/*
 * Freescale i.MX28 LRADC driver
 *
 * Copyright (c) 2012 DENX Software Engineering, GmbH.
 * Marek Vasut <marex@denx.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that 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.
 */

#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/sysfs.h>
#include <linux/list.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/stmp_device.h>
#include <linux/bitops.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/input.h>

#include <mach/mxs.h>
#include <mach/common.h>

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

#define DRIVER_NAME             "mxs-lradc"

#define LRADC_MAX_DELAY_CHANS   4
#define LRADC_MAX_MAPPED_CHANS  8
#define LRADC_MAX_TOTAL_CHANS   16

#define LRADC_DELAY_TIMER_HZ    2000

/*
 * Make this runtime configurable if necessary. Currently, if the buffered mode
 * is enabled, the LRADC takes LRADC_DELAY_TIMER_LOOP samples of data before
 * triggering IRQ. The sampling happens every (LRADC_DELAY_TIMER_PER / 2000)
 * seconds. The result is that the samples arrive every 500mS.
 */
#define LRADC_DELAY_TIMER_PER   200
#define LRADC_DELAY_TIMER_LOOP  5

/*
 * Once the pen touches the touchscreen, the touchscreen switches from
 * IRQ-driven mode to polling mode to prevent interrupt storm. The polling
 * is realized by worker thread, which is called every 20 or so milliseconds.
 * This gives the touchscreen enough fluence and does not strain the system
 * too much.
 */
#define LRADC_TS_SAMPLE_DELAY_MS        5

/*
 * The LRADC reads the following amount of samples from each touchscreen
 * channel and the driver then computes avarage of these.
 */
#define LRADC_TS_SAMPLE_AMOUNT          4

enum mxs_lradc_id {
        IMX23_LRADC,
        IMX28_LRADC,
};

static const char * const mx23_lradc_irq_names[] = {
        "mxs-lradc-touchscreen",
        "mxs-lradc-channel0",
        "mxs-lradc-channel1",
        "mxs-lradc-channel2",
        "mxs-lradc-channel3",
        "mxs-lradc-channel4",
        "mxs-lradc-channel5",
        "mxs-lradc-channel6",
        "mxs-lradc-channel7",
};

static const char * const mx28_lradc_irq_names[] = {
        "mxs-lradc-touchscreen",
        "mxs-lradc-thresh0",
        "mxs-lradc-thresh1",
        "mxs-lradc-channel0",
        "mxs-lradc-channel1",
        "mxs-lradc-channel2",
        "mxs-lradc-channel3",
        "mxs-lradc-channel4",
        "mxs-lradc-channel5",
        "mxs-lradc-channel6",
        "mxs-lradc-channel7",
        "mxs-lradc-button0",
        "mxs-lradc-button1",
};

struct mxs_lradc_of_config {
        const int               irq_count;
        const char * const      *irq_name;
};

static const struct mxs_lradc_of_config mxs_lradc_of_config[] = {
        [IMX23_LRADC] = {
                .irq_count      = ARRAY_SIZE(mx23_lradc_irq_names),
                .irq_name       = mx23_lradc_irq_names,
        },
        [IMX28_LRADC] = {
                .irq_count      = ARRAY_SIZE(mx28_lradc_irq_names),
                .irq_name       = mx28_lradc_irq_names,
        },
};

enum mxs_lradc_ts {
        MXS_LRADC_TOUCHSCREEN_NONE = 0,
        MXS_LRADC_TOUCHSCREEN_4WIRE,
        MXS_LRADC_TOUCHSCREEN_5WIRE,
};

struct mxs_lradc {
        struct device           *dev;
        void __iomem            *base;
        int                     irq[13];

        uint32_t                *buffer;
        struct iio_trigger      *trig;

        struct mutex            lock;

        struct completion       completion;

        /*
         * Touchscreen LRADC channels receives a private slot in the CTRL4
         * register, the slot #7. Therefore only 7 slots instead of 8 in the
         * CTRL4 register can be mapped to LRADC channels when using the
         * touchscreen.
         *
         * Furthermore, certain LRADC channels are shared between touchscreen
         * and/or touch-buttons and generic LRADC block. Therefore when using
         * either of these, these channels are not available for the regular
         * sampling. The shared channels are as follows:
         *
         * CH0 -- Touch button #0
         * CH1 -- Touch button #1
         * CH2 -- Touch screen XPUL
         * CH3 -- Touch screen YPLL
         * CH4 -- Touch screen XNUL
         * CH5 -- Touch screen YNLR
         * CH6 -- Touch screen WIPER (5-wire only)
         *
         * The bitfields below represents which parts of the LRADC block are
         * switched into special mode of operation. These channels can not
         * be sampled as regular LRADC channels. The driver will refuse any
         * attempt to sample these channels.
         */
#define CHAN_MASK_TOUCHBUTTON           (0x3 << 0)
#define CHAN_MASK_TOUCHSCREEN_4WIRE     (0xf << 2)
#define CHAN_MASK_TOUCHSCREEN_5WIRE     (0x1f << 2)
        enum mxs_lradc_ts       use_touchscreen;
        bool                    stop_touchscreen;
        bool                    use_touchbutton;

        struct input_dev        *ts_input;
        struct work_struct      ts_work;
};

