Subject: [PATCH 5/7] Staging/iio/adc/touchscreen/MXS: add interrupt driven touch detection

From: [email-masked] (Jonathan Cameron)
Date: Sat, 21 Sep 2013 13:36:33 +0100

On 09/19/13 13:22, Juergen Beisert wrote:
> For battery driven systems it is a very bad idea to collect the touchscreen
> data within a kernel busy loop.
> 
> This change uses the features of the hardware to delay and accumulate samples in
> hardware to avoid a high interrupt and CPU load.
> 
> Note: this is only tested on an i.MX23 SoC yet.
> 
> Signed-off-by: Juergen Beisert <[email-masked]>
> CC: linux-arm-kernel at lists.infradead.org
> CC: devel at driverdev.osuosl.org
> CC: Marek Vasut <[email-masked]>
> CC: Fabio Estevam <[email-masked]>
> CC: Jonathan Cameron <[email-masked]>

Please repost with Dmitry Torokhov and the linux input list cc'd.

Whilst this looks fine to me, it is definitely an input patch even if
the code resides in iio.

Also, I'm not going to take this series until we have confirmation from Marek
or someone else that we aren't introducing regressions into the i.MX23 support.

> ---
>  drivers/staging/iio/adc/mxs-lradc.c | 532 ++++++++++++++++++++++++++++++++----
>  1 file changed, 476 insertions(+), 56 deletions(-)
> 
> diff --git a/drivers/staging/iio/adc/mxs-lradc.c b/drivers/staging/iio/adc/mxs-lradc.c
> index c70c31f..9f3f367 100644
> --- a/drivers/staging/iio/adc/mxs-lradc.c
> +++ b/drivers/staging/iio/adc/mxs-lradc.c
> @@ -129,6 +129,17 @@ enum mxs_lradc_ts {
>  	MXS_LRADC_TOUCHSCREEN_5WIRE,
>  };
>  
> +/*
> + * Touchscreen handling
> + */
> +enum lradc_ts_plate {
> +	LRADC_TOUCH = 0,
> +	LRADC_SAMPLE_X,
> +	LRADC_SAMPLE_Y,
> +	LRADC_SAMPLE_PRESSURE,
> +	LRADC_SAMPLE_VALID,
> +};
> +
>  struct mxs_lradc {
>  	struct device		*dev;
>  	void __iomem		*base;
> @@ -169,13 +180,25 @@ struct mxs_lradc {
>  #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;
>  
>  	enum mxs_lradc_id	soc;
> +	enum lradc_ts_plate	cur_plate; /* statemachine */
> +	bool			ts_valid;
> +	unsigned		ts_x_pos;
> +	unsigned		ts_y_pos;
> +	unsigned		ts_pressure;
> +
> +	/* handle touchscreen's physical behaviour */
> +	/* samples per coordinate */
> +	unsigned		over_sample_cnt;
> +	/* time clocks between samples */
> +	unsigned		over_sample_delay;
> +	/* time in clocks to wait after the plates where switched */
> +	unsigned		settling_delay;
>  };
>  
>  #define	LRADC_CTRL0				0x00
> @@ -227,19 +250,33 @@ struct mxs_lradc {
>  #define	LRADC_CH_ACCUMULATE			(1 << 29)
>  #define	LRADC_CH_NUM_SAMPLES_MASK		(0x1f << 24)
>  #define	LRADC_CH_NUM_SAMPLES_OFFSET		24
> +#define	LRADC_CH_NUM_SAMPLES(x) \
> +				((x) << LRADC_CH_NUM_SAMPLES_OFFSET)
>  #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_TRIGGER(x) \
> +				(((x) << LRADC_DELAY_TRIGGER_LRADCS_OFFSET) & \
> +				LRADC_DELAY_TRIGGER_LRADCS_MASK)
>  #define	LRADC_DELAY_KICK			(1 << 20)
>  #define	LRADC_DELAY_TRIGGER_DELAYS_MASK		(0xf << 16)
>  #define	LRADC_DELAY_TRIGGER_DELAYS_OFFSET	16
> +#define	LRADC_DELAY_TRIGGER_DELAYS(x) \
> +				(((x) << LRADC_DELAY_TRIGGER_DELAYS_OFFSET) & \
> +				LRADC_DELAY_TRIGGER_DELAYS_MASK)
