// SPDX-License-Identifier: GPL-2.0+
/*
 * ADS8344 16-bit 8-Channel ADC driver
 *
 * Author: Gregory CLEMENT <gregory.clement@bootlin.com>
 *
 * Datasheet: https://www.ti.com/lit/ds/symlink/ads8344.pdf
 */

#include <linux/delay.h>
#include <linux/iio/buffer.h>
#include <linux/iio/iio.h>
#include <linux/module.h>
#include <linux/regulator/consumer.h>
#include <linux/spi/spi.h>

#define ADS8344_START BIT(7)
#define ADS8344_SINGLE_END BIT(2)
#define ADS8344_CHANNEL(channel) ((channel) << 4)
#define ADS8344_CLOCK_INTERNAL 0x2 /* PD1 = 1 and PD0 = 0 */

struct ads8344 {
        struct spi_device *spi;
        struct regulator *reg;
        /*
         * Lock protecting access to adc->tx_buff and rx_buff,
         * especially from concurrent read on sysfs file.
         */
        struct mutex lock;

        u8 tx_buf __aligned(IIO_DMA_MINALIGN);
        u8 rx_buf[3];
};

#define ADS8344_VOLTAGE_CHANNEL(chan, addr)                             \
        {                                                               \
                .type = IIO_VOLTAGE,                                    \
                .indexed = 1,                                           \
                .channel = chan,                                        \
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \
                .address = addr,                                        \
        }

#define ADS8344_VOLTAGE_CHANNEL_DIFF(chan1, chan2, addr)                \
        {                                                               \
                .type = IIO_VOLTAGE,                                    \
                .indexed = 1,                                           \
                .channel = (chan1),                                     \
                .channel2 = (chan2),                                    \
                .differential = 1,                                      \
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \
                .address = addr,                                        \
        }

static const struct iio_chan_spec ads8344_channels[] = {
        ADS8344_VOLTAGE_CHANNEL(0, 0),
        ADS8344_VOLTAGE_CHANNEL(1, 4),
        ADS8344_VOLTAGE_CHANNEL(2, 1),
        ADS8344_VOLTAGE_CHANNEL(3, 5),
        ADS8344_VOLTAGE_CHANNEL(4, 2),
        ADS8344_VOLTAGE_CHANNEL(5, 6),
        ADS8344_VOLTAGE_CHANNEL(6, 3),
        ADS8344_VOLTAGE_CHANNEL(7, 7),
        ADS8344_VOLTAGE_CHANNEL_DIFF(0, 1, 8),
        ADS8344_VOLTAGE_CHANNEL_DIFF(2, 3, 9),
        ADS8344_VOLTAGE_CHANNEL_DIFF(4, 5, 10),
        ADS8344_VOLTAGE_CHANNEL_DIFF(6, 7, 11),
        ADS8344_VOLTAGE_CHANNEL_DIFF(1, 0, 12),
        ADS8344_VOLTAGE_CHANNEL_DIFF(3, 2, 13),
        ADS8344_VOLTAGE_CHANNEL_DIFF(5, 4, 14),
        ADS8344_VOLTAGE_CHANNEL_DIFF(7, 6, 15),
};

static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
                                  bool differential)
{
        struct spi_device *spi = adc->spi;
        int ret;

        adc->tx_buf = ADS8344_START;
        if (!differential)
                adc->tx_buf |= ADS8344_SINGLE_END;
        adc->tx_buf |= ADS8344_CHANNEL(channel);
        adc->tx_buf |= ADS8344_CLOCK_INTERNAL;

        ret = spi_write(spi, &adc->tx_buf, 1);
        if (ret)
                return ret;

        udelay(9);

        ret = spi_read(spi, adc->rx_buf, sizeof(adc->rx_buf));
        if (ret)
                return ret;

        return adc->rx_buf[0] << 9 | adc->rx_buf[1] << 1 | adc->rx_buf[2] >> 7;
}

static int ads8344_read_raw(struct iio_dev *iio,
                            struct iio_chan_spec const *channel, int *value,
                            int *shift, long mask)
{
        struct ads8344 *adc = iio_priv(iio);

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                mutex_lock(&adc->lock);
                *value = ads8344_adc_conversion(adc, channel->address,
                                                channel->differential);
                mutex_unlock(&adc->lock);
                if (*value < 0)
                        return *value;

                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                *value = regulator_get_voltage(adc->reg);
                if (*value < 0)
                        return *value;

                /* convert regulator output voltage to mV */
                *value /= 1000;
                *shift = 16;

                return IIO_VAL_FRACTIONAL_LOG2;
        default:
                return -EINVAL;
        }
}

static const struct iio_info ads8344_info = {
        .read_raw = ads8344_read_raw,
};

static void ads8344_reg_disable(void *data)
{
        regulator_disable(data);
}

static int ads8344_probe(struct spi_device *spi)
{
        struct iio_dev *indio_dev;
        struct ads8344 *adc;
        int ret;

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

        adc = iio_priv(indio_dev);
        adc->spi = spi;
        mutex_init(&adc->lock);

        indio_dev->name = dev_name(&spi->dev);
        indio_dev->info = &ads8344_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = ads8344_channels;
        indio_dev->num_channels = ARRAY_SIZE(ads8344_channels);

        adc->reg = devm_regulator_get(&spi->dev, "vref");
        if (IS_ERR(adc->reg))
                return PTR_ERR(adc->reg);

        ret = regulator_enable(adc->reg);
        if (ret)
                return ret;

        ret = devm_add_action_or_reset(&spi->dev, ads8344_reg_disable, adc->reg);
        if (ret)
                return ret;

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

static const struct of_device_id ads8344_of_match[] = {
        { .compatible = "ti,ads8344", },
        { }
};
MODULE_DEVICE_TABLE(of, ads8344_of_match);

static struct spi_driver ads8344_driver = {
        .driver = {
                .name = "ads8344",
                .of_match_table = ads8344_of_match,
        },
        .probe = ads8344_probe,
};
module_spi_driver(ads8344_driver);

MODULE_AUTHOR("Gregory CLEMENT <gregory.clement@bootlin.com>");
MODULE_DESCRIPTION("ADS8344 driver");
MODULE_LICENSE("GPL");