#define LRADC_CTRL0                             0x00
#define LRADC_CTRL0_TOUCH_DETECT_ENABLE         (1 << 23)
#define LRADC_CTRL0_TOUCH_SCREEN_TYPE           (1 << 22)
#define LRADC_CTRL0_YNNSW       /* YM */        (1 << 21)
#define LRADC_CTRL0_YPNSW       /* YP */        (1 << 20)
#define LRADC_CTRL0_YPPSW       /* YP */        (1 << 19)
#define LRADC_CTRL0_XNNSW       /* XM */        (1 << 18)
#define LRADC_CTRL0_XNPSW       /* XM */        (1 << 17)
#define LRADC_CTRL0_XPPSW       /* XP */        (1 << 16)
#define LRADC_CTRL0_PLATE_MASK                  (0x3f << 16)

#define LRADC_CTRL1                             0x10
#define LRADC_CTRL1_TOUCH_DETECT_IRQ_EN         (1 << 24)
#define LRADC_CTRL1_LRADC_IRQ_EN(n)             (1 << ((n) + 16))
#define LRADC_CTRL1_LRADC_IRQ_EN_MASK           (0x1fff << 16)
#define LRADC_CTRL1_LRADC_IRQ_EN_OFFSET         16
#define LRADC_CTRL1_TOUCH_DETECT_IRQ            (1 << 8)
#define LRADC_CTRL1_LRADC_IRQ(n)                (1 << (n))
#define LRADC_CTRL1_LRADC_IRQ_MASK              0x1fff
#define LRADC_CTRL1_LRADC_IRQ_OFFSET            0

#define LRADC_CTRL2                             0x20
#define LRADC_CTRL2_TEMPSENSE_PWD               (1 << 15)

#define LRADC_STATUS                            0x40
#define LRADC_STATUS_TOUCH_DETECT_RAW           (1 << 0)

#define LRADC_CH(n)                             (0x50 + (0x10 * (n)))
#define LRADC_CH_ACCUMULATE                     (1 << 29)
#define LRADC_CH_NUM_SAMPLES_MASK               (0x1f << 24)
#define LRADC_CH_NUM_SAMPLES_OFFSET             24
#define LRADC_CH_VALUE_MASK                     0x3ffff
#define LRADC_CH_VALUE_OFFSET                   0

#define LRADC_DELAY(n)                          (0xd0 + (0x10 * (n)))
#define LRADC_DELAY_TRIGGER_LRADCS_MASK         (0xff << 24)
#define LRADC_DELAY_TRIGGER_LRADCS_OFFSET       24
#define LRADC_DELAY_KICK                        (1 << 20)
#define LRADC_DELAY_TRIGGER_DELAYS_MASK         (0xf << 16)
#define LRADC_DELAY_TRIGGER_DELAYS_OFFSET       16
#define LRADC_DELAY_LOOP_COUNT_MASK             (0x1f << 11)
#define LRADC_DELAY_LOOP_COUNT_OFFSET           11
#define LRADC_DELAY_DELAY_MASK                  0x7ff
#define LRADC_DELAY_DELAY_OFFSET                0

#define LRADC_CTRL4                             0x140
#define LRADC_CTRL4_LRADCSELECT_MASK(n)         (0xf << ((n) * 4))
#define LRADC_CTRL4_LRADCSELECT_OFFSET(n)       ((n) * 4)

/*
 * Raw I/O operations
 */
static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
                        const struct iio_chan_spec *chan,
                        int *val, int *val2, long m)
{
        struct mxs_lradc *lradc = iio_priv(iio_dev);
        int ret;
        unsigned long mask;

        if (m != IIO_CHAN_INFO_RAW)
                return -EINVAL;

        /* Check for invalid channel */
        if (chan->channel > LRADC_MAX_TOTAL_CHANS)
                return -EINVAL;

        /* Validate the channel if it doesn't intersect with reserved chans. */
        bitmap_set(&mask, chan->channel, 1);
        ret = iio_validate_scan_mask_onehot(iio_dev, &mask);
        if (ret)
                return -EINVAL;

        /*
         * See if there is no buffered operation in progess. If there is, simply
         * bail out. This can be improved to support both buffered and raw IO at
         * the same time, yet the code becomes horribly complicated. Therefore I
         * applied KISS principle here.
         */
        ret = mutex_trylock(&lradc->lock);
        if (!ret)
                return -EBUSY;

