// SPDX-License-Identifier: GPL-2.0-only
/*
 * MAX1241 low-power, 12-bit serial ADC
 *
 * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
 */

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

#define MAX1241_VAL_MASK GENMASK(11, 0)
#define MAX1241_SHUTDOWN_DELAY_USEC 4

enum max1241_id {
        max1241,
};

struct max1241 {
        struct spi_device *spi;
        struct mutex lock;
        struct regulator *vref;
        struct gpio_desc *shutdown;

        __be16 data __aligned(IIO_DMA_MINALIGN);
};

static const struct iio_chan_spec max1241_channels[] = {
        {
                .type = IIO_VOLTAGE,
                .indexed = 1,
                .channel = 0,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                                BIT(IIO_CHAN_INFO_SCALE),
        },
};

static int max1241_read(struct max1241 *adc)
{
        struct spi_transfer xfers[] = {
                /*
                 * Begin conversion by bringing /CS low for at least
                 * tconv us.
                 */
                {
                        .len = 0,
                        .delay.value = 8,
                        .delay.unit = SPI_DELAY_UNIT_USECS,
                },
                /*
                 * Then read two bytes of data in our RX buffer.
                 */
                {
                        .rx_buf = &adc->data,
                        .len = 2,
                },
        };

        return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
}

static int max1241_read_raw(struct iio_dev *indio_dev,
                        struct iio_chan_spec const *chan,
                        int *val, int *val2, long mask)
{
        int ret, vref_uV;
        struct max1241 *adc = iio_priv(indio_dev);

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                mutex_lock(&adc->lock);

                if (adc->shutdown) {
                        gpiod_set_value(adc->shutdown, 0);
                        udelay(MAX1241_SHUTDOWN_DELAY_USEC);
                        ret = max1241_read(adc);
                        gpiod_set_value(adc->shutdown, 1);
                } else
                        ret = max1241_read(adc);

                if (ret) {
                        mutex_unlock(&adc->lock);
                        return ret;
                }

                *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;

                mutex_unlock(&adc->lock);
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                vref_uV = regulator_get_voltage(adc->vref);

                if (vref_uV < 0)
                        return vref_uV;

                *val = vref_uV / 1000;
                *val2 = 12;

                return IIO_VAL_FRACTIONAL_LOG2;
        default:
                return -EINVAL;
        }
}

static const struct iio_info max1241_info = {
        .read_raw = max1241_read_raw,
};

static void max1241_disable_vref_action(void *data)
{
        struct max1241 *adc = data;
        struct device *dev = &adc->spi->dev;
        int err;

        err = regulator_disable(adc->vref);
        if (err)
                dev_err(dev, "could not disable vref regulator.\n");
}

static int max1241_probe(struct spi_device *spi)
{
        struct device *dev = &spi->dev;
        struct iio_dev *indio_dev;
        struct max1241 *adc;
        int ret;

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

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

        ret = devm_regulator_get_enable(dev, "vdd");
        if (ret)
                return dev_err_probe(dev, ret,
                                     "failed to get/enable vdd regulator\n");

        adc->vref = devm_regulator_get(dev, "vref");
        if (IS_ERR(adc->vref))
                return dev_err_probe(dev, PTR_ERR(adc->vref),
                                     "failed to get vref regulator\n");

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

        ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);
        if (ret) {
                dev_err(dev, "could not set up vref regulator cleanup action\n");
                return ret;
        }

        adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",
                                                GPIOD_OUT_HIGH);
        if (IS_ERR(adc->shutdown))
                return dev_err_probe(dev, PTR_ERR(adc->shutdown),
                                     "cannot get shutdown gpio\n");

        if (adc->shutdown)
                dev_dbg(dev, "shutdown pin passed, low-power mode enabled");
        else
                dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");

        indio_dev->name = spi_get_device_id(spi)->name;
        indio_dev->info = &max1241_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = max1241_channels;
        indio_dev->num_channels = ARRAY_SIZE(max1241_channels);

        return devm_iio_device_register(dev, indio_dev);
}

static const struct spi_device_id max1241_id[] = {
        { "max1241", max1241 },
        { }
};

static const struct of_device_id max1241_dt_ids[] = {
        { .compatible = "maxim,max1241" },
        { }
};
MODULE_DEVICE_TABLE(of, max1241_dt_ids);

static struct spi_driver max1241_spi_driver = {
        .driver = {
                .name = "max1241",
                .of_match_table = max1241_dt_ids,
        },
        .probe = max1241_probe,
        .id_table = max1241_id,
};
module_spi_driver(max1241_spi_driver);

MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");
MODULE_DESCRIPTION("MAX1241 ADC driver");
MODULE_LICENSE("GPL v2");