// SPDX-License-Identifier: GPL-2.0
/*
 * iio/adc/max11100.c
 * Maxim max11100 ADC Driver with IIO interface
 *
 * Copyright (C) 2016-17 Renesas Electronics Corporation
 * Copyright (C) 2016-17 Jacopo Mondi
 */
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/regulator/consumer.h>
#include <linux/spi/spi.h>
#include <linux/unaligned.h>

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

/*
 * LSB is the ADC single digital step
 * 1 LSB = (vref_mv / 2 ^ 16)
 *
 * LSB is used to calculate analog voltage value
 * from the number of ADC steps count
 *
 * Ain = (count * LSB)
 */
#define MAX11100_LSB_DIV                (1 << 16)

struct max11100_state {
        struct regulator *vref_reg;
        struct spi_device *spi;

        /*
         * DMA (thus cache coherency maintenance) may require the
         * transfer buffers to live in their own cache lines.
         */
        u8 buffer[3] __aligned(IIO_DMA_MINALIGN);
};

static const struct iio_chan_spec max11100_channels[] = {
        { /* [0] */
                .type = IIO_VOLTAGE,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                                      BIT(IIO_CHAN_INFO_SCALE),
        },
};

static int max11100_read_single(struct iio_dev *indio_dev, int *val)
{
        int ret;
        struct max11100_state *state = iio_priv(indio_dev);

        ret = spi_read(state->spi, state->buffer, sizeof(state->buffer));
        if (ret) {
                dev_err(&indio_dev->dev, "SPI transfer failed\n");
                return ret;
        }

        /* the first 8 bits sent out from ADC must be 0s */
        if (state->buffer[0]) {
                dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n");
                return -EINVAL;
        }

        *val = get_unaligned_be16(&state->buffer[1]);

        return 0;
}

static int max11100_read_raw(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan,
                             int *val, int *val2, long info)
{
        int ret, vref_uv;
        struct max11100_state *state = iio_priv(indio_dev);

        switch (info) {
        case IIO_CHAN_INFO_RAW:
                ret = max11100_read_single(indio_dev, val);
                if (ret)
                        return ret;

                return IIO_VAL_INT;

        case IIO_CHAN_INFO_SCALE:
                vref_uv = regulator_get_voltage(state->vref_reg);
                if (vref_uv < 0)
                        /* dummy regulator "get_voltage" returns -EINVAL */
                        return -EINVAL;

                *val =  vref_uv / 1000;
                *val2 = MAX11100_LSB_DIV;
                return IIO_VAL_FRACTIONAL;
        }

        return -EINVAL;
}

static const struct iio_info max11100_info = {
        .read_raw = max11100_read_raw,
};

static void max11100_regulator_disable(void *reg)
{
        regulator_disable(reg);
}

static int max11100_probe(struct spi_device *spi)
{
        int ret;
        struct iio_dev *indio_dev;
        struct max11100_state *state;

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

        state = iio_priv(indio_dev);
        state->spi = spi;

        indio_dev->name = "max11100";
        indio_dev->info = &max11100_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = max11100_channels;
        indio_dev->num_channels = ARRAY_SIZE(max11100_channels);

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

        ret = regulator_enable(state->vref_reg);
        if (ret)
                return ret;

        ret = devm_add_action_or_reset(&spi->dev, max11100_regulator_disable,
                                       state->vref_reg);
        if (ret)
                return ret;

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

static const struct of_device_id max11100_ids[] = {
        { .compatible = "maxim,max11100" },
        { }
};
MODULE_DEVICE_TABLE(of, max11100_ids);

static struct spi_driver max11100_driver = {
        .driver = {
                .name   = "max11100",
                .of_match_table = max11100_ids,
        },
        .probe          = max11100_probe,
};

module_spi_driver(max11100_driver);

MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
MODULE_DESCRIPTION("Maxim max11100 ADC Driver");
MODULE_LICENSE("GPL v2");