// SPDX-License-Identifier: GPL-2.0
/*
 * Generic sigma delta modulator driver
 *
 * Copyright (C) 2017, STMicroelectronics - All Rights Reserved
 * Author: Arnaud Pouliquen <arnaud.pouliquen@st.com>.
 */

#include <linux/iio/backend.h>
#include <linux/iio/iio.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/regulator/consumer.h>

static const struct iio_info iio_sd_mod_iio_info;

static const struct iio_chan_spec iio_sd_mod_ch = {
        .type = IIO_VOLTAGE,
        .indexed = 1,
        .scan_type = {
                .sign = 'u',
                .realbits = 1,
                .shift = 0,
        },
};

struct iio_sd_backend_priv {
        struct regulator *vref;
        int vref_mv;
};

static int iio_sd_mod_enable(struct iio_backend *backend)
{
        struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);

        if (priv->vref)
                return regulator_enable(priv->vref);

        return 0;
};

static void iio_sd_mod_disable(struct iio_backend *backend)
{
        struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);

        if (priv->vref)
                regulator_disable(priv->vref);
};

static int iio_sd_mod_read(struct iio_backend *backend, struct iio_chan_spec const *chan, int *val,
                           int *val2, long mask)
{
        struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);

        switch (mask) {
        case IIO_CHAN_INFO_SCALE:
                *val = priv->vref_mv;
                return IIO_VAL_INT;

        case IIO_CHAN_INFO_OFFSET:
                *val = 0;
                return IIO_VAL_INT;
        }

        return -EOPNOTSUPP;
};

static const struct iio_backend_ops sd_backend_ops = {
        .enable = iio_sd_mod_enable,
        .disable = iio_sd_mod_disable,
        .read_raw = iio_sd_mod_read,
};

static const struct iio_backend_info sd_backend_info = {
        .name = "sd-modulator",
        .ops = &sd_backend_ops,
};

static int iio_sd_mod_register(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct iio_dev *iio;

        iio = devm_iio_device_alloc(dev, 0);
        if (!iio)
                return -ENOMEM;

        iio->name = dev_name(dev);
        iio->info = &iio_sd_mod_iio_info;
        iio->modes = INDIO_BUFFER_HARDWARE;

        iio->num_channels = 1;
        iio->channels = &iio_sd_mod_ch;

        platform_set_drvdata(pdev, iio);

        return devm_iio_device_register(&pdev->dev, iio);
}

static int iio_sd_mod_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct regulator *vref;
        struct iio_sd_backend_priv *priv;
        int ret;

        /* If sd modulator is not defined as an IIO backend device, fallback to legacy */
        if (!device_property_present(dev, "#io-backend-cells"))
                return iio_sd_mod_register(pdev);

        priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        /*
         * Get regulator reference if any, but don't enable regulator right now.
         * Rely on enable and disable callbacks to manage regulator power.
         */
        vref = devm_regulator_get_optional(dev, "vref");
        if (IS_ERR(vref)) {
                if (PTR_ERR(vref) != -ENODEV)
                        return dev_err_probe(dev, PTR_ERR(vref), "Failed to get vref\n");
        } else {
                /*
                 * Retrieve voltage right now, as regulator_get_voltage() provides it whatever
                 * the state of the regulator.
                 */
                ret = regulator_get_voltage(vref);
                if (ret < 0)
                        return ret;

                priv->vref = vref;
                priv->vref_mv = ret / 1000;
        }

        return devm_iio_backend_register(&pdev->dev, &sd_backend_info, priv);
};

static const struct of_device_id sd_adc_of_match[] = {
        { .compatible = "sd-modulator" },
        { .compatible = "ads1201" },
        { }
};
MODULE_DEVICE_TABLE(of, sd_adc_of_match);

static struct platform_driver iio_sd_mod_adc = {
        .driver = {
                .name = "iio_sd_adc_mod",
                .of_match_table = sd_adc_of_match,
        },
        .probe = iio_sd_mod_probe,
};

module_platform_driver(iio_sd_mod_adc);

MODULE_DESCRIPTION("Basic sigma delta modulator");
MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
MODULE_LICENSE("GPL v2");
MODULE_IMPORT_NS("IIO_BACKEND");