        INIT_COMPLETION(lradc->completion);

        /*
         * No buffered operation in progress, map the channel and trigger it.
         * Virtual channel 0 is always used here as the others are always not
         * used if doing raw sampling.
         */
        writel(LRADC_CTRL1_LRADC_IRQ_EN_MASK,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);
        writel(0xff, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);

        /* Clean the slot's previous content, then set new one. */
        writel(LRADC_CTRL4_LRADCSELECT_MASK(0),
                lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_CLR);
        writel(chan->channel, lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_SET);

        writel(0, lradc->base + LRADC_CH(0));

        /* Enable the IRQ and start sampling the channel. */
        writel(LRADC_CTRL1_LRADC_IRQ_EN(0),
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_SET);
        writel(1 << 0, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_SET);

        /* Wait for completion on the channel, 1 second max. */
        ret = wait_for_completion_killable_timeout(&lradc->completion, HZ);
        if (!ret)
                ret = -ETIMEDOUT;
        if (ret < 0)
                goto err;

        /* Read the data. */
        *val = readl(lradc->base + LRADC_CH(0)) & LRADC_CH_VALUE_MASK;
        ret = IIO_VAL_INT;

err:
        writel(LRADC_CTRL1_LRADC_IRQ_EN(0),
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);

        mutex_unlock(&lradc->lock);

        return ret;
}

static const struct iio_info mxs_lradc_iio_info = {
        .driver_module          = THIS_MODULE,
        .read_raw               = mxs_lradc_read_raw,
};

/*
 * Touchscreen handling
 */
enum lradc_ts_plate {
        LRADC_SAMPLE_X,
        LRADC_SAMPLE_Y,
        LRADC_SAMPLE_PRESSURE,
};

static int mxs_lradc_ts_touched(struct mxs_lradc *lradc)
{
        uint32_t reg;

        /* Enable touch detection. */
        writel(LRADC_CTRL0_PLATE_MASK,
                lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);
        writel(LRADC_CTRL0_TOUCH_DETECT_ENABLE,
                lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_SET);

        msleep(LRADC_TS_SAMPLE_DELAY_MS);

        reg = readl(lradc->base + LRADC_STATUS);

        return reg & LRADC_STATUS_TOUCH_DETECT_RAW;
}

static int32_t mxs_lradc_ts_sample(struct mxs_lradc *lradc,
                                enum lradc_ts_plate plate, int change)
{
        unsigned long delay, jiff;
        uint32_t reg, ctrl0 = 0, chan = 0;
        /* The touchscreen always uses CTRL4 slot #7. */
        const uint8_t slot = 7;
        uint32_t val;

        /*
         * There are three correct configurations of the controller sampling
         * the touchscreen, each of these configuration provides different
         * information from the touchscreen.
         *
         * The following table describes the sampling configurations:
         * +-------------+-------+-------+-------+
         * | Wire \ Axis |   X   |   Y   |   Z   |
         * +---------------------+-------+-------+
         * |   X+ (CH2)  |   HI  |   TS  |   TS  |
         * +-------------+-------+-------+-------+
         * |   X- (CH4)  |   LO  |   SH  |   HI  |
         * +-------------+-------+-------+-------+
         * |   Y+ (CH3)  |   SH  |   HI  |   HI  |
         * +-------------+-------+-------+-------+
         * |   Y- (CH5)  |   TS  |   LO  |   SH  |
         * +-------------+-------+-------+-------+
         *
         * HI ... strong '1'  ; LO ... strong '0'
         * SH ... sample here ; TS ... tri-state
         *
         * There are a few other ways of obtaining the Z coordinate
         * (aka. pressure), but the one in the table seems to be the
         * most reliable one.
         */
        switch (plate) {
        case LRADC_SAMPLE_X:
                ctrl0 = LRADC_CTRL0_XPPSW | LRADC_CTRL0_XNNSW;
                chan = 3;
                break;
        case LRADC_SAMPLE_Y:
                ctrl0 = LRADC_CTRL0_YPPSW | LRADC_CTRL0_YNNSW;
                chan = 4;
                break;
        case LRADC_SAMPLE_PRESSURE:
                ctrl0 = LRADC_CTRL0_YPPSW | LRADC_CTRL0_XNNSW;
                chan = 5;
                break;
        }

        if (change) {
                writel(LRADC_CTRL0_PLATE_MASK,
                        lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);
                writel(ctrl0, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_SET);

                writel(LRADC_CTRL4_LRADCSELECT_MASK(slot),
                        lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_CLR);
                writel(chan << LRADC_CTRL4_LRADCSELECT_OFFSET(slot),
                        lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_SET);
        }

