// SPDX-License-Identifier: GPL-2.0-only
/*
 * ADS1100 - Texas Instruments Analog-to-Digital Converter
 *
 * Copyright (c) 2023, Topic Embedded Products
 *
 * Datasheet: https://www.ti.com/lit/gpn/ads1100
 * IIO driver for ADS1100 and ADS1000 ADC 16-bit I2C
 */

#include <linux/bitfield.h>
#include <linux/bits.h>
#include <linux/cleanup.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/mutex.h>
#include <linux/property.h>
#include <linux/pm_runtime.h>
#include <linux/regulator/consumer.h>
#include <linux/units.h>

#include <linux/iio/iio.h>
#include <linux/iio/types.h>

/* The ADS1100 has a single byte config register */

/* Conversion in progress bit */
#define ADS1100_CFG_ST_BSY      BIT(7)
/* Single conversion bit */
#define ADS1100_CFG_SC          BIT(4)
/* Data rate */
#define ADS1100_DR_MASK         GENMASK(3, 2)
/* Gain */
#define ADS1100_PGA_MASK        GENMASK(1, 0)

#define ADS1100_CONTINUOUS      0
#define ADS1100_SINGLESHOT      ADS1100_CFG_SC

#define ADS1100_SLEEP_DELAY_MS  2000

static const int ads1100_data_rate[] = { 128, 32, 16, 8 };
static const int ads1100_data_rate_bits[] = { 12, 14, 15, 16 };

struct ads1100_data {
        struct i2c_client *client;
        struct regulator *reg_vdd;
        struct mutex lock;
        int scale_avail[2 * 4]; /* 4 gain settings */
        u8 config;
        bool supports_data_rate; /* Only the ADS1100 can select the rate */
};

static const struct iio_chan_spec ads1100_channel = {
        .type = IIO_VOLTAGE,
        .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
        .info_mask_shared_by_all =
            BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_SAMP_FREQ),
        .info_mask_shared_by_all_available =
            BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_SAMP_FREQ),
        .scan_type = {
                      .sign = 's',
                      .realbits = 16,
                      .storagebits = 16,
                      .endianness = IIO_CPU,
                       },
        .datasheet_name = "AIN",
};

static int ads1100_set_config_bits(struct ads1100_data *data, u8 mask, u8 value)
{
        int ret;
        u8 config = (data->config & ~mask) | (value & mask);

        if (data->config == config)
                return 0;       /* Already done */

        ret = i2c_master_send(data->client, &config, 1);
        if (ret < 0)
                return ret;

        data->config = config;

        return 0;
};

static int ads1100_data_bits(struct ads1100_data *data)
{
        return ads1100_data_rate_bits[FIELD_GET(ADS1100_DR_MASK, data->config)];
}

static int ads1100_get_adc_result(struct ads1100_data *data, int chan, int *val)
{
        int ret;
        __be16 buffer;
        s16 value;

        if (chan != 0)
                return -EINVAL;

        ret = pm_runtime_resume_and_get(&data->client->dev);
        if (ret < 0)
                return ret;

        ret = i2c_master_recv(data->client, (char *)&buffer, sizeof(buffer));

        pm_runtime_put_autosuspend(&data->client->dev);

        if (ret < 0) {
                dev_err(&data->client->dev, "I2C read fail: %d\n", ret);
                return ret;
        }

        /* Value is always 16-bit 2's complement */
        value = be16_to_cpu(buffer);

        /* Shift result to compensate for bit resolution vs. sample rate */
        value <<= 16 - ads1100_data_bits(data);

        *val = sign_extend32(value, 15);

        return 0;
}

static int ads1100_set_scale(struct ads1100_data *data, int val, int val2)
{
        int microvolts;
        int gain;

        /* With Vdd between 2.7 and 5V, the scale is always below 1 */
        if (val)
                return -EINVAL;

        if (!val2)
                return -EINVAL;

        microvolts = regulator_get_voltage(data->reg_vdd);
        /*
         * val2 is in 'micro' units, n = val2 / 1000000
         * result must be millivolts, d = microvolts / 1000
         * the full-scale value is d/n, corresponds to 2^15,
         * hence the gain = (d / n) >> 15, factoring out the 1000 and moving the
         * bitshift so everything fits in 32-bits yields this formula.
         */
        gain = DIV_ROUND_CLOSEST(microvolts, BIT(15)) * MILLI / val2;
        if (gain < BIT(0) || gain > BIT(3))
                return -EINVAL;

