drm/client: Fix drm client endless Kconfig loop

[drm/drm-misc.git] / drivers / iio / adc / ti-tsc2046.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Texas Instruments TSC2046 SPI ADC driver
 *
 * Copyright (c) 2021 Oleksij Rempel <kernel@pengutronix.de>, Pengutronix
 */

#include <linux/bitfield.h>
#include <linux/cleanup.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/regulator/consumer.h>
#include <linux/spi/spi.h>
#include <linux/units.h>

#include <linux/unaligned.h>

#include <linux/iio/buffer.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/trigger.h>

/*
 * The PENIRQ of TSC2046 controller is implemented as level shifter attached to
 * the X+ line. If voltage of the X+ line reaches a specific level the IRQ will
 * be activated or deactivated.
 * To make this kind of IRQ reusable as trigger following additions were
 * implemented:
 * - rate limiting:
 *   For typical touchscreen use case, we need to trigger about each 10ms.
 * - hrtimer:
 *   Continue triggering at least once after the IRQ was deactivated. Then
 *   deactivate this trigger to stop sampling in order to reduce power
 *   consumption.
 */

#define TI_TSC2046_NAME                         "tsc2046"

/* This driver doesn't aim at the peak continuous sample rate */
#define TI_TSC2046_MAX_SAMPLE_RATE              125000
#define TI_TSC2046_SAMPLE_BITS \
        BITS_PER_TYPE(struct tsc2046_adc_atom)
#define TI_TSC2046_MAX_CLK_FREQ \
        (TI_TSC2046_MAX_SAMPLE_RATE * TI_TSC2046_SAMPLE_BITS)

#define TI_TSC2046_SAMPLE_INTERVAL_US           10000

#define TI_TSC2046_START                        BIT(7)
#define TI_TSC2046_ADDR                         GENMASK(6, 4)
#define TI_TSC2046_ADDR_TEMP1                   7
#define TI_TSC2046_ADDR_AUX                     6
#define TI_TSC2046_ADDR_X                       5
#define TI_TSC2046_ADDR_Z2                      4
#define TI_TSC2046_ADDR_Z1                      3
#define TI_TSC2046_ADDR_VBAT                    2
#define TI_TSC2046_ADDR_Y                       1
#define TI_TSC2046_ADDR_TEMP0                   0

/*
 * The mode bit sets the resolution of the ADC. With this bit low, the next
 * conversion has 12-bit resolution, whereas with this bit high, the next
 * conversion has 8-bit resolution. This driver is optimized for 12-bit mode.
 * So, for this driver, this bit should stay zero.
 */
#define TI_TSC2046_8BIT_MODE                    BIT(3)

/*
 * SER/DFR - The SER/DFR bit controls the reference mode, either single-ended
 * (high) or differential (low).
 */
#define TI_TSC2046_SER                          BIT(2)

/*
 * If VREF_ON and ADC_ON are both zero, then the chip operates in
 * auto-wake/suspend mode. In most case this bits should stay zero.
 */
#define TI_TSC2046_PD1_VREF_ON                  BIT(1)
#define TI_TSC2046_PD0_ADC_ON                   BIT(0)

/*
 * All supported devices can do 8 or 12bit resolution. This driver
 * supports only 12bit mode, here we have a 16bit data transfer, where
 * the MSB and the 3 LSB are 0.
 */
#define TI_TSC2046_DATA_12BIT                   GENMASK(14, 3)

#define TI_TSC2046_MAX_CHAN                     8
#define TI_TSC2046_MIN_POLL_CNT                 3
#define TI_TSC2046_EXT_POLL_CNT                 3
#define TI_TSC2046_POLL_CNT \
        (TI_TSC2046_MIN_POLL_CNT + TI_TSC2046_EXT_POLL_CNT)
#define TI_TSC2046_INT_VREF                     2500

/* Represents a HW sample */
struct tsc2046_adc_atom {
        /*
         * Command transmitted to the controller. This field is empty on the RX
         * buffer.
         */
        u8 cmd;
        /*
         * Data received from the controller. This field is empty for the TX
         * buffer
         */
        __be16 data;
} __packed;

