// SPDX-License-Identifier: GPL-2.0
/*
 * DAC7612 Dual, 12-Bit Serial input Digital-to-Analog Converter
 *
 * Copyright 2019 Qtechnology A/S
 * 2019 Ricardo Ribalda <ribalda@kernel.org>
 *
 * Licensed under the GPL-2.
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/spi/spi.h>
#include <linux/gpio/consumer.h>
#include <linux/iio/iio.h>

#define DAC7612_RESOLUTION 12
#define DAC7612_ADDRESS 4
#define DAC7612_START 5

struct dac7612 {
        struct spi_device *spi;
        struct gpio_desc *loaddacs;
        uint16_t cache[2];

        /*
         * Lock to protect the state of the device from potential concurrent
         * write accesses from userspace. The write operation requires an
         * SPI write, then toggling of a GPIO, so the lock aims to protect
         * the sanity of the entire sequence of operation.
         */
        struct mutex lock;

        /*
         * DMA (thus cache coherency maintenance) requires the
         * transfer buffers to live in their own cache lines.
         */
        uint8_t data[2] ____cacheline_aligned;
};

static int dac7612_cmd_single(struct dac7612 *priv, int channel, u16 val)
{
        int ret;

        priv->data[0] = BIT(DAC7612_START) | (channel << DAC7612_ADDRESS);
        priv->data[0] |= val >> 8;
        priv->data[1] = val & 0xff;

        priv->cache[channel] = val;

        ret = spi_write(priv->spi, priv->data, sizeof(priv->data));
        if (ret)
                return ret;

        gpiod_set_value(priv->loaddacs, 1);
        gpiod_set_value(priv->loaddacs, 0);

        return 0;
}

#define dac7612_CHANNEL(chan, name) {                           \
        .type = IIO_VOLTAGE,                                    \
        .channel = (chan),                                      \
        .indexed = 1,                                           \
        .output = 1,                                            \
        .datasheet_name = name,                                 \
        .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
        .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \
}

static const struct iio_chan_spec dac7612_channels[] = {
        dac7612_CHANNEL(0, "OUTA"),
        dac7612_CHANNEL(1, "OUTB"),
};

static int dac7612_read_raw(struct iio_dev *iio_dev,
                            const struct iio_chan_spec *chan,
                            int *val, int *val2, long mask)
{
        struct dac7612 *priv;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                priv = iio_priv(iio_dev);
                *val = priv->cache[chan->channel];
                return IIO_VAL_INT;

        case IIO_CHAN_INFO_SCALE:
                *val = 1;
                return IIO_VAL_INT;

        default:
                return -EINVAL;
        }
}

static int dac7612_write_raw(struct iio_dev *iio_dev,
                             const struct iio_chan_spec *chan,
                             int val, int val2, long mask)
{
        struct dac7612 *priv = iio_priv(iio_dev);
        int ret;

        if (mask != IIO_CHAN_INFO_RAW)
                return -EINVAL;

        if ((val >= BIT(DAC7612_RESOLUTION)) || val < 0 || val2)
                return -EINVAL;

        if (val == priv->cache[chan->channel])
                return 0;

        mutex_lock(&priv->lock);
        ret = dac7612_cmd_single(priv, chan->channel, val);
        mutex_unlock(&priv->lock);

        return ret;
}

static const struct iio_info dac7612_info = {
        .read_raw = dac7612_read_raw,
        .write_raw = dac7612_write_raw,
};

static int dac7612_probe(struct spi_device *spi)
{
        struct iio_dev *iio_dev;
        struct dac7612 *priv;
        int i;
        int ret;

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

        priv = iio_priv(iio_dev);
        /*
         * LOADDACS pin can be controlled by the driver or externally.
         * When controlled by the driver, the DAC value is updated after
         * every write.
         * When the driver does not control the PIN, the user or an external
         * event can change the value of all DACs by pulsing down the LOADDACs
         * pin.
         */
        priv->loaddacs = devm_gpiod_get_optional(&spi->dev, "ti,loaddacs",
                                                 GPIOD_OUT_LOW);
        if (IS_ERR(priv->loaddacs))
                return PTR_ERR(priv->loaddacs);
        priv->spi = spi;
        spi_set_drvdata(spi, iio_dev);
        iio_dev->info = &dac7612_info;
        iio_dev->modes = INDIO_DIRECT_MODE;
        iio_dev->channels = dac7612_channels;
        iio_dev->num_channels = ARRAY_SIZE(priv->cache);
        iio_dev->name = spi_get_device_id(spi)->name;

        mutex_init(&priv->lock);

        for (i = 0; i < ARRAY_SIZE(priv->cache); i++) {
                ret = dac7612_cmd_single(priv, i, 0);
                if (ret)
                        return ret;
        }

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

static const struct spi_device_id dac7612_id[] = {
        {"ti-dac7612"},
        {}
};
MODULE_DEVICE_TABLE(spi, dac7612_id);

static const struct of_device_id dac7612_of_match[] = {
        { .compatible = "ti,dac7612" },
        { .compatible = "ti,dac7612u" },
        { .compatible = "ti,dac7612ub" },
        { },
};
MODULE_DEVICE_TABLE(of, dac7612_of_match);

static struct spi_driver dac7612_driver = {
        .driver = {
                   .name = "ti-dac7612",
                   .of_match_table = dac7612_of_match,
                   },
        .probe = dac7612_probe,
        .id_table = dac7612_id,
};
module_spi_driver(dac7612_driver);

MODULE_AUTHOR("Ricardo Ribalda <ribalda@kernel.org>");
MODULE_DESCRIPTION("Texas Instruments DAC7612 DAC driver");
MODULE_LICENSE("GPL v2");