/*
 * TI ADC108S102 SPI ADC driver
 *
 * Copyright (c) 2013-2015 Intel Corporation.
 * Copyright (c) 2017 Siemens AG
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * This IIO device driver is designed to work with the following
 * analog to digital converters from Texas Instruments:
 *  ADC108S102
 *  ADC128S102
 * The communication with ADC chip is via the SPI bus (mode 3).
 */

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

/*
 * In case of ACPI, we use the hard-wired 5000 mV of the Galileo and IOT2000
 * boards as default for the reference pin VA. Device tree users encode that
 * via the vref-supply regulator.
 */
#define ADC108S102_VA_MV_ACPI_DEFAULT   5000

/*
 * Defining the ADC resolution being 12 bits, we can use the same driver for
 * both ADC108S102 (10 bits resolution) and ADC128S102 (12 bits resolution)
 * chips. The ADC108S102 effectively returns a 12-bit result with the 2
 * least-significant bits unset.
 */
#define ADC108S102_BITS         12
#define ADC108S102_MAX_CHANNELS 8

/*
 * 16-bit SPI command format:
 *   [15:14] Ignored
 *   [13:11] 3-bit channel address
 *   [10:0]  Ignored
 */
#define ADC108S102_CMD(ch)              ((u16)(ch) << 11)

/*
 * 16-bit SPI response format:
 *   [15:12] Zeros
 *   [11:0]  12-bit ADC sample (for ADC108S102, [1:0] will always be 0).
 */
#define ADC108S102_RES_DATA(res)        ((u16)res & GENMASK(11, 0))

struct adc108s102_state {
        struct spi_device               *spi;
        struct regulator                *reg;
        u32                             va_millivolt;
        /* SPI transfer used by triggered buffer handler*/
        struct spi_transfer             ring_xfer;
        /* SPI transfer used by direct scan */
        struct spi_transfer             scan_single_xfer;
        /* SPI message used by ring_xfer SPI transfer */
        struct spi_message              ring_msg;
        /* SPI message used by scan_single_xfer SPI transfer */
        struct spi_message              scan_single_msg;

        /*
         * SPI message buffers:
         *  tx_buf: |C0|C1|C2|C3|C4|C5|C6|C7|XX|
         *  rx_buf: |XX|R0|R1|R2|R3|R4|R5|R6|R7|tt|tt|tt|tt|
         *
         *  tx_buf: 8 channel read commands, plus 1 dummy command
         *  rx_buf: 1 dummy response, 8 channel responses, plus 64-bit timestamp
         */
        __be16                          rx_buf[13] ____cacheline_aligned;
        __be16                          tx_buf[9] ____cacheline_aligned;
};

#define ADC108S102_V_CHAN(index)                                        \
        {                                                               \
                .type = IIO_VOLTAGE,                                    \
                .indexed = 1,                                           \
                .channel = index,                                       \
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |          \
                        BIT(IIO_CHAN_INFO_SCALE),                       \
                .address = index,                                       \
                .scan_index = index,                                    \
                .scan_type = {                                          \
                        .sign = 'u',                                    \
                        .realbits = ADC108S102_BITS,                    \
                        .storagebits = 16,                              \
                        .endianness = IIO_BE,                           \
                },                                                      \
        }

static const struct iio_chan_spec adc108s102_channels[] = {
        ADC108S102_V_CHAN(0),
        ADC108S102_V_CHAN(1),
        ADC108S102_V_CHAN(2),
        ADC108S102_V_CHAN(3),
        ADC108S102_V_CHAN(4),
        ADC108S102_V_CHAN(5),
        ADC108S102_V_CHAN(6),
        ADC108S102_V_CHAN(7),
        IIO_CHAN_SOFT_TIMESTAMP(8),
};

static int adc108s102_update_scan_mode(struct iio_dev *indio_dev,
                unsigned long const *active_scan_mask)
{
        struct adc108s102_state *st = iio_priv(indio_dev);
        unsigned int bit, cmds;

        /*
         * Fill in the first x shorts of tx_buf with the number of channels
         * enabled for sampling by the triggered buffer.
         */
        cmds = 0;
        for_each_set_bit(bit, active_scan_mask, ADC108S102_MAX_CHANNELS)
                st->tx_buf[cmds++] = cpu_to_be16(ADC108S102_CMD(bit));

        /* One dummy command added, to clock in the last response */
        st->tx_buf[cmds++] = 0x00;

        /* build SPI ring message */
        st->ring_xfer.tx_buf = &st->tx_buf[0];
        st->ring_xfer.rx_buf = &st->rx_buf[0];
        st->ring_xfer.len = cmds * sizeof(st->tx_buf[0]);

        spi_message_init_with_transfers(&st->ring_msg, &st->ring_xfer, 1);

        return 0;
}

static irqreturn_t adc108s102_trigger_handler(int irq, void *p)
{
        struct iio_poll_func *pf = p;
        struct iio_dev *indio_dev = pf->indio_dev;
        struct adc108s102_state *st = iio_priv(indio_dev);
        int ret;

        ret = spi_sync(st->spi, &st->ring_msg);
        if (ret < 0)
                goto out_notify;