/* Layout of atomic buffers within big buffer */
struct tsc2046_adc_group_layout {
        /* Group offset within the SPI RX buffer */
        unsigned int offset;
        /*
         * Amount of tsc2046_adc_atom structs within the same command gathered
         * within same group.
         */
        unsigned int count;
        /*
         * Settling samples (tsc2046_adc_atom structs) which should be skipped
         * before good samples will start.
         */
        unsigned int skip;
};

struct tsc2046_adc_dcfg {
        const struct iio_chan_spec *channels;
        unsigned int num_channels;
};

struct tsc2046_adc_ch_cfg {
        unsigned int settling_time_us;
        unsigned int oversampling_ratio;
};

enum tsc2046_state {
        TSC2046_STATE_SHUTDOWN,
        TSC2046_STATE_STANDBY,
        TSC2046_STATE_POLL,
        TSC2046_STATE_POLL_IRQ_DISABLE,
        TSC2046_STATE_ENABLE_IRQ,
};

struct tsc2046_adc_priv {
        struct spi_device *spi;
        const struct tsc2046_adc_dcfg *dcfg;
        bool internal_vref;

        struct iio_trigger *trig;
        struct hrtimer trig_timer;
        enum tsc2046_state state;
        int poll_cnt;
        spinlock_t state_lock;

        struct spi_transfer xfer;
        struct spi_message msg;

        struct {
                /* Scan data for each channel */
                u16 data[TI_TSC2046_MAX_CHAN];
                /* Timestamp */
                s64 ts __aligned(8);
        } scan_buf;

        /*
         * Lock to protect the layout and the SPI transfer buffer.
         * tsc2046_adc_group_layout can be changed within update_scan_mode(),
         * in this case the l[] and tx/rx buffer will be out of sync to each
         * other.
         */
        struct mutex slock;
        struct tsc2046_adc_group_layout l[TI_TSC2046_MAX_CHAN];
        struct tsc2046_adc_atom *rx;
        struct tsc2046_adc_atom *tx;

        unsigned int count;
        unsigned int groups;
        u32 effective_speed_hz;
        u32 scan_interval_us;
        u32 time_per_scan_us;
        u32 time_per_bit_ns;
        unsigned int vref_mv;

        struct tsc2046_adc_ch_cfg ch_cfg[TI_TSC2046_MAX_CHAN];
};

#define TI_TSC2046_V_CHAN(index, bits, name)                    \
{                                                               \
        .type = IIO_VOLTAGE,                                    \
        .indexed = 1,                                           \
        .channel = index,                                       \
        .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),           \
        .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),   \
        .datasheet_name = "#name",                              \
        .scan_index = index,                                    \
        .scan_type = {                                          \
                .sign = 'u',                                    \
                .realbits = bits,                               \
                .storagebits = 16,                              \
                .endianness = IIO_CPU,                          \
        },                                                      \
}

#define DECLARE_TI_TSC2046_8_CHANNELS(name, bits) \
const struct iio_chan_spec name ## _channels[] = { \
        TI_TSC2046_V_CHAN(0, bits, TEMP0), \
        TI_TSC2046_V_CHAN(1, bits, Y), \
        TI_TSC2046_V_CHAN(2, bits, VBAT), \
        TI_TSC2046_V_CHAN(3, bits, Z1), \
        TI_TSC2046_V_CHAN(4, bits, Z2), \
        TI_TSC2046_V_CHAN(5, bits, X), \
        TI_TSC2046_V_CHAN(6, bits, AUX), \
        TI_TSC2046_V_CHAN(7, bits, TEMP1), \
        IIO_CHAN_SOFT_TIMESTAMP(8), \
}

static DECLARE_TI_TSC2046_8_CHANNELS(tsc2046_adc, 12);

static const struct tsc2046_adc_dcfg tsc2046_adc_dcfg_tsc2046e = {
        .channels = tsc2046_adc_channels,
        .num_channels = ARRAY_SIZE(tsc2046_adc_channels),
};

/*
 * Convert time to a number of samples which can be transferred within this
 * time.
 */
static unsigned int tsc2046_adc_time_to_count(struct tsc2046_adc_priv *priv,
                                              unsigned long time)
{
        unsigned int bit_count, sample_count;

        bit_count = DIV_ROUND_UP(time * NSEC_PER_USEC, priv->time_per_bit_ns);
        sample_count = DIV_ROUND_UP(bit_count, TI_TSC2046_SAMPLE_BITS);

        dev_dbg(&priv->spi->dev, "Effective speed %u, time per bit: %u, count bits: %u, count samples: %u\n",
                priv->effective_speed_hz, priv->time_per_bit_ns,
                bit_count, sample_count);

        return sample_count;
}

static u8 tsc2046_adc_get_cmd(struct tsc2046_adc_priv *priv, int ch_idx,
                              bool keep_power)
{
        u32 pd;

