/**
 * Copyright (C) 2017 Axis Communications AB
 *
 * Driver for Texas Instruments' ADC084S021 ADC chip.
 * Datasheets can be found here:
 * http://www.ti.com/lit/ds/symlink/adc084s021.pdf
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/err.h>
#include <linux/spi/spi.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/iio/iio.h>
#include <linux/iio/buffer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/regulator/consumer.h>

#define ADC084S021_DRIVER_NAME "adc084s021"

struct adc084s021 {
        struct spi_device *spi;
        struct spi_message message;
        struct spi_transfer spi_trans;
        struct regulator *reg;
        struct mutex lock;
        /*
         * DMA (thus cache coherency maintenance) requires the
         * transfer buffers to live in their own cache line.
         */
        u16 tx_buf[4] ____cacheline_aligned;
        __be16 rx_buf[5]; /* First 16-bits are trash */
};

#define ADC084S021_VOLTAGE_CHANNEL(num)                  \
        {                                                      \
                .type = IIO_VOLTAGE,                                 \
                .channel = (num),                                    \
                .indexed = 1,                                        \
                .scan_index = (num),                                 \
                .scan_type = {                                       \
                        .sign = 'u',                                       \
                        .realbits = 8,                                     \
                        .storagebits = 16,                                 \
                        .shift = 4,                                        \
                        .endianness = IIO_BE,                              \
                },                                                   \
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),        \
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),\
        }

static const struct iio_chan_spec adc084s021_channels[] = {
        ADC084S021_VOLTAGE_CHANNEL(0),
        ADC084S021_VOLTAGE_CHANNEL(1),
        ADC084S021_VOLTAGE_CHANNEL(2),
        ADC084S021_VOLTAGE_CHANNEL(3),
        IIO_CHAN_SOFT_TIMESTAMP(4),
};

/**
 * Read an ADC channel and return its value.
 *
 * @adc: The ADC SPI data.
 * @data: Buffer for converted data.
 */
static int adc084s021_adc_conversion(struct adc084s021 *adc, void *data)
{
        int n_words = (adc->spi_trans.len >> 1) - 1; /* Discard first word */
        int ret, i = 0;
        u16 *p = data;

        /* Do the transfer */
        ret = spi_sync(adc->spi, &adc->message);
        if (ret < 0)
                return ret;

        for (; i < n_words; i++)
                *(p + i) = adc->rx_buf[i + 1];

        return ret;
}

static int adc084s021_read_raw(struct iio_dev *indio_dev,
                           struct iio_chan_spec const *channel, int *val,
                           int *val2, long mask)
{
        struct adc084s021 *adc = iio_priv(indio_dev);
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                ret = iio_device_claim_direct_mode(indio_dev);
                if (ret < 0)
                        return ret;

                ret = regulator_enable(adc->reg);
                if (ret) {
                        iio_device_release_direct_mode(indio_dev);
                        return ret;
                }

                adc->tx_buf[0] = channel->channel << 3;
                ret = adc084s021_adc_conversion(adc, val);
                iio_device_release_direct_mode(indio_dev);
                regulator_disable(adc->reg);
                if (ret < 0)
                        return ret;

                *val = be16_to_cpu(*val);
                *val = (*val >> channel->scan_type.shift) & 0xff;

                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                ret = regulator_enable(adc->reg);
                if (ret)
                        return ret;

                ret = regulator_get_voltage(adc->reg);
                regulator_disable(adc->reg);
                if (ret < 0)
                        return ret;

                *val = ret / 1000;

                return IIO_VAL_INT;
        default:
                return -EINVAL;
        }
}

/**
 * Read enabled ADC channels and push data to the buffer.
 *
 * @irq: The interrupt number (not used).
 * @pollfunc: Pointer to the poll func.
 */
static irqreturn_t adc084s021_buffer_trigger_handler(int irq, void *pollfunc)
{
        struct iio_poll_func *pf = pollfunc;
        struct iio_dev *indio_dev = pf->indio_dev;
        struct adc084s021 *adc = iio_priv(indio_dev);
        __be16 data[8] = {0}; /* 4 * 16-bit words of data + 8 bytes timestamp */

