ret;

        /* disable shutdown and trigger measurement */
        ret = regmap_write(data->regmap, VEML6075_CMD_CONF,
                           (conf | VEML6075_CONF_TRIG) & ~VEML6075_CONF_SD);
        if (ret < 0)
                return ret;

        /*
         * A measurement requires between 1.30 and 1.40 times the integration
         * time for all possible configurations. Using a 1.50 factor simplifies
         * operations and ensures reliability under all circumstances.
         */
        int_time = veml6075_it_ms[FIELD_GET(VEML6075_CONF_IT, conf)];
        msleep(int_time + (int_time / 2));

        /* shutdown again, data registers are still accessible */
        return regmap_update_bits(data->regmap, VEML6075_CMD_CONF,
                                  VEML6075_CONF_SD, VEML6075_CONF_SD);
}

static int veml6075_uva_comp(int raw_uva, int comp1, int comp2)
{
        int comp1a_c, comp2a_c, uva_comp;

        comp1a_c = (comp1 * VEML6075_A_COEF) / 1000U;
        comp2a_c = (comp2 * VEML6075_B_COEF) / 1000U;
        uva_comp = raw_uva - comp1a_c - comp2a_c;

        return clamp_val(uva_comp, 0, U16_MAX);
}

static int veml6075_uvb_comp(int raw_uvb, int comp1, int comp2)
{
        int comp1b_c, comp2b_c, uvb_comp;

        comp1b_c = (comp1 * VEML6075_C_COEF) / 1000U;
        comp2b_c = (comp2 * VEML6075_D_COEF) / 1000U;
        uvb_comp = raw_uvb - comp1b_c - comp2b_c;

        return clamp_val(uvb_comp, 0, U16_MAX);
}

static int veml6075_read_comp(struct veml6075_data *data, int *c1, int *c2)
{
        int ret;

        ret = regmap_read(data->regmap, VEML6075_CMD_COMP1, c1);
        if (ret < 0)
                return ret;

        return regmap_read(data->regmap, VEML6075_CMD_COMP2, c2);
}

static int veml6075_read_uv_direct(struct veml6075_data *data, int chan,
                                   int *val)
{
        int c1, c2, ret;

        guard(mutex)(&data->lock);

        ret = veml6075_request_measurement(data);
        if (ret < 0)
                return ret;

        ret = veml6075_read_comp(data, &c1, &c2);
        if (ret < 0)
                return ret;

        switch (chan) {
        case CH_UVA:
                ret = regmap_read(data->regmap, VEML6075_CMD_UVA, val);
                if (ret < 0)
                        return ret;

                *val = veml6075_uva_comp(*val, c1, c2);
                return IIO_VAL_INT;
        case CH_UVB:
                ret = regmap_read(data->regmap, VEML6075_CMD_UVB, val);
                if (ret < 0)
                        return ret;

                *val = veml6075_uvb_comp(*val, c1, c2);
                return IIO_VAL_INT;
        default:
                return -EINVAL;
        }
}

static int veml6075_read_int_time_index(struct veml6075_data *data)
{
        int ret, conf, int_index;

        ret = regmap_read(data->regmap, VEML6075_CMD_CONF, &conf);
        if (ret < 0)
                return ret;

        int_index = FIELD_GET(VEML6075_CONF_IT, conf);
        if (int_index >= ARRAY_SIZE(veml6075_it_ms))
                return -EINVAL;

        return int_index;
}

static int veml6075_read_int_time_ms(struct veml6075_data *data, int *val)
{
        int int_index;

        guard(mutex)(&data->lock);
        int_index = veml6075_read_int_time_index(data);
        if (int_index < 0)
                return int_index;

        *val = veml6075_it_ms[int_index];

        return IIO_VAL_INT;
}

static int veml6075_get_uvi_micro(struct veml6075_data *data, int uva_comp,
                                  int uvb_comp)
{
        int uvia_micro = uva_comp * VEML6075_UVA_RESP;
        int uvib_micro = uvb_comp * VEML6075_UVB_RESP;
        int int_index;

        int_index = veml6075_read_int_time_index(data);
        if (int_index < 0)
                return int_index;

        switch (int_index) {
        case VEML6075_IT_50_MS:
                return uvia_micro + uvib_micro;
        case VEML6075_IT_100_MS:
        case VEML6075_IT_200_MS:
        case VEML6075_IT_400_MS:
        case VEML6075_IT_800_MS:
                return (uvia_micro + uvib_micro) / (2 << int_index);
        default:
                return -EINVAL;
        }
}

static int veml6075_read_uvi(struct veml6075_data *data, int *val, int *val2)
{
        int ret, c1, c2, uva, uvb, uvi_micro;

        guard(mutex)(&data->lock);

        ret = veml6075_request_measurement(data);
        if (ret < 0)
                return ret;

        ret = veml6075_read_comp(data, &c1, &c2);
        if (ret < 0)
                return ret;

        ret = regmap_read(data->regmap, VEML6075_CMD_UVA, &uva);
        if (ret < 0)
                return ret;

        ret = regmap_read(data->regmap, VEML6075_CMD_UVB, &uvb);
        if (ret < 0)
                return ret;

        uvi_micro = veml6075_get_uvi_micro(data, veml6075_uva_comp(uva, c1, c2),
                                           veml6075_uvb_comp(uvb, c1, c2));
        if (uvi_micro < 0)
                return uvi_micro;