        /*
         * if PD bits are 0, controller will automatically disable ADC, VREF and
         * enable IRQ.
         */
        if (keep_power)
                pd = TI_TSC2046_PD0_ADC_ON;
        else
                pd = 0;

        switch (ch_idx) {
        case TI_TSC2046_ADDR_TEMP1:
        case TI_TSC2046_ADDR_AUX:
        case TI_TSC2046_ADDR_VBAT:
        case TI_TSC2046_ADDR_TEMP0:
                pd |= TI_TSC2046_SER;
                if (priv->internal_vref)
                        pd |= TI_TSC2046_PD1_VREF_ON;
        }

        return TI_TSC2046_START | FIELD_PREP(TI_TSC2046_ADDR, ch_idx) | pd;
}

static u16 tsc2046_adc_get_value(struct tsc2046_adc_atom *buf)
{
        return FIELD_GET(TI_TSC2046_DATA_12BIT, get_unaligned_be16(&buf->data));
}

static int tsc2046_adc_read_one(struct tsc2046_adc_priv *priv, int ch_idx,
                                u32 *effective_speed_hz)
{
        struct tsc2046_adc_ch_cfg *ch = &priv->ch_cfg[ch_idx];
        unsigned int val, val_normalized = 0;
        int ret, i, count_skip = 0, max_count;
        struct spi_transfer xfer;
        struct spi_message msg;
        u8 cmd;

        if (!effective_speed_hz) {
                count_skip = tsc2046_adc_time_to_count(priv, ch->settling_time_us);
                max_count = count_skip + ch->oversampling_ratio;
        } else {
                max_count = 1;
        }

        if (sizeof(struct tsc2046_adc_atom) * max_count > PAGE_SIZE)
                return -ENOSPC;

        struct tsc2046_adc_atom *tx_buf __free(kfree) = kcalloc(max_count,
                                                                sizeof(*tx_buf),
                                                                GFP_KERNEL);
        if (!tx_buf)
                return -ENOMEM;

        struct tsc2046_adc_atom *rx_buf __free(kfree) = kcalloc(max_count,
                                                                sizeof(*rx_buf),
                                                                GFP_KERNEL);
        if (!rx_buf)
                return -ENOMEM;

        /*
         * Do not enable automatic power down on working samples. Otherwise the
         * plates will never be completely charged.
         */
        cmd = tsc2046_adc_get_cmd(priv, ch_idx, true);

        for (i = 0; i < max_count - 1; i++)
                tx_buf[i].cmd = cmd;

        /* automatically power down on last sample */
        tx_buf[i].cmd = tsc2046_adc_get_cmd(priv, ch_idx, false);

        memset(&xfer, 0, sizeof(xfer));
        xfer.tx_buf = tx_buf;
        xfer.rx_buf = rx_buf;
        xfer.len = sizeof(*tx_buf) * max_count;
        spi_message_init_with_transfers(&msg, &xfer, 1);

        /*
         * We aren't using spi_write_then_read() because we need to be able
         * to get hold of the effective_speed_hz from the xfer
         */
        ret = spi_sync(priv->spi, &msg);
        if (ret) {
                dev_err_ratelimited(&priv->spi->dev, "SPI transfer failed %pe\n",
                                    ERR_PTR(ret));
                return ret;
        }

        if (effective_speed_hz)
                *effective_speed_hz = xfer.effective_speed_hz;

        for (i = 0; i < max_count - count_skip; i++) {
                val = tsc2046_adc_get_value(&rx_buf[count_skip + i]);
                val_normalized += val;
        }

        return DIV_ROUND_UP(val_normalized, max_count - count_skip);
}

static size_t tsc2046_adc_group_set_layout(struct tsc2046_adc_priv *priv,
                                           unsigned int group,
                                           unsigned int ch_idx)
{
        struct tsc2046_adc_ch_cfg *ch = &priv->ch_cfg[ch_idx];
        struct tsc2046_adc_group_layout *cur;
        unsigned int max_count, count_skip;
        unsigned int offset = 0;

        if (group)
                offset = priv->l[group - 1].offset + priv->l[group - 1].count;

        count_skip = tsc2046_adc_time_to_count(priv, ch->settling_time_us);
        max_count = count_skip + ch->oversampling_ratio;

        cur = &priv->l[group];
        cur->offset = offset;
        cur->count = max_count;
        cur->skip = count_skip;

        return sizeof(*priv->tx) * max_count;
}

static void tsc2046_adc_group_set_cmd(struct tsc2046_adc_priv *priv,
                                      unsigned int group, int ch_idx)
{
        struct tsc2046_adc_group_layout *l = &priv->l[group];
        unsigned int i;
        u8 cmd;