        /* Skip the dummy response in the first slot */
        iio_push_to_buffers_with_timestamp(indio_dev,
                                           (u8 *)&st->rx_buf[1],
                                           iio_get_time_ns(indio_dev));

out_notify:
        iio_trigger_notify_done(indio_dev->trig);

        return IRQ_HANDLED;
}

static int adc108s102_scan_direct(struct adc108s102_state *st, unsigned int ch)
{
        int ret;

        st->tx_buf[0] = cpu_to_be16(ADC108S102_CMD(ch));
        ret = spi_sync(st->spi, &st->scan_single_msg);
        if (ret)
                return ret;

        /* Skip the dummy response in the first slot */
        return be16_to_cpu(st->rx_buf[1]);
}

static int adc108s102_read_raw(struct iio_dev *indio_dev,
                               struct iio_chan_spec const *chan,
                               int *val, int *val2, long m)
{
        struct adc108s102_state *st = iio_priv(indio_dev);
        int ret;

        switch (m) {
        case IIO_CHAN_INFO_RAW:
                ret = iio_device_claim_direct_mode(indio_dev);
                if (ret)
                        return ret;

                ret = adc108s102_scan_direct(st, chan->address);

                iio_device_release_direct_mode(indio_dev);

                if (ret < 0)
                        return ret;

                *val = ADC108S102_RES_DATA(ret);

                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                if (chan->type != IIO_VOLTAGE)
                        break;

                *val = st->va_millivolt;
                *val2 = chan->scan_type.realbits;

                return IIO_VAL_FRACTIONAL_LOG2;
        default:
                break;
        }

        return -EINVAL;
}

static const struct iio_info adc108s102_info = {
        .read_raw               = &adc108s102_read_raw,
        .update_scan_mode       = &adc108s102_update_scan_mode,
};

static int adc108s102_probe(struct spi_device *spi)
{
        struct adc108s102_state *st;
        struct iio_dev *indio_dev;
        int ret;

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

        st = iio_priv(indio_dev);

        if (ACPI_COMPANION(&spi->dev)) {
                st->va_millivolt = ADC108S102_VA_MV_ACPI_DEFAULT;
        } else {
                st->reg = devm_regulator_get(&spi->dev, "vref");
                if (IS_ERR(st->reg))
                        return PTR_ERR(st->reg);

                ret = regulator_enable(st->reg);
                if (ret < 0) {
                        dev_err(&spi->dev, "Cannot enable vref regulator\n");
                        return ret;
                }

                ret = regulator_get_voltage(st->reg);
                if (ret < 0) {
                        dev_err(&spi->dev, "vref get voltage failed\n");
                        return ret;
                }

                st->va_millivolt = ret / 1000;
        }

        spi_set_drvdata(spi, indio_dev);
        st->spi = spi;

        indio_dev->name = spi->modalias;
        indio_dev->dev.parent = &spi->dev;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = adc108s102_channels;
        indio_dev->num_channels = ARRAY_SIZE(adc108s102_channels);
        indio_dev->info = &adc108s102_info;

        /* Setup default message */
        st->scan_single_xfer.tx_buf = st->tx_buf;
        st->scan_single_xfer.rx_buf = st->rx_buf;
        st->scan_single_xfer.len = 2 * sizeof(st->tx_buf[0]);

        spi_message_init_with_transfers(&st->scan_single_msg,
                                        &st->scan_single_xfer, 1);

        ret = iio_triggered_buffer_setup(indio_dev, NULL,
                                         &adc108s102_trigger_handler, NULL);
        if (ret)
                goto error_disable_reg;

        ret = iio_device_register(indio_dev);
        if (ret) {
                dev_err(&spi->dev, "Failed to register IIO device\n");
                goto error_cleanup_triggered_buffer;
        }
        return 0;

error_cleanup_triggered_buffer:
        iio_triggered_buffer_cleanup(indio_dev);

error_disable_reg:
        regulator_disable(st->reg);

        return ret;
}

static int adc108s102_remove(struct spi_device *spi)
{
        struct iio_dev *indio_dev = spi_get_drvdata(spi);
        struct adc108s102_state *st = iio_priv(indio_dev);

        iio_device_unregister(indio_dev);
        iio_triggered_buffer_cleanup(indio_dev);

        regulator_disable(st->reg);

        return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id adc108s102_of_match[] = {
        { .compatible = "ti,adc108s102" },
        { }
};
MODULE_DEVICE_TABLE(of, adc108s102_of_match);
#endif

#ifdef CONFIG_ACPI
static const struct acpi_device_id adc108s102_acpi_ids[] = {
        { "INT3495", 0 },
        { }
};
MODULE_DEVICE_TABLE(acpi, adc108s102_acpi_ids);
#endif

static const struct spi_device_id adc108s102_id[] = {
        { "adc108s102", 0 },
        { }
};
MODULE_DEVICE_TABLE(spi, adc108s102_id);

static struct spi_driver adc108s102_driver = {
        .driver = {
                .name   = "adc108s102",
                .of_match_table = of_match_ptr(adc108s102_of_match),
                .acpi_match_table = ACPI_PTR(adc108s102_acpi_ids),
        },
        .probe          = adc108s102_probe,
        .remove         = adc108s102_remove,
        .id_table       = adc108s102_id,
};
module_spi_driver(adc108s102_driver);

MODULE_AUTHOR("Bogdan Pricop <bogdan.pricop@emutex.com>");
MODULE_DESCRIPTION("Texas Instruments ADC108S102 and ADC128S102 driver");
MODULE_LICENSE("GPL v2");