        *val = uvi_micro / MICRO;
        *val2 = uvi_micro % MICRO;

        return IIO_VAL_INT_PLUS_MICRO;
}

static int veml6075_read_responsivity(int chan, int *val, int *val2)
{
        /* scale = 1 / resp */
        switch (chan) {
        case CH_UVA:
                /* resp = 0.93 c/uW/cm2: scale = 1.75268817 */
                *val = 1;
                *val2 = 75268817;
                return IIO_VAL_INT_PLUS_NANO;
        case CH_UVB:
                /* resp = 2.1 c/uW/cm2: scale = 0.476190476 */
                *val = 0;
                *val2 = 476190476;
                return IIO_VAL_INT_PLUS_NANO;
        default:
                return -EINVAL;
        }
}

static int veml6075_read_avail(struct iio_dev *indio_dev,
                               struct iio_chan_spec const *chan,
                               const int **vals, int *type, int *length,
                               long mask)
{
        switch (mask) {
        case IIO_CHAN_INFO_INT_TIME:
                *length = ARRAY_SIZE(veml6075_it_ms);
                *vals = veml6075_it_ms;
                *type = IIO_VAL_INT;
                return IIO_AVAIL_LIST;

        default:
                return -EINVAL;
        }
}

static int veml6075_read_raw(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan,
                             int *val, int *val2, long mask)
{
        struct veml6075_data *data = iio_priv(indio_dev);

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                return veml6075_read_uv_direct(data, chan->channel, val);
        case IIO_CHAN_INFO_PROCESSED:
                return veml6075_read_uvi(data, val, val2);
        case IIO_CHAN_INFO_INT_TIME:
                return veml6075_read_int_time_ms(data, val);
        case IIO_CHAN_INFO_SCALE:
                return veml6075_read_responsivity(chan->channel, val, val2);
        default:
                return -EINVAL;
        }
}

static int veml6075_write_int_time_ms(struct veml6075_data *data, int val)
{
        int i = ARRAY_SIZE(veml6075_it_ms);

        guard(mutex)(&data->lock);

        while (i-- > 0) {
                if (val == veml6075_it_ms[i])
                        break;
        }
        if (i < 0)
                return -EINVAL;

        return regmap_update_bits(data->regmap, VEML6075_CMD_CONF,
                                  VEML6075_CONF_IT,
                                  FIELD_PREP(VEML6075_CONF_IT, i));
}

static int veml6075_write_raw(struct iio_dev *indio_dev,
                              struct iio_chan_spec const *chan,
                              int val, int val2, long mask)
{
        struct veml6075_data *data = iio_priv(indio_dev);

        switch (mask) {
        case IIO_CHAN_INFO_INT_TIME:
                return veml6075_write_int_time_ms(data, val);
        default:
                return -EINVAL;
        }
}

static const struct iio_info veml6075_info = {
        .read_avail = veml6075_read_avail,
        .read_raw = veml6075_read_raw,
        .write_raw = veml6075_write_raw,
};

static bool veml6075_readable_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case VEML6075_CMD_CONF:
        case VEML6075_CMD_UVA:
        case VEML6075_CMD_UVB:
        case VEML6075_CMD_COMP1:
        case VEML6075_CMD_COMP2:
        case VEML6075_CMD_ID:
                return true;
        default:
                return false;
        }
}

static bool veml6075_writable_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case VEML6075_CMD_CONF:
                return true;
        default:
                return false;
        }
}

static const struct regmap_config veml6075_regmap_config = {
        .name = "veml6075",
        .reg_bits = 8,
        .val_bits = 16,
        .max_register = VEML6075_CMD_ID,
        .readable_reg = veml6075_readable_reg,
        .writeable_reg = veml6075_writable_reg,
        .val_format_endian = REGMAP_ENDIAN_LITTLE,
};

static int veml6075_probe(struct i2c_client *client)
{
        struct veml6075_data *data;
        struct iio_dev *indio_dev;
        struct regmap *regmap;
        int config, ret;

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

        regmap = devm_regmap_init_i2c(client, &veml6075_regmap_config);
        if (IS_ERR(regmap))
                return PTR_ERR(regmap);

        data = iio_priv(indio_dev);
        data->client = client;
        data->regmap = regmap;

        mutex_init(&data->lock);

        indio_dev->name = "veml6075";
        indio_dev->info = &veml6075_info;
        indio_dev->channels = veml6075_channels;
        indio_dev->num_channels = ARRAY_SIZE(veml6075_channels);
        indio_dev->modes = INDIO_DIRECT_MODE;

        ret = devm_regulator_get_enable(&client->dev, "vdd");
        if (ret < 0)
                return ret;

        /* default: 100ms integration time, active force enable, shutdown */
        config = FIELD_PREP(VEML6075_CONF_IT, VEML6075_IT_100_MS) |
                FIELD_PREP(VEML6075_CONF_AF, VEML6075_AF_ENABLE) |
                FIELD_PREP(VEML6075_CONF_SD, VEML6075_SD_ENABLE);
        ret = regmap_write(data->regmap, VEML6075_CMD_CONF, config);
        if (ret < 0)
                return ret;

        return devm_iio_device_register(&client->dev, indio_dev);
}

static const struct i2c_device_id veml6075_id[] = {
        { "veml6075" },
        { }
};
MODULE_DEVICE_TABLE(i2c, veml6075_id);

static const struct of_device_id veml6075_of_match[] = {
        { .compatible = "vishay,veml6075" },
        { }
};
MODULE_DEVICE_TABLE(of, veml6075_of_match);

static struct i2c_driver veml6075_driver = {
        .driver = {
                .name   = "veml6075",
                .of_match_table = veml6075_of_match,
        },
        .probe = veml6075_probe,
        .id_table = veml6075_id,
};

module_i2c_driver(veml6075_driver);

MODULE_AUTHOR("Javier Carrasco <javier.carrasco.cruz@gmail.com>");
MODULE_DESCRIPTION("Vishay VEML6075 UVA and UVB light sensor driver");
MODULE_LICENSE("GPL");