        writel(0xffffffff, lradc->base + LRADC_CH(slot) + STMP_OFFSET_REG_CLR);
        writel(1 << slot, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_SET);

        delay = jiffies + msecs_to_jiffies(LRADC_TS_SAMPLE_DELAY_MS);
        do {
                jiff = jiffies;
                reg = readl_relaxed(lradc->base + LRADC_CTRL1);
                if (reg & LRADC_CTRL1_LRADC_IRQ(slot))
                        break;
        } while (time_before(jiff, delay));

        writel(LRADC_CTRL1_LRADC_IRQ(slot),
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);

        if (time_after_eq(jiff, delay))
                return -ETIMEDOUT;

        val = readl(lradc->base + LRADC_CH(slot));
        val &= LRADC_CH_VALUE_MASK;

        return val;
}

static int32_t mxs_lradc_ts_sample_filter(struct mxs_lradc *lradc,
                                enum lradc_ts_plate plate)
{
        int32_t val, tot = 0;
        int i;

        val = mxs_lradc_ts_sample(lradc, plate, 1);

        /* Delay a bit so the touchscreen is stable. */
        mdelay(2);

        for (i = 0; i < LRADC_TS_SAMPLE_AMOUNT; i++) {
                val = mxs_lradc_ts_sample(lradc, plate, 0);
                tot += val;
        }

        return tot / LRADC_TS_SAMPLE_AMOUNT;
}

static void mxs_lradc_ts_work(struct work_struct *ts_work)
{
        struct mxs_lradc *lradc = container_of(ts_work,
                                struct mxs_lradc, ts_work);
        int val_x, val_y, val_p;
        bool valid = false;

        while (mxs_lradc_ts_touched(lradc)) {
                /* Disable touch detector so we can sample the touchscreen. */
                writel(LRADC_CTRL0_TOUCH_DETECT_ENABLE,
                        lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);

                if (likely(valid)) {
                        input_report_abs(lradc->ts_input, ABS_X, val_x);
                        input_report_abs(lradc->ts_input, ABS_Y, val_y);
                        input_report_abs(lradc->ts_input, ABS_PRESSURE, val_p);
                        input_report_key(lradc->ts_input, BTN_TOUCH, 1);
                        input_sync(lradc->ts_input);
                }

                valid = false;

                val_x = mxs_lradc_ts_sample_filter(lradc, LRADC_SAMPLE_X);
                if (val_x < 0)
                        continue;
                val_y = mxs_lradc_ts_sample_filter(lradc, LRADC_SAMPLE_Y);
                if (val_y < 0)
                        continue;
                val_p = mxs_lradc_ts_sample_filter(lradc, LRADC_SAMPLE_PRESSURE);
                if (val_p < 0)
                        continue;

                valid = true;
        }

        input_report_abs(lradc->ts_input, ABS_PRESSURE, 0);
        input_report_key(lradc->ts_input, BTN_TOUCH, 0);
        input_sync(lradc->ts_input);

        /* Do not restart the TS IRQ if the driver is shutting down. */
        if (lradc->stop_touchscreen)
                return;

        /* Restart the touchscreen interrupts. */
        writel(LRADC_CTRL1_TOUCH_DETECT_IRQ,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);
        writel(LRADC_CTRL1_TOUCH_DETECT_IRQ_EN,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_SET);
}

static int mxs_lradc_ts_open(struct input_dev *dev)
{
        struct mxs_lradc *lradc = input_get_drvdata(dev);

        /* The touchscreen is starting. */
        lradc->stop_touchscreen = false;

        /* Enable the touch-detect circuitry. */
        writel(LRADC_CTRL0_TOUCH_DETECT_ENABLE,
                lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_SET);

        /* Enable the touch-detect IRQ. */
        writel(LRADC_CTRL1_TOUCH_DETECT_IRQ_EN,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_SET);

        return 0;
}

static void mxs_lradc_ts_close(struct input_dev *dev)
{
        struct mxs_lradc *lradc = input_get_drvdata(dev);

        /* Indicate the touchscreen is stopping. */
        lradc->stop_touchscreen = true;
        mb();

        /* Wait until touchscreen thread finishes any possible remnants. */
        cancel_work_sync(&lradc->ts_work);

        /* Disable touchscreen touch-detect IRQ. */
        writel(LRADC_CTRL1_TOUCH_DETECT_IRQ_EN,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);