>  #define	LRADC_DELAY_LOOP_COUNT_MASK		(0x1f << 11)
>  #define	LRADC_DELAY_LOOP_COUNT_OFFSET		11
> +#define	LRADC_DELAY_LOOP(x) \
> +				(((x) << LRADC_DELAY_LOOP_COUNT_OFFSET) & \
> +				LRADC_DELAY_LOOP_COUNT_MASK)
>  #define	LRADC_DELAY_DELAY_MASK			0x7ff
>  #define	LRADC_DELAY_DELAY_OFFSET		0
> +#define	LRADC_DELAY_DELAY(x) \
> +				(((x) << LRADC_DELAY_DELAY_OFFSET) & \
> +				LRADC_DELAY_DELAY_MASK)
>  
>  #define	LRADC_CTRL4				0x140
>  #define	LRADC_CTRL4_LRADCSELECT_MASK(n)		(0xf << ((n) * 4))
> @@ -319,6 +356,404 @@ static u32 mxs_lradc_drive_pressure(struct mxs_lradc *lradc)
>  		return LRADC_CTRL0_MX28_YPPSW | LRADC_CTRL0_MX28_XNNSW;
>  }
>  
> +static bool mxs_lradc_check_touch_event(struct mxs_lradc *lradc)
> +{
> +	return !!(readl(lradc->base + LRADC_STATUS) &
> +					LRADC_STATUS_TOUCH_DETECT_RAW);
> +}
> +
> +static void mxs_lradc_setup_ts_channel(struct mxs_lradc *lradc, unsigned ch)
> +{
> +	/*
> +	 * prepare for oversampling conversion
> +	 *
> +	 * from the datasheet:
> +	 * "The ACCUMULATE bit in the appropriate channel register
> +	 * HW_LRADC_CHn must be set to 1 if NUM_SAMPLES is greater then 0;
> +	 * otherwise, the IRQs will not fire."
> +	 */
> +	mxs_lradc_reg_wrt(lradc, LRADC_CH_ACCUMULATE |
> +			LRADC_CH_NUM_SAMPLES(lradc->over_sample_cnt - 1),
> +			LRADC_CH(ch));
> +
> +	/* from the datasheet:
> +	 * "Software must clear this register in preparation for a
> +	 * multi-cycle accumulation.
> +	 */
> +	mxs_lradc_reg_clear(lradc, LRADC_CH_VALUE_MASK, LRADC_CH(ch));
> +
> +	/* prepare the delay/loop unit according to the oversampling count */
> +	mxs_lradc_reg_wrt(lradc, LRADC_DELAY_TRIGGER(1 << ch) |
> +		LRADC_DELAY_TRIGGER_DELAYS(0) |
> +		LRADC_DELAY_LOOP(lradc->over_sample_cnt - 1) |
> +		LRADC_DELAY_DELAY(lradc->over_sample_delay - 1),
> +			LRADC_DELAY(3));
> +
> +	mxs_lradc_reg_clear(lradc, LRADC_CTRL1_LRADC_IRQ(2) |
> +			LRADC_CTRL1_LRADC_IRQ(3) | LRADC_CTRL1_LRADC_IRQ(4) |
> +			LRADC_CTRL1_LRADC_IRQ(5), LRADC_CTRL1);
> +
> +	/* wake us again, when the complete conversion is done */
> +	mxs_lradc_reg_set(lradc, LRADC_CTRL1_LRADC_IRQ_EN(ch), LRADC_CTRL1);
> +	/*
> +	 * after changing the touchscreen plates setting
> +	 * the signals need some initial time to settle. Start the
> +	 * SoC's delay unit and start the conversion later
> +	 * and automatically.
> +	 */
> +	mxs_lradc_reg_wrt(lradc, LRADC_DELAY_TRIGGER(0) | /* don't trigger ADC */
> +		LRADC_DELAY_TRIGGER_DELAYS(1 << 3) | /* trigger DELAY unit#3 */
> +		LRADC_DELAY_KICK |
> +		LRADC_DELAY_DELAY(lradc->settling_delay),
> +			LRADC_DELAY(2));
> +}
> +
> +/*
> + * Pressure detection is special:
> + * We want to do both required measurements for the pressure detection in
> + * one turn. Use the hardware features to chain both conversions and let the
> + * hardware report one interrupt if both conversions are done
> + */
> +static void mxs_lradc_setup_ts_pressure(struct mxs_lradc *lradc, unsigned ch1,
> +							unsigned ch2)
> +{
> +	u32 reg;
> +
> +	/*
> +	 * prepare for oversampling conversion
> +	 *
> +	 * from the datasheet:
> +	 * "The ACCUMULATE bit in the appropriate channel register