        mutex_lock(&adc->lock);

        if (adc084s021_adc_conversion(adc, &data) < 0)
                dev_err(&adc->spi->dev, "Failed to read data\n");

        iio_push_to_buffers_with_timestamp(indio_dev, data,
                                           iio_get_time_ns(indio_dev));
        mutex_unlock(&adc->lock);
        iio_trigger_notify_done(indio_dev->trig);

        return IRQ_HANDLED;
}

static int adc084s021_buffer_preenable(struct iio_dev *indio_dev)
{
        struct adc084s021 *adc = iio_priv(indio_dev);
        int scan_index;
        int i = 0;

        for_each_set_bit(scan_index, indio_dev->active_scan_mask,
                         indio_dev->masklength) {
                const struct iio_chan_spec *channel =
                        &indio_dev->channels[scan_index];
                adc->tx_buf[i++] = channel->channel << 3;
        }
        adc->spi_trans.len = 2 + (i * sizeof(__be16)); /* Trash + channels */

        return regulator_enable(adc->reg);
}

static int adc084s021_buffer_postdisable(struct iio_dev *indio_dev)
{
        struct adc084s021 *adc = iio_priv(indio_dev);

        adc->spi_trans.len = 4; /* Trash + single channel */

        return regulator_disable(adc->reg);
}

static const struct iio_info adc084s021_info = {
        .read_raw = adc084s021_read_raw,
};

static const struct iio_buffer_setup_ops adc084s021_buffer_setup_ops = {
        .preenable = adc084s021_buffer_preenable,
        .postenable = iio_triggered_buffer_postenable,
        .predisable = iio_triggered_buffer_predisable,
        .postdisable = adc084s021_buffer_postdisable,
};

static int adc084s021_probe(struct spi_device *spi)
{
        struct iio_dev *indio_dev;
        struct adc084s021 *adc;
        int ret;

        indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
        if (!indio_dev) {
                dev_err(&spi->dev, "Failed to allocate IIO device\n");
                return -ENOMEM;
        }

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

        /* Connect the SPI device and the iio dev */
        spi_set_drvdata(spi, indio_dev);

        /* Initiate the Industrial I/O device */
        indio_dev->dev.parent = &spi->dev;
        indio_dev->dev.of_node = spi->dev.of_node;
        indio_dev->name = spi_get_device_id(spi)->name;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->info = &adc084s021_info;
        indio_dev->channels = adc084s021_channels;
        indio_dev->num_channels = ARRAY_SIZE(adc084s021_channels);

        /* Create SPI transfer for channel reads */
        adc->spi_trans.tx_buf = adc->tx_buf;
        adc->spi_trans.rx_buf = adc->rx_buf;
        adc->spi_trans.len = 4; /* Trash + single channel */
        spi_message_init_with_transfers(&adc->message, &adc->spi_trans, 1);

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

        mutex_init(&adc->lock);

        /* Setup triggered buffer with pollfunction */
        ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev, NULL,
                                            adc084s021_buffer_trigger_handler,
                                            &adc084s021_buffer_setup_ops);
        if (ret) {
                dev_err(&spi->dev, "Failed to setup triggered buffer\n");
                return ret;
        }

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

static const struct of_device_id adc084s021_of_match[] = {
        { .compatible = "ti,adc084s021", },
        {},
};
MODULE_DEVICE_TABLE(of, adc084s021_of_match);

static const struct spi_device_id adc084s021_id[] = {
        { ADC084S021_DRIVER_NAME, 0},
        {}
};
MODULE_DEVICE_TABLE(spi, adc084s021_id);

static struct spi_driver adc084s021_driver = {
        .driver = {
                .name = ADC084S021_DRIVER_NAME,
                .of_match_table = of_match_ptr(adc084s021_of_match),
        },
        .probe = adc084s021_probe,
        .id_table = adc084s021_id,
};
module_spi_driver(adc084s021_driver);

MODULE_AUTHOR("Mårten Lindahl <martenli@axis.com>");
MODULE_DESCRIPTION("Texas Instruments ADC084S021");
MODULE_LICENSE("GPL v2");
MODULE_VERSION("1.0");