Subject: [PATCH 2/3 V2] iio: mxs: Implement support for touchscreen

From: [email-masked] (Jonathan Cameron)
Date: Thu, 27 Dec 2012 12:16:28 +0000

On 12/19/2012 05:01 PM, Marek Vasut wrote:
> Ccing Dmitry.
> 
> Also, Jonathan, can I get your review please?
Dratt caught me hiding from this one and hoping it would
go away ;)
> 
>> This patch implements support for sampling of a touchscreen into
>> the MXS LRADC driver. The LRADC block allows configuring some of
>> it's channels into special mode where they either output the drive
>> voltage or sample it, allowing it to operate a 4-wire or 5-wire
>> resistive touchscreen.
>>
>> In case the touchscreen mode is enabled, the LRADC slot #7 is
>> reserved for touchscreen only, therefore it is not possible to
>> sample 8 LRADC channels at time, but only 7 channels.
>>
>> The touchscreen controller is configured such that the PENDOWN event
>> disables touchscreen interrupts and triggers execution of worker
>> thread, which then polls the touchscreen controller for X, Y and
>> Pressure values. This reduces the overhead of interrupt-driven
>> operation. Upon the PENUP event, the worker thread re-enables the
>> PENDOWN detection interrupt and exits.
>>
>> Signed-off-by: Marek Vasut <[email-masked]>
>> Cc: Fabio Estevam <[email-masked]>
>> Cc: Jonathan Cameron <[email-masked]>
>> Cc: Shawn Guo <[email-masked]>
>> ---
>>  .../bindings/staging/iio/adc/mxs-lradc.txt         |    6 +
>>  drivers/staging/iio/adc/mxs-lradc.c                |  469
>> +++++++++++++++++++- 2 files changed, 454 insertions(+), 21 deletions(-)
>>
>> V2: - Replace the use_touchscreen* with enum mxs_lradc_ts, which now tracks
>>       touchscreen state (OFF, 4-wire, 5-wire)
>>     - Add "stop_touchscreen" bit, which indicates the touchscreen is going
>> down and makes the driver not re-enable touchscreen interrupts and start
>> any new touchscreen works.
>>     - Make all bitfields "unsigned int" instead of plain "int"
>>     - Use switch(plate) in mxs_lradc_ts_sample()
>>     - Cancel touchscreen thread in mxs_lradc_ts_close(), do this only after
>>       we are sure touchscreen interrupt is off and will never be
>> re-enabled. This avoids serious race condition.
>>     - Call input_free_device() if input_register_device() fails to avoid
>> memory leak.
>>     - Do not call input_free_device() after input_unregister_device() in
>>       mxs_lradc_ts_unregister() to avoid double-free
>>
>> diff --git
>> a/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt
>> b/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt index
>> 801d58c..4688205 100644
>> --- a/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt
>> +++ b/Documentation/devicetree/bindings/staging/iio/adc/mxs-lradc.txt
>> @@ -5,6 +5,12 @@ Required properties:
>>  - reg: Address and length of the register set for the device
>>  - interrupts: Should contain the LRADC interrupts
>>
>> +Optional properties:
>> +- fsl,lradc-touchscreen-wires: Number of wires used to connect the
>> touchscreen +                               to LRADC. Valid value is
>> either 4 or 5. If this +                               property is not
>> present, then the touchscreen is +                               disabled.