        ads1100_set_config_bits(data, ADS1100_PGA_MASK, ffs(gain) - 1);

        return 0;
}

static int ads1100_set_data_rate(struct ads1100_data *data, int chan, int rate)
{
        unsigned int i;
        unsigned int size;

        size = data->supports_data_rate ? ARRAY_SIZE(ads1100_data_rate) : 1;
        for (i = 0; i < size; i++) {
                if (ads1100_data_rate[i] == rate)
                        return ads1100_set_config_bits(data, ADS1100_DR_MASK,
                                                       FIELD_PREP(ADS1100_DR_MASK, i));
        }

        return -EINVAL;
}

static int ads1100_get_vdd_millivolts(struct ads1100_data *data)
{
        return regulator_get_voltage(data->reg_vdd) / (MICRO / MILLI);
}

static void ads1100_calc_scale_avail(struct ads1100_data *data)
{
        int millivolts = ads1100_get_vdd_millivolts(data);
        unsigned int i;

        for (i = 0; i < ARRAY_SIZE(data->scale_avail) / 2; i++) {
                data->scale_avail[i * 2 + 0] = millivolts;
                data->scale_avail[i * 2 + 1] = 15 + i;
        }
}

static int ads1100_read_avail(struct iio_dev *indio_dev,
                              struct iio_chan_spec const *chan,
                              const int **vals, int *type, int *length,
                              long mask)
{
        struct ads1100_data *data = iio_priv(indio_dev);

        if (chan->type != IIO_VOLTAGE)
                return -EINVAL;

        switch (mask) {
        case IIO_CHAN_INFO_SAMP_FREQ:
                *type = IIO_VAL_INT;
                *vals = ads1100_data_rate;
                if (data->supports_data_rate)
                        *length = ARRAY_SIZE(ads1100_data_rate);
                else
                        *length = 1;
                return IIO_AVAIL_LIST;
        case IIO_CHAN_INFO_SCALE:
                *type = IIO_VAL_FRACTIONAL_LOG2;
                *vals = data->scale_avail;
                *length = ARRAY_SIZE(data->scale_avail);
                return IIO_AVAIL_LIST;
        default:
                return -EINVAL;
        }
}

static int ads1100_read_raw(struct iio_dev *indio_dev,
                            struct iio_chan_spec const *chan, int *val,
                            int *val2, long mask)
{
        int ret;
        struct ads1100_data *data = iio_priv(indio_dev);

        guard(mutex)(&data->lock);
        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                if (!iio_device_claim_direct(indio_dev))
                        return -EBUSY;

                ret = ads1100_get_adc_result(data, chan->address, val);
                iio_device_release_direct(indio_dev);
                if (ret < 0)
                        return ret;

                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                /* full-scale is the supply voltage in millivolts */
                *val = ads1100_get_vdd_millivolts(data);
                *val2 = 15 + FIELD_GET(ADS1100_PGA_MASK, data->config);
                return IIO_VAL_FRACTIONAL_LOG2;
        case IIO_CHAN_INFO_SAMP_FREQ:
                *val = ads1100_data_rate[FIELD_GET(ADS1100_DR_MASK,
                                                   data->config)];
                return IIO_VAL_INT;
        default:
                return -EINVAL;
        }
}

static int ads1100_write_raw(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan, int val,
                             int val2, long mask)
{
        struct ads1100_data *data = iio_priv(indio_dev);

        guard(mutex)(&data->lock);
        switch (mask) {
        case IIO_CHAN_INFO_SCALE:
                return ads1100_set_scale(data, val, val2);
        case IIO_CHAN_INFO_SAMP_FREQ:
                return ads1100_set_data_rate(data, chan->address, val);
        default:
                return -EINVAL;
        }
}

static const struct iio_info ads1100_info = {
        .read_avail = ads1100_read_avail,
        .read_raw = ads1100_read_raw,
        .write_raw = ads1100_write_raw,
};

static int ads1100_setup(struct ads1100_data *data)
{
        int ret;
        u8 buffer[3];

        /* Setup continuous sampling mode at 8sps */
        buffer[0] = ADS1100_DR_MASK | ADS1100_CONTINUOUS;
        ret = i2c_master_send(data->client, buffer, 1);
        if (ret < 0)
                return ret;

        ret = i2c_master_recv(data->client, buffer, sizeof(buffer));
        if (ret < 0)
                return ret;

