// SPDX-License-Identifier: GPL-2.0-only
/*
 * max5487.c - Support for MAX5487, MAX5488, MAX5489 digital potentiometers
 *
 * Copyright (C) 2016 Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>
 */
#include <linux/module.h>
#include <linux/spi/spi.h>

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

#define MAX5487_WRITE_WIPER_A   (0x01 << 8)
#define MAX5487_WRITE_WIPER_B   (0x02 << 8)

/* copy both wiper regs to NV regs */
#define MAX5487_COPY_AB_TO_NV   (0x23 << 8)
/* copy both NV regs to wiper regs */
#define MAX5487_COPY_NV_TO_AB   (0x33 << 8)

#define MAX5487_MAX_POS         255

struct max5487_data {
        struct spi_device *spi;
        int kohms;
};

#define MAX5487_CHANNEL(ch, addr) {                             \
        .type = IIO_RESISTANCE,                                 \
        .indexed = 1,                                           \
        .output = 1,                                            \
        .channel = ch,                                          \
        .address = addr,                                        \
        .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
        .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \
}

static const struct iio_chan_spec max5487_channels[] = {
        MAX5487_CHANNEL(0, MAX5487_WRITE_WIPER_A),
        MAX5487_CHANNEL(1, MAX5487_WRITE_WIPER_B),
};

static int max5487_write_cmd(struct spi_device *spi, u16 cmd)
{
        return spi_write(spi, (const void *) &cmd, sizeof(u16));
}

static int max5487_read_raw(struct iio_dev *indio_dev,
                            struct iio_chan_spec const *chan,
                            int *val, int *val2, long mask)
{
        struct max5487_data *data = iio_priv(indio_dev);

        if (mask != IIO_CHAN_INFO_SCALE)
                return -EINVAL;

        *val = 1000 * data->kohms;
        *val2 = MAX5487_MAX_POS;

        return IIO_VAL_FRACTIONAL;
}

static int max5487_write_raw(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan,
                             int val, int val2, long mask)
{
        struct max5487_data *data = iio_priv(indio_dev);

        if (mask != IIO_CHAN_INFO_RAW)
                return -EINVAL;

        if (val < 0 || val > MAX5487_MAX_POS)
                return -EINVAL;

        return max5487_write_cmd(data->spi, chan->address | val);
}

static const struct iio_info max5487_info = {
        .read_raw = max5487_read_raw,
        .write_raw = max5487_write_raw,
};

static int max5487_spi_probe(struct spi_device *spi)
{
        struct iio_dev *indio_dev;
        struct max5487_data *data;
        const struct spi_device_id *id = spi_get_device_id(spi);
        int ret;

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

        spi_set_drvdata(spi, indio_dev);
        data = iio_priv(indio_dev);

        data->spi = spi;
        data->kohms = id->driver_data;

        indio_dev->info = &max5487_info;
        indio_dev->name = id->name;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = max5487_channels;
        indio_dev->num_channels = ARRAY_SIZE(max5487_channels);

        /* restore both wiper regs from NV regs */
        ret = max5487_write_cmd(data->spi, MAX5487_COPY_NV_TO_AB);
        if (ret < 0)
                return ret;

        return iio_device_register(indio_dev);
}

static void max5487_spi_remove(struct spi_device *spi)
{
        struct iio_dev *indio_dev = spi_get_drvdata(spi);
        int ret;

        iio_device_unregister(indio_dev);

        /* save both wiper regs to NV regs */
        ret = max5487_write_cmd(spi, MAX5487_COPY_AB_TO_NV);
        if (ret)
                dev_warn(&spi->dev, "Failed to save wiper regs to NV regs\n");
}

static const struct spi_device_id max5487_id[] = {
        { "MAX5487", 10 },
        { "MAX5488", 50 },
        { "MAX5489", 100 },
        { }
};
MODULE_DEVICE_TABLE(spi, max5487_id);

static const struct acpi_device_id max5487_acpi_match[] = {
        { "MAX5487", 10 },
        { "MAX5488", 50 },
        { "MAX5489", 100 },
        { }
};
MODULE_DEVICE_TABLE(acpi, max5487_acpi_match);

static struct spi_driver max5487_driver = {
        .driver = {
                .name = "max5487",
                .acpi_match_table = max5487_acpi_match,
        },
        .id_table = max5487_id,
        .probe = max5487_spi_probe,
        .remove = max5487_spi_remove
};
module_spi_driver(max5487_driver);

MODULE_AUTHOR("Cristina-Gabriela Moraru <cristina.moraru09@gmail.com>");
MODULE_DESCRIPTION("max5487 SPI driver");
MODULE_LICENSE("GPL v2");