>> +
>>  Examples:
>>
>>  	lradc at 80050000 {
>> diff --git a/drivers/staging/iio/adc/mxs-lradc.c
>> b/drivers/staging/iio/adc/mxs-lradc.c index 6249957..52317ef 100644
>> --- a/drivers/staging/iio/adc/mxs-lradc.c
>> +++ b/drivers/staging/iio/adc/mxs-lradc.c
>> @@ -32,6 +32,8 @@
>>  #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>
>> @@ -59,6 +61,21 @@
>>  #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
>> +
>>  static const char * const mxs_lradc_irq_name[] = {
>>  	"mxs-lradc-touchscreen",
>>  	"mxs-lradc-thresh0",
>> @@ -75,6 +92,12 @@ static const char * const mxs_lradc_irq_name[] = {
>>  	"mxs-lradc-button1",
>>  };
>>
>> +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;
>> @@ -86,21 +109,69 @@ struct mxs_lradc {
>>  	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;
>> +	unsigned int		stop_touchscreen:1;
>> +	unsigned int		use_touchbutton:1;
>> +
>> +	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_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_LRADC_IRQ(n)		(1 << (n))
>> -#define	LRADC_CTRL1_LRADC_IRQ_MASK		0x1fff
>> +#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)
>> @@ -132,6 +203,7 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
>>  {
>>  	struct mxs_lradc *lradc = iio_priv(iio_dev);
>>  	int ret;
>> +	unsigned long mask;
>>
>>  	if (m != IIO_CHAN_INFO_RAW)
>>  		return -EINVAL;
>> @@ -140,6 +212,12 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
>>  	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
>> @@ -161,7 +239,11 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
>>  		lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);
>>  	writel(0xff, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);
>>
>> -	writel(chan->channel, lradc->base + LRADC_CTRL4);
>> +	/* 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. */
>> @@ -195,6 +277,272 @@ static const struct iio_info mxs_lradc_iio_info = {
>>  };
>>
>>  /*
>> + * 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 = 0;
>> +
>> +	/* 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 = 1;
>> +
>> +	/* 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);
>> +
>> +	/* Wait until touchscreen thread finishes any possible remnants. */
>> +	cancel_work_sync(&lradc->ts_work);
>> +}
>> +
>> +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_warn(dev, "Failed to allocate TS device, disabling.\n");
>> +		lradc->use_touchscreen = MXS_LRADC_TOUCHSCREEN_NONE;
>> +		return 0;
>> +	}
>> +
>> +	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;
>> +
>> +	if (!lradc->ts_input)
>> +		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)
>> @@ -202,14 +550,24 @@ 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 shall probably have priority
>> -	 * and therefore shall be placed here.
>> +	 * 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());
>> @@ -306,8 +664,10 @@ 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, enable = 0;
>> -	uint32_t ctrl4 = 0;
>> +	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);
>> @@ -339,17 +699,20 @@ static int mxs_lradc_buffer_preenable(struct iio_dev
>> *iio) writel(0xff, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);
>>
>>  	for_each_set_bit(chan, buffer->scan_mask, LRADC_MAX_TOTAL_CHANS) {
>> -		ctrl4 |= chan << LRADC_CTRL4_LRADCSELECT_OFFSET(ofs);
>> +		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));
>> -		enable |= 1 << 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, lradc->base + LRADC_CTRL4);
>> +	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,
>> @@ -384,9 +747,33 @@ static int mxs_lradc_buffer_postdisable(struct iio_dev
>> *iio) static bool mxs_lradc_validate_scan_mask(struct iio_dev *iio,
>>  					const unsigned long *mask)
>>  {
>> -	const int mw = bitmap_weight(mask, iio->masklength);
>> -
>> -	return mw <= LRADC_MAX_MAPPED_CHANS;
>> +	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 0;
>> +
>> +	/* Test for attempts to map more channels then available slots. */
>> +	if (map_chans + rsvd_chans > LRADC_MAX_MAPPED_CHANS)
>> +		return 0;
>> +
>> +	return 1;
>>  }
>>
>>  static const struct iio_buffer_setup_ops mxs_lradc_buffer_ops = {
>> @@ -435,15 +822,29 @@ static const struct iio_chan_spec
>> mxs_lradc_chan_spec[] = {
>>
>>  static void mxs_lradc_hw_init(struct mxs_lradc *lradc)
>>  {
>> -	int i;
>> -	const uint32_t cfg =
>> +	/* 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);
>>
>> -	for (i = 0; i < LRADC_MAX_DELAY_CHANS; i++)
>> -		writel(cfg | (1 << (LRADC_DELAY_TRIGGER_DELAYS_OFFSET + i)),
>> -			lradc->base + LRADC_DELAY(i));
>> +	/* 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);
>> @@ -463,9 +864,11 @@ static void mxs_lradc_hw_stop(struct mxs_lradc *lradc)
>>  static int __devinit mxs_lradc_probe(struct platform_device *pdev)
>>  {
>>  	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;
>>
>> @@ -487,6 +890,21 @@ static int __devinit mxs_lradc_probe(struct
>> platform_device *pdev) 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 < 13; i++) {
>>  		lradc->irq[i] = platform_get_irq(pdev, i);
>> @@ -524,11 +942,16 @@ static int __devinit mxs_lradc_probe(struct
>> platform_device *pdev) 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_dev;
>> +		goto err_ts;
>>  	}
>>
>>  	/* Configure the hardware. */
>> @@ -536,6 +959,8 @@ static int __devinit mxs_lradc_probe(struct
>> platform_device *pdev)
>>
>>  	return 0;
>>
>> +err_ts:
>> +	mxs_lradc_ts_unregister(lradc);
>>  err_dev:
>>  	mxs_lradc_trigger_remove(iio);
>>  err_trig:
>> @@ -550,6 +975,8 @@ static int __devexit 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);
> --
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