        /* Config register returned in third byte, strip away the busy status */
        data->config = buffer[2] & ~ADS1100_CFG_ST_BSY;

        /* Detect the sample rate capability by checking the DR bits */
        data->supports_data_rate = FIELD_GET(ADS1100_DR_MASK, buffer[2]) != 0;

        return 0;
}

static void ads1100_reg_disable(void *reg)
{
        regulator_disable(reg);
}

static void ads1100_disable_continuous(void *data)
{
        ads1100_set_config_bits(data, ADS1100_CFG_SC, ADS1100_SINGLESHOT);
}

static int ads1100_probe(struct i2c_client *client)
{
        struct iio_dev *indio_dev;
        struct ads1100_data *data;
        struct device *dev = &client->dev;
        int ret;

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

        data = iio_priv(indio_dev);
        dev_set_drvdata(dev, data);
        data->client = client;
        mutex_init(&data->lock);

        indio_dev->name = "ads1100";
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = &ads1100_channel;
        indio_dev->num_channels = 1;
        indio_dev->info = &ads1100_info;

        data->reg_vdd = devm_regulator_get(dev, "vdd");
        if (IS_ERR(data->reg_vdd))
                return dev_err_probe(dev, PTR_ERR(data->reg_vdd),
                                     "Failed to get vdd regulator\n");

        ret = regulator_enable(data->reg_vdd);
        if (ret < 0)
                return dev_err_probe(dev, ret,
                                     "Failed to enable vdd regulator\n");

        ret = devm_add_action_or_reset(dev, ads1100_reg_disable, data->reg_vdd);
        if (ret)
                return ret;

        ret = ads1100_setup(data);
        if (ret)
                return dev_err_probe(dev, ret,
                                     "Failed to communicate with device\n");

        ret = devm_add_action_or_reset(dev, ads1100_disable_continuous, data);
        if (ret)
                return ret;

        ads1100_calc_scale_avail(data);

        pm_runtime_set_autosuspend_delay(dev, ADS1100_SLEEP_DELAY_MS);
        pm_runtime_use_autosuspend(dev);
        pm_runtime_set_active(dev);
        ret = devm_pm_runtime_enable(dev);
        if (ret)
                return dev_err_probe(dev, ret, "Failed to enable pm_runtime\n");

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

        return 0;
}

static int ads1100_runtime_suspend(struct device *dev)
{
        struct ads1100_data *data = dev_get_drvdata(dev);

        ads1100_set_config_bits(data, ADS1100_CFG_SC, ADS1100_SINGLESHOT);
        regulator_disable(data->reg_vdd);

        return 0;
}

static int ads1100_runtime_resume(struct device *dev)
{
        struct ads1100_data *data = dev_get_drvdata(dev);
        int ret;

        ret = regulator_enable(data->reg_vdd);
        if (ret) {
                dev_err(&data->client->dev, "Failed to enable Vdd\n");
                return ret;
        }

        /*
         * We'll always change the mode bit in the config register, so there is
         * no need here to "force" a write to the config register. If the device
         * has been power-cycled, we'll re-write its config register now.
         */
        return ads1100_set_config_bits(data, ADS1100_CFG_SC,
                                       ADS1100_CONTINUOUS);
}

static DEFINE_RUNTIME_DEV_PM_OPS(ads1100_pm_ops,
                                 ads1100_runtime_suspend,
                                 ads1100_runtime_resume,
                                 NULL);

static const struct i2c_device_id ads1100_id[] = {
        { "ads1100" },
        { "ads1000" },
        { }
};

MODULE_DEVICE_TABLE(i2c, ads1100_id);

static const struct of_device_id ads1100_of_match[] = {
        {.compatible = "ti,ads1100" },
        {.compatible = "ti,ads1000" },
        { }
};

MODULE_DEVICE_TABLE(of, ads1100_of_match);

static struct i2c_driver ads1100_driver = {
        .driver = {
                   .name = "ads1100",
                   .of_match_table = ads1100_of_match,
                   .pm = pm_ptr(&ads1100_pm_ops),
        },
        .probe = ads1100_probe,
        .id_table = ads1100_id,
};

module_i2c_driver(ads1100_driver);

MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
MODULE_DESCRIPTION("Texas Instruments ADS1100 ADC driver");
MODULE_LICENSE("GPL");