        /* Power-down touchscreen touch-detect circuitry. */
        writel(LRADC_CTRL0_TOUCH_DETECT_ENABLE,
                lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);
}

static int mxs_lradc_ts_register(struct mxs_lradc *lradc)
{
        struct input_dev *input;
        struct device *dev = lradc->dev;
        int ret;

        if (!lradc->use_touchscreen)
                return 0;

        input = input_allocate_device();
        if (!input) {
                dev_err(dev, "Failed to allocate TS device!\n");
                return -ENOMEM;
        }

        input->name = DRIVER_NAME;
        input->id.bustype = BUS_HOST;
        input->dev.parent = dev;
        input->open = mxs_lradc_ts_open;
        input->close = mxs_lradc_ts_close;

        __set_bit(EV_ABS, input->evbit);
        __set_bit(EV_KEY, input->evbit);
        __set_bit(BTN_TOUCH, input->keybit);
        input_set_abs_params(input, ABS_X, 0, LRADC_CH_VALUE_MASK, 0, 0);
        input_set_abs_params(input, ABS_Y, 0, LRADC_CH_VALUE_MASK, 0, 0);
        input_set_abs_params(input, ABS_PRESSURE, 0, LRADC_CH_VALUE_MASK, 0, 0);

        lradc->ts_input = input;
        input_set_drvdata(input, lradc);
        ret = input_register_device(input);
        if (ret)
                input_free_device(lradc->ts_input);

        return ret;
}

static void mxs_lradc_ts_unregister(struct mxs_lradc *lradc)
{
        if (!lradc->use_touchscreen)
                return;

        cancel_work_sync(&lradc->ts_work);

        input_unregister_device(lradc->ts_input);
}

/*
 * IRQ Handling
 */
static irqreturn_t mxs_lradc_handle_irq(int irq, void *data)
{
        struct iio_dev *iio = data;
        struct mxs_lradc *lradc = iio_priv(iio);
        unsigned long reg = readl(lradc->base + LRADC_CTRL1);
        const uint32_t ts_irq_mask =
                LRADC_CTRL1_TOUCH_DETECT_IRQ_EN |
                LRADC_CTRL1_TOUCH_DETECT_IRQ;

        if (!(reg & LRADC_CTRL1_LRADC_IRQ_MASK))
                return IRQ_NONE;

        /*
         * Touchscreen IRQ handling code has priority and therefore
         * is placed here. In case touchscreen IRQ arrives, disable
         * it ASAP
         */
        if (reg & LRADC_CTRL1_TOUCH_DETECT_IRQ) {
                writel(ts_irq_mask,
                        lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);
                if (!lradc->stop_touchscreen)
                        schedule_work(&lradc->ts_work);
        }

        if (iio_buffer_enabled(iio))
                iio_trigger_poll(iio->trig, iio_get_time_ns());
        else if (reg & LRADC_CTRL1_LRADC_IRQ(0))
                complete(&lradc->completion);

        writel(reg & LRADC_CTRL1_LRADC_IRQ_MASK,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);

        return IRQ_HANDLED;
}

/*
 * Trigger handling
 */
static irqreturn_t mxs_lradc_trigger_handler(int irq, void *p)
{
        struct iio_poll_func *pf = p;
        struct iio_dev *iio = pf->indio_dev;
        struct mxs_lradc *lradc = iio_priv(iio);
        const uint32_t chan_value = LRADC_CH_ACCUMULATE |
                ((LRADC_DELAY_TIMER_LOOP - 1) << LRADC_CH_NUM_SAMPLES_OFFSET);
        unsigned int i, j = 0;

        for_each_set_bit(i, iio->active_scan_mask, iio->masklength) {
                lradc->buffer[j] = readl(lradc->base + LRADC_CH(j));
                writel(chan_value, lradc->base + LRADC_CH(j));
                lradc->buffer[j] &= LRADC_CH_VALUE_MASK;
                lradc->buffer[j] /= LRADC_DELAY_TIMER_LOOP;
                j++;
        }

        if (iio->scan_timestamp) {
                s64 *timestamp = (s64 *)((u8 *)lradc->buffer +
                                        ALIGN(j, sizeof(s64)));
                *timestamp = pf->timestamp;
        }

        iio_push_to_buffers(iio, (u8 *)lradc->buffer);

        iio_trigger_notify_done(iio->trig);

        return IRQ_HANDLED;
}

static int mxs_lradc_configure_trigger(struct iio_trigger *trig, bool state)
{
        struct iio_dev *iio = trig->private_data;
        struct mxs_lradc *lradc = iio_priv(iio);
        const uint32_t st = state ? STMP_OFFSET_REG_SET : STMP_OFFSET_REG_CLR;

        writel(LRADC_DELAY_KICK, lradc->base + LRADC_DELAY(0) + st);

        return 0;
}

static const struct iio_trigger_ops mxs_lradc_trigger_ops = {
        .owner = THIS_MODULE,
        .set_trigger_state = &mxs_lradc_configure_trigger,
};

static int mxs_lradc_trigger_init(struct iio_dev *iio)
{
        int ret;
        struct iio_trigger *trig;