        /*
         * Do not enable automatic power down on working samples. Otherwise the
         * plates will never be completely charged.
         */
        cmd = tsc2046_adc_get_cmd(priv, ch_idx, true);

        for (i = 0; i < l->count - 1; i++)
                priv->tx[l->offset + i].cmd = cmd;

        /* automatically power down on last sample */
        priv->tx[l->offset + i].cmd = tsc2046_adc_get_cmd(priv, ch_idx, false);
}

static u16 tsc2046_adc_get_val(struct tsc2046_adc_priv *priv, int group)
{
        struct tsc2046_adc_group_layout *l;
        unsigned int val, val_normalized = 0;
        int valid_count, i;

        l = &priv->l[group];
        valid_count = l->count - l->skip;

        for (i = 0; i < valid_count; i++) {
                val = tsc2046_adc_get_value(&priv->rx[l->offset + l->skip + i]);
                val_normalized += val;
        }

        return DIV_ROUND_UP(val_normalized, valid_count);
}

static int tsc2046_adc_scan(struct iio_dev *indio_dev)
{
        struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
        struct device *dev = &priv->spi->dev;
        int group;
        int ret;

        ret = spi_sync(priv->spi, &priv->msg);
        if (ret < 0) {
                dev_err_ratelimited(dev, "SPI transfer failed: %pe\n", ERR_PTR(ret));
                return ret;
        }

        for (group = 0; group < priv->groups; group++)
                priv->scan_buf.data[group] = tsc2046_adc_get_val(priv, group);

        ret = iio_push_to_buffers_with_timestamp(indio_dev, &priv->scan_buf,
                                                 iio_get_time_ns(indio_dev));
        /* If the consumer is kfifo, we may get a EBUSY here - ignore it. */
        if (ret < 0 && ret != -EBUSY) {
                dev_err_ratelimited(dev, "Failed to push scan buffer %pe\n",
                                    ERR_PTR(ret));

                return ret;
        }

        return 0;
}

static irqreturn_t tsc2046_adc_trigger_handler(int irq, void *p)
{
        struct iio_poll_func *pf = p;
        struct iio_dev *indio_dev = pf->indio_dev;
        struct tsc2046_adc_priv *priv = iio_priv(indio_dev);

        mutex_lock(&priv->slock);
        tsc2046_adc_scan(indio_dev);
        mutex_unlock(&priv->slock);

        iio_trigger_notify_done(indio_dev->trig);

        return IRQ_HANDLED;
}

static int tsc2046_adc_read_raw(struct iio_dev *indio_dev,
                                struct iio_chan_spec const *chan,
                                int *val, int *val2, long m)
{
        struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
        int ret;

        switch (m) {
        case IIO_CHAN_INFO_RAW:
                ret = tsc2046_adc_read_one(priv, chan->channel, NULL);
                if (ret < 0)
                        return ret;

                *val = ret;

                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                /*
                 * Note: the TSC2046 has internal voltage divider on the VBAT
                 * line. This divider can be influenced by external divider.
                 * So, it is better to use external voltage-divider driver
                 * instead, which is calculating complete chain.
                 */
                *val = priv->vref_mv;
                *val2 = chan->scan_type.realbits;
                return IIO_VAL_FRACTIONAL_LOG2;
        }

        return -EINVAL;
}

static int tsc2046_adc_update_scan_mode(struct iio_dev *indio_dev,
                                        const unsigned long *active_scan_mask)
{
        struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
        unsigned int ch_idx, group = 0;
        size_t size;

        mutex_lock(&priv->slock);

        size = 0;
        for_each_set_bit(ch_idx, active_scan_mask, ARRAY_SIZE(priv->l)) {
                size += tsc2046_adc_group_set_layout(priv, group, ch_idx);
                tsc2046_adc_group_set_cmd(priv, group, ch_idx);
                group++;
        }