        trig = iio_trigger_alloc("%s-dev%i", iio->name, iio->id);
        if (trig == NULL)
                return -ENOMEM;

        trig->dev.parent = iio->dev.parent;
        trig->private_data = iio;
        trig->ops = &mxs_lradc_trigger_ops;

        ret = iio_trigger_register(trig);
        if (ret) {
                iio_trigger_free(trig);
                return ret;
        }

        iio->trig = trig;

        return 0;
}

static void mxs_lradc_trigger_remove(struct iio_dev *iio)
{
        iio_trigger_unregister(iio->trig);
        iio_trigger_free(iio->trig);
}

static int mxs_lradc_buffer_preenable(struct iio_dev *iio)
{
        struct mxs_lradc *lradc = iio_priv(iio);
        struct iio_buffer *buffer = iio->buffer;
        int ret = 0, chan, ofs = 0;
        unsigned long enable = 0;
        uint32_t ctrl4_set = 0;
        uint32_t ctrl4_clr = 0;
        uint32_t ctrl1_irq = 0;
        const uint32_t chan_value = LRADC_CH_ACCUMULATE |
                ((LRADC_DELAY_TIMER_LOOP - 1) << LRADC_CH_NUM_SAMPLES_OFFSET);
        const int len = bitmap_weight(buffer->scan_mask, LRADC_MAX_TOTAL_CHANS);

        if (!len)
                return -EINVAL;

        /*
         * Lock the driver so raw access can not be done during buffered
         * operation. This simplifies the code a lot.
         */
        ret = mutex_trylock(&lradc->lock);
        if (!ret)
                return -EBUSY;

        lradc->buffer = kmalloc(len * sizeof(*lradc->buffer), GFP_KERNEL);
        if (!lradc->buffer) {
                ret = -ENOMEM;
                goto err_mem;
        }

        ret = iio_sw_buffer_preenable(iio);
        if (ret < 0)
                goto err_buf;

        writel(LRADC_CTRL1_LRADC_IRQ_EN_MASK,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);
        writel(0xff, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);

        for_each_set_bit(chan, buffer->scan_mask, LRADC_MAX_TOTAL_CHANS) {
                ctrl4_set |= chan << LRADC_CTRL4_LRADCSELECT_OFFSET(ofs);
                ctrl4_clr |= LRADC_CTRL4_LRADCSELECT_MASK(ofs);
                ctrl1_irq |= LRADC_CTRL1_LRADC_IRQ_EN(ofs);
                writel(chan_value, lradc->base + LRADC_CH(ofs));
                bitmap_set(&enable, ofs, 1);
                ofs++;
        }

        writel(LRADC_DELAY_TRIGGER_LRADCS_MASK | LRADC_DELAY_KICK,
                lradc->base + LRADC_DELAY(0) + STMP_OFFSET_REG_CLR);

        writel(ctrl4_clr, lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_CLR);
        writel(ctrl4_set, lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_SET);

        writel(ctrl1_irq, lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_SET);

        writel(enable << LRADC_DELAY_TRIGGER_LRADCS_OFFSET,
                lradc->base + LRADC_DELAY(0) + STMP_OFFSET_REG_SET);

        return 0;

err_buf:
        kfree(lradc->buffer);
err_mem:
        mutex_unlock(&lradc->lock);
        return ret;
}

static int mxs_lradc_buffer_postdisable(struct iio_dev *iio)
{
        struct mxs_lradc *lradc = iio_priv(iio);

        writel(LRADC_DELAY_TRIGGER_LRADCS_MASK | LRADC_DELAY_KICK,
                lradc->base + LRADC_DELAY(0) + STMP_OFFSET_REG_CLR);

        writel(0xff, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);
        writel(LRADC_CTRL1_LRADC_IRQ_EN_MASK,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);

        kfree(lradc->buffer);
        mutex_unlock(&lradc->lock);

        return 0;
}

static bool mxs_lradc_validate_scan_mask(struct iio_dev *iio,
                                        const unsigned long *mask)
{
        struct mxs_lradc *lradc = iio_priv(iio);
        const int len = iio->masklength;
        const int map_chans = bitmap_weight(mask, len);
        int rsvd_chans = 0;
        unsigned long rsvd_mask = 0;

        if (lradc->use_touchbutton)
                rsvd_mask |= CHAN_MASK_TOUCHBUTTON;
        if (lradc->use_touchscreen == MXS_LRADC_TOUCHSCREEN_4WIRE)
                rsvd_mask |= CHAN_MASK_TOUCHSCREEN_4WIRE;
        if (lradc->use_touchscreen == MXS_LRADC_TOUCHSCREEN_5WIRE)
                rsvd_mask |= CHAN_MASK_TOUCHSCREEN_5WIRE;

        if (lradc->use_touchbutton)
                rsvd_chans++;
        if (lradc->use_touchscreen)
                rsvd_chans++;

        /* Test for attempts to map channels with special mode of operation. */
        if (bitmap_intersects(mask, &rsvd_mask, len))
                return false;

        /* Test for attempts to map more channels then available slots. */
        if (map_chans + rsvd_chans > LRADC_MAX_MAPPED_CHANS)
                return false;

        return true;
}

static const struct iio_buffer_setup_ops mxs_lradc_buffer_ops = {
        .preenable = &mxs_lradc_buffer_preenable,
        .postenable = &iio_triggered_buffer_postenable,
        .predisable = &iio_triggered_buffer_predisable,
        .postdisable = &mxs_lradc_buffer_postdisable,
        .validate_scan_mask = &mxs_lradc_validate_scan_mask,
};

/*
 * Driver initialization
 */

#define MXS_ADC_CHAN(idx, chan_type) {                          \
        .type = (chan_type),                                    \
        .indexed = 1,                                           \
        .scan_index = (idx),                                    \
        .info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT,            \
        .channel = (idx),                                       \
        .scan_type = {                                          \
                .sign = 'u',                                    \
                .realbits = 18,                                 \
                .storagebits = 32,                              \
        },                                                      \
}

static const struct iio_chan_spec mxs_lradc_chan_spec[] = {
        MXS_ADC_CHAN(0, IIO_VOLTAGE),
        MXS_ADC_CHAN(1, IIO_VOLTAGE),
        MXS_ADC_CHAN(2, IIO_VOLTAGE),
        MXS_ADC_CHAN(3, IIO_VOLTAGE),
        MXS_ADC_CHAN(4, IIO_VOLTAGE),
        MXS_ADC_CHAN(5, IIO_VOLTAGE),
        MXS_ADC_CHAN(6, IIO_VOLTAGE),
        MXS_ADC_CHAN(7, IIO_VOLTAGE),   /* VBATT */
        MXS_ADC_CHAN(8, IIO_TEMP),      /* Temp sense 0 */
        MXS_ADC_CHAN(9, IIO_TEMP),      /* Temp sense 1 */
        MXS_ADC_CHAN(10, IIO_VOLTAGE),  /* VDDIO */
        MXS_ADC_CHAN(11, IIO_VOLTAGE),  /* VTH */
        MXS_ADC_CHAN(12, IIO_VOLTAGE),  /* VDDA */
        MXS_ADC_CHAN(13, IIO_VOLTAGE),  /* VDDD */
        MXS_ADC_CHAN(14, IIO_VOLTAGE),  /* VBG */
        MXS_ADC_CHAN(15, IIO_VOLTAGE),  /* VDD5V */
};

static void mxs_lradc_hw_init(struct mxs_lradc *lradc)
{
        /* The ADC always uses DELAY CHANNEL 0. */
        const uint32_t adc_cfg =
                (1 << (LRADC_DELAY_TRIGGER_DELAYS_OFFSET + 0)) |
                (LRADC_DELAY_TIMER_PER << LRADC_DELAY_DELAY_OFFSET);

        stmp_reset_block(lradc->base);

        /* Configure DELAY CHANNEL 0 for generic ADC sampling. */
        writel(adc_cfg, lradc->base + LRADC_DELAY(0));

        /* Disable remaining DELAY CHANNELs */
        writel(0, lradc->base + LRADC_DELAY(1));
        writel(0, lradc->base + LRADC_DELAY(2));
        writel(0, lradc->base + LRADC_DELAY(3));

        /* Configure the touchscreen type */
        writel(LRADC_CTRL0_TOUCH_SCREEN_TYPE,
                lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);

        if (lradc->use_touchscreen == MXS_LRADC_TOUCHSCREEN_5WIRE) {
                writel(LRADC_CTRL0_TOUCH_SCREEN_TYPE,
                        lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_SET);
        }

        /* Start internal temperature sensing. */
        writel(0, lradc->base + LRADC_CTRL2);
}

static void mxs_lradc_hw_stop(struct mxs_lradc *lradc)
{
        int i;

        writel(LRADC_CTRL1_LRADC_IRQ_EN_MASK,
                lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);

        for (i = 0; i < LRADC_MAX_DELAY_CHANS; i++)
                writel(0, lradc->base + LRADC_DELAY(i));
}

static const struct of_device_id mxs_lradc_dt_ids[] = {
        { .compatible = "fsl,imx23-lradc", .data = (void *)IMX23_LRADC, },
        { .compatible = "fsl,imx28-lradc", .data = (void *)IMX28_LRADC, },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, mxs_lradc_dt_ids);

static int mxs_lradc_probe(struct platform_device *pdev)
{
        const struct of_device_id *of_id =
                of_match_device(mxs_lradc_dt_ids, &pdev->dev);
        const struct mxs_lradc_of_config *of_cfg =
                &mxs_lradc_of_config[(enum mxs_lradc_id)of_id->data];
        struct device *dev = &pdev->dev;
        struct device_node *node = dev->of_node;
        struct mxs_lradc *lradc;
        struct iio_dev *iio;
        struct resource *iores;
        uint32_t ts_wires = 0;
        int ret = 0;
        int i;