        priv->groups = group;
        priv->xfer.len = size;
        priv->time_per_scan_us = size * 8 * priv->time_per_bit_ns / NSEC_PER_USEC;

        if (priv->scan_interval_us < priv->time_per_scan_us)
                dev_warn(&priv->spi->dev, "The scan interval (%d) is less then calculated scan time (%d)\n",
                         priv->scan_interval_us, priv->time_per_scan_us);

        mutex_unlock(&priv->slock);

        return 0;
}

static const struct iio_info tsc2046_adc_info = {
        .read_raw         = tsc2046_adc_read_raw,
        .update_scan_mode = tsc2046_adc_update_scan_mode,
};

static enum hrtimer_restart tsc2046_adc_timer(struct hrtimer *hrtimer)
{
        struct tsc2046_adc_priv *priv = container_of(hrtimer,
                                                     struct tsc2046_adc_priv,
                                                     trig_timer);
        unsigned long flags;

        /*
         * This state machine should address following challenges :
         * - the interrupt source is based on level shifter attached to the X
         *   channel of ADC. It will change the state every time we switch
         *   between channels. So, we need to disable IRQ if we do
         *   iio_trigger_poll().
         * - we should do iio_trigger_poll() at some reduced sample rate
         * - we should still trigger for some amount of time after last
         *   interrupt with enabled IRQ was processed.
         */

        spin_lock_irqsave(&priv->state_lock, flags);
        switch (priv->state) {
        case TSC2046_STATE_ENABLE_IRQ:
                if (priv->poll_cnt < TI_TSC2046_POLL_CNT) {
                        priv->poll_cnt++;
                        hrtimer_start(&priv->trig_timer,
                                      ns_to_ktime(priv->scan_interval_us *
                                                  NSEC_PER_USEC),
                                      HRTIMER_MODE_REL_SOFT);

                        if (priv->poll_cnt >= TI_TSC2046_MIN_POLL_CNT) {
                                priv->state = TSC2046_STATE_POLL_IRQ_DISABLE;
                                enable_irq(priv->spi->irq);
                        } else {
                                priv->state = TSC2046_STATE_POLL;
                        }
                } else {
                        priv->state = TSC2046_STATE_STANDBY;
                        enable_irq(priv->spi->irq);
                }
                break;
        case TSC2046_STATE_POLL_IRQ_DISABLE:
                disable_irq_nosync(priv->spi->irq);
                fallthrough;
        case TSC2046_STATE_POLL:
                priv->state = TSC2046_STATE_ENABLE_IRQ;
                /* iio_trigger_poll() starts hrtimer */
                iio_trigger_poll(priv->trig);
                break;
        case TSC2046_STATE_SHUTDOWN:
                break;
        case TSC2046_STATE_STANDBY:
                fallthrough;
        default:
                dev_warn(&priv->spi->dev, "Got unexpected state: %i\n",
                         priv->state);
                break;
        }
        spin_unlock_irqrestore(&priv->state_lock, flags);

        return HRTIMER_NORESTART;
}

static irqreturn_t tsc2046_adc_irq(int irq, void *dev_id)
{
        struct iio_dev *indio_dev = dev_id;
        struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
        unsigned long flags;

        hrtimer_try_to_cancel(&priv->trig_timer);

        spin_lock_irqsave(&priv->state_lock, flags);
        if (priv->state != TSC2046_STATE_SHUTDOWN) {
                priv->state = TSC2046_STATE_ENABLE_IRQ;
                priv->poll_cnt = 0;

                /* iio_trigger_poll() starts hrtimer */
                disable_irq_nosync(priv->spi->irq);
                iio_trigger_poll(priv->trig);
        }
        spin_unlock_irqrestore(&priv->state_lock, flags);

        return IRQ_HANDLED;
}

static void tsc2046_adc_reenable_trigger(struct iio_trigger *trig)
{
        struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
        struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
        ktime_t tim;