        /* Allocate the IIO device. */
        iio = iio_device_alloc(sizeof(*lradc));
        if (!iio) {
                dev_err(dev, "Failed to allocate IIO device\n");
                return -ENOMEM;
        }

        lradc = iio_priv(iio);

        /* Grab the memory area */
        iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        lradc->dev = &pdev->dev;
        lradc->base = devm_ioremap_resource(dev, iores);
        if (IS_ERR(lradc->base)) {
                ret = PTR_ERR(lradc->base);
                goto err_addr;
        }

        INIT_WORK(&lradc->ts_work, mxs_lradc_ts_work);

        /* Check if touchscreen is enabled in DT. */
        ret = of_property_read_u32(node, "fsl,lradc-touchscreen-wires",
                                &ts_wires);
        if (ret)
                dev_info(dev, "Touchscreen not enabled.\n");
        else if (ts_wires == 4)
                lradc->use_touchscreen = MXS_LRADC_TOUCHSCREEN_4WIRE;
        else if (ts_wires == 5)
                lradc->use_touchscreen = MXS_LRADC_TOUCHSCREEN_5WIRE;
        else
                dev_warn(dev, "Unsupported number of touchscreen wires (%d)\n",
                                ts_wires);

        /* Grab all IRQ sources */
        for (i = 0; i < of_cfg->irq_count; i++) {
                lradc->irq[i] = platform_get_irq(pdev, i);
                if (lradc->irq[i] < 0) {
                        ret = -EINVAL;
                        goto err_addr;
                }

                ret = devm_request_irq(dev, lradc->irq[i],
                                        mxs_lradc_handle_irq, 0,
                                        of_cfg->irq_name[i], iio);
                if (ret)
                        goto err_addr;
        }

        platform_set_drvdata(pdev, iio);

        init_completion(&lradc->completion);
        mutex_init(&lradc->lock);

        iio->name = pdev->name;
        iio->dev.parent = &pdev->dev;
        iio->info = &mxs_lradc_iio_info;
        iio->modes = INDIO_DIRECT_MODE;
        iio->channels = mxs_lradc_chan_spec;
        iio->num_channels = ARRAY_SIZE(mxs_lradc_chan_spec);

        ret = iio_triggered_buffer_setup(iio, &iio_pollfunc_store_time,
                                &mxs_lradc_trigger_handler,
                                &mxs_lradc_buffer_ops);
        if (ret)
                goto err_addr;

        ret = mxs_lradc_trigger_init(iio);
        if (ret)
                goto err_trig;

        /* Register the touchscreen input device. */
        ret = mxs_lradc_ts_register(lradc);
        if (ret)
                goto err_dev;

        /* Register IIO device. */
        ret = iio_device_register(iio);
        if (ret) {
                dev_err(dev, "Failed to register IIO device\n");
                goto err_ts;
        }

        /* Configure the hardware. */
        mxs_lradc_hw_init(lradc);

        return 0;

err_ts:
        mxs_lradc_ts_unregister(lradc);
err_dev:
        mxs_lradc_trigger_remove(iio);
err_trig:
        iio_triggered_buffer_cleanup(iio);
err_addr:
        iio_device_free(iio);
        return ret;
}

static int mxs_lradc_remove(struct platform_device *pdev)
{
        struct iio_dev *iio = platform_get_drvdata(pdev);
        struct mxs_lradc *lradc = iio_priv(iio);

        mxs_lradc_ts_unregister(lradc);

        mxs_lradc_hw_stop(lradc);

        iio_device_unregister(iio);
        iio_triggered_buffer_cleanup(iio);
        mxs_lradc_trigger_remove(iio);
        iio_device_free(iio);

        return 0;
}

static struct platform_driver mxs_lradc_driver = {
        .driver = {
                .name   = DRIVER_NAME,
                .owner  = THIS_MODULE,
                .of_match_table = mxs_lradc_dt_ids,
        },
        .probe  = mxs_lradc_probe,
        .remove = mxs_lradc_remove,
};

module_platform_driver(mxs_lradc_driver);

MODULE_AUTHOR("Marek Vasut <marex@denx.de>");
MODULE_DESCRIPTION("Freescale i.MX28 LRADC driver");
MODULE_LICENSE("GPL v2");