        /*
         * We can sample it as fast as we can, but usually we do not need so
         * many samples. Reduce the sample rate for default (touchscreen) use
         * case.
         */
        tim = ns_to_ktime((priv->scan_interval_us - priv->time_per_scan_us) *
                          NSEC_PER_USEC);
        hrtimer_start(&priv->trig_timer, tim, HRTIMER_MODE_REL_SOFT);
}

static int tsc2046_adc_set_trigger_state(struct iio_trigger *trig, bool enable)
{
        struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
        struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
        unsigned long flags;

        if (enable) {
                spin_lock_irqsave(&priv->state_lock, flags);
                if (priv->state == TSC2046_STATE_SHUTDOWN) {
                        priv->state = TSC2046_STATE_STANDBY;
                        enable_irq(priv->spi->irq);
                }
                spin_unlock_irqrestore(&priv->state_lock, flags);
        } else {
                spin_lock_irqsave(&priv->state_lock, flags);

                if (priv->state == TSC2046_STATE_STANDBY ||
                    priv->state == TSC2046_STATE_POLL_IRQ_DISABLE)
                        disable_irq_nosync(priv->spi->irq);

                priv->state = TSC2046_STATE_SHUTDOWN;
                spin_unlock_irqrestore(&priv->state_lock, flags);

                hrtimer_cancel(&priv->trig_timer);
        }

        return 0;
}

static const struct iio_trigger_ops tsc2046_adc_trigger_ops = {
        .set_trigger_state = tsc2046_adc_set_trigger_state,
        .reenable = tsc2046_adc_reenable_trigger,
};

static int tsc2046_adc_setup_spi_msg(struct tsc2046_adc_priv *priv)
{
        unsigned int ch_idx;
        size_t size;
        int ret;

        /*
         * Make dummy read to set initial power state and get real SPI clock
         * freq. It seems to be not important which channel is used for this
         * case.
         */
        ret = tsc2046_adc_read_one(priv, TI_TSC2046_ADDR_TEMP0,
                                   &priv->effective_speed_hz);
        if (ret < 0)
                return ret;

        /*
         * In case SPI controller do not report effective_speed_hz, use
         * configure value and hope it will match.
         */
        if (!priv->effective_speed_hz)
                priv->effective_speed_hz = priv->spi->max_speed_hz;


        priv->scan_interval_us = TI_TSC2046_SAMPLE_INTERVAL_US;
        priv->time_per_bit_ns = DIV_ROUND_UP(NSEC_PER_SEC,
                                             priv->effective_speed_hz);

        /*
         * Calculate and allocate maximal size buffer if all channels are
         * enabled.
         */
        size = 0;
        for (ch_idx = 0; ch_idx < ARRAY_SIZE(priv->l); ch_idx++)
                size += tsc2046_adc_group_set_layout(priv, ch_idx, ch_idx);

        if (size > PAGE_SIZE) {
                dev_err(&priv->spi->dev,
                        "Calculated scan buffer is too big. Try to reduce spi-max-frequency, settling-time-us or oversampling-ratio\n");
                return -ENOSPC;
        }

        priv->tx = devm_kzalloc(&priv->spi->dev, size, GFP_KERNEL);
        if (!priv->tx)
                return -ENOMEM;

        priv->rx = devm_kzalloc(&priv->spi->dev, size, GFP_KERNEL);
        if (!priv->rx)
                return -ENOMEM;

        priv->xfer.tx_buf = priv->tx;
        priv->xfer.rx_buf = priv->rx;
        priv->xfer.len = size;
        spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1);

        return 0;
}

static void tsc2046_adc_parse_fwnode(struct tsc2046_adc_priv *priv)
{
        struct fwnode_handle *child;
        struct device *dev = &priv->spi->dev;
        unsigned int i;

        for (i = 0; i < ARRAY_SIZE(priv->ch_cfg); i++) {
                priv->ch_cfg[i].settling_time_us = 1;
                priv->ch_cfg[i].oversampling_ratio = 1;
        }

        device_for_each_child_node(dev, child) {
                u32 stl, overs, reg;
                int ret;

                ret = fwnode_property_read_u32(child, "reg", &reg);
                if (ret) {
                        dev_err(dev, "invalid reg on %pfw, err: %pe\n", child,
                                ERR_PTR(ret));
                        continue;
                }

                if (reg >= ARRAY_SIZE(priv->ch_cfg)) {
                        dev_err(dev, "%pfw: Unsupported reg value: %i, max supported is: %zu.\n",
                                child, reg, ARRAY_SIZE(priv->ch_cfg));
                        continue;
                }

                ret = fwnode_property_read_u32(child, "settling-time-us", &stl);
                if (!ret)
                        priv->ch_cfg[reg].settling_time_us = stl;

                ret = fwnode_property_read_u32(child, "oversampling-ratio",
                                               &overs);
                if (!ret)
                        priv->ch_cfg[reg].oversampling_ratio = overs;
        }
}

static int tsc2046_adc_probe(struct spi_device *spi)
{
        const struct tsc2046_adc_dcfg *dcfg;
        struct device *dev = &spi->dev;
        struct tsc2046_adc_priv *priv;
        struct iio_dev *indio_dev;
        struct iio_trigger *trig;
        int ret;

        if (spi->max_speed_hz > TI_TSC2046_MAX_CLK_FREQ) {
                dev_err(dev, "SPI max_speed_hz is too high: %d Hz. Max supported freq is %zu Hz\n",
                        spi->max_speed_hz, TI_TSC2046_MAX_CLK_FREQ);
                return -EINVAL;
        }

        dcfg = spi_get_device_match_data(spi);
        if (!dcfg)
                return -EINVAL;

        spi->bits_per_word = 8;
        spi->mode &= ~SPI_MODE_X_MASK;
        spi->mode |= SPI_MODE_0;
        ret = spi_setup(spi);
        if (ret < 0)
                return dev_err_probe(dev, ret, "Error in SPI setup\n");

        indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
        if (!indio_dev)
                return -ENOMEM;

        priv = iio_priv(indio_dev);
        priv->dcfg = dcfg;

        priv->spi = spi;

        indio_dev->name = TI_TSC2046_NAME;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = dcfg->channels;
        indio_dev->num_channels = dcfg->num_channels;
        indio_dev->info = &tsc2046_adc_info;

        ret = devm_regulator_get_enable_read_voltage(dev, "vref");
        if (ret < 0 && ret != -ENODEV)
                return ret;

        priv->internal_vref = ret == -ENODEV;
        priv->vref_mv = priv->internal_vref ? TI_TSC2046_INT_VREF : ret / MILLI;

        tsc2046_adc_parse_fwnode(priv);

        ret = tsc2046_adc_setup_spi_msg(priv);
        if (ret)
                return ret;

        mutex_init(&priv->slock);

        ret = devm_request_irq(dev, spi->irq, &tsc2046_adc_irq,
                               IRQF_NO_AUTOEN, indio_dev->name, indio_dev);
        if (ret)
                return ret;

        trig = devm_iio_trigger_alloc(dev, "touchscreen-%s", indio_dev->name);
        if (!trig)
                return -ENOMEM;

        priv->trig = trig;
        iio_trigger_set_drvdata(trig, indio_dev);
        trig->ops = &tsc2046_adc_trigger_ops;

        spin_lock_init(&priv->state_lock);
        priv->state = TSC2046_STATE_SHUTDOWN;
        hrtimer_init(&priv->trig_timer, CLOCK_MONOTONIC,
                     HRTIMER_MODE_REL_SOFT);
        priv->trig_timer.function = tsc2046_adc_timer;

        ret = devm_iio_trigger_register(dev, trig);
        if (ret) {
                dev_err(dev, "failed to register trigger\n");
                return ret;
        }

        ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
                                              &tsc2046_adc_trigger_handler, NULL);
        if (ret) {
                dev_err(dev, "Failed to setup triggered buffer\n");
                return ret;
        }

        /* set default trigger */
        indio_dev->trig = iio_trigger_get(priv->trig);

        return devm_iio_device_register(dev, indio_dev);
}

static const struct of_device_id ads7950_of_table[] = {
        { .compatible = "ti,tsc2046e-adc", .data = &tsc2046_adc_dcfg_tsc2046e },
        { }
};
MODULE_DEVICE_TABLE(of, ads7950_of_table);

static const struct spi_device_id tsc2046_adc_spi_ids[] = {
        { "tsc2046e-adc", (unsigned long)&tsc2046_adc_dcfg_tsc2046e },
        { }
};
MODULE_DEVICE_TABLE(spi, tsc2046_adc_spi_ids);

static struct spi_driver tsc2046_adc_driver = {
        .driver = {
                .name = "tsc2046",
                .of_match_table = ads7950_of_table,
        },
        .id_table = tsc2046_adc_spi_ids,
        .probe = tsc2046_adc_probe,
};
module_spi_driver(tsc2046_adc_driver);

MODULE_AUTHOR("Oleksij Rempel <kernel@pengutronix.de>");
MODULE_DESCRIPTION("TI TSC2046 ADC");
MODULE_LICENSE("GPL v2");