> +	 * HW_LRADC_CHn must be set to 1 if NUM_SAMPLES is greater then 0;
> +	 * otherwise, the IRQs will not fire."
> +	 */
> +	reg = LRADC_CH_ACCUMULATE |
> +		LRADC_CH_NUM_SAMPLES(lradc->over_sample_cnt - 1);
> +	mxs_lradc_reg_wrt(lradc, reg, LRADC_CH(ch1));
> +	mxs_lradc_reg_wrt(lradc, reg, LRADC_CH(ch2));
> +
> +	/* from the datasheet:
> +	 * "Software must clear this register in preparation for a
> +	 * multi-cycle accumulation.
> +	 */
> +	mxs_lradc_reg_clear(lradc, LRADC_CH_VALUE_MASK, LRADC_CH(ch1));
> +	mxs_lradc_reg_clear(lradc, LRADC_CH_VALUE_MASK, LRADC_CH(ch2));
> +
> +	/* prepare the delay/loop unit according to the oversampling count */
> +	mxs_lradc_reg_wrt(lradc, LRADC_DELAY_TRIGGER(1 << ch1) |
> +		LRADC_DELAY_TRIGGER(1 << ch2) | /* start both channels */
> +		LRADC_DELAY_TRIGGER_DELAYS(0) |
> +		LRADC_DELAY_LOOP(lradc->over_sample_cnt - 1) |
> +		LRADC_DELAY_DELAY(lradc->over_sample_delay - 1),
> +					LRADC_DELAY(3));
> +
> +	mxs_lradc_reg_clear(lradc, LRADC_CTRL1_LRADC_IRQ(2) |
> +			LRADC_CTRL1_LRADC_IRQ(3) | LRADC_CTRL1_LRADC_IRQ(4) |
> +			LRADC_CTRL1_LRADC_IRQ(5), LRADC_CTRL1);
> +
> +	/* wake us again, when the conversions are done */
> +	mxs_lradc_reg_set(lradc, LRADC_CTRL1_LRADC_IRQ_EN(ch2), LRADC_CTRL1);
> +	/*
> +	 * after changing the touchscreen plates setting
> +	 * the signals need some initial time to settle. Start the
> +	 * SoC's delay unit and start the conversion later
> +	 * and automatically.
> +	 */
> +	mxs_lradc_reg_wrt(lradc, LRADC_DELAY_TRIGGER(0) | /* don't trigger ADC */
> +		LRADC_DELAY_TRIGGER_DELAYS(1 << 3) | /* trigger DELAY unit#3 */
> +		LRADC_DELAY_KICK |
> +		LRADC_DELAY_DELAY(lradc->settling_delay), LRADC_DELAY(2));
> +}
> +
> +static unsigned mxs_lradc_read_raw_channel(struct mxs_lradc *lradc,
> +							unsigned channel)
> +{
> +	u32 reg;
> +	unsigned num_samples, val;
> +
> +	reg = readl(lradc->base + LRADC_CH(channel));
> +	if (reg & LRADC_CH_ACCUMULATE)
> +		num_samples = lradc->over_sample_cnt;
> +	else
> +		num_samples = 1;
> +
> +	val = (reg & LRADC_CH_VALUE_MASK) >> LRADC_CH_VALUE_OFFSET;
> +	return val / num_samples;
> +}
> +
> +static unsigned mxs_lradc_read_ts_pressure(struct mxs_lradc *lradc,
> +						unsigned ch1, unsigned ch2)
> +{
> +	u32 reg, mask;
> +	unsigned pressure, m1, m2;
> +
> +	mask = LRADC_CTRL1_LRADC_IRQ(ch1) | LRADC_CTRL1_LRADC_IRQ(ch2);
> +	reg = readl(lradc->base + LRADC_CTRL1) & mask;
> +
> +	while (reg != mask) {
> +		reg = readl(lradc->base + LRADC_CTRL1) & mask;
> +		dev_dbg(lradc->dev, "One channel is still busy: %X\n", reg);
> +	}
> +
> +	m1 = mxs_lradc_read_raw_channel(lradc, ch1);
> +	m2 = mxs_lradc_read_raw_channel(lradc, ch2);
> +
> +	if (m2 == 0) {
> +		dev_warn(lradc->dev, "Cannot calculate pressure\n");
> +		return 1 << (LRADC_RESOLUTION - 1);
> +	}
> +
> +	/* simply scale the value from 0 ... max ADC resolution */
> +	pressure = m1;
> +	pressure *= (1 << LRADC_RESOLUTION);
> +	pressure /= m2;
> +
> +	dev_dbg(lradc->dev, "Pressure = %u\n", pressure);
> +	return pressure;
> +}
> +
> +#define TS_CH_XP 2
> +#define TS_CH_YP 3
> +#define TS_CH_XM 4
> +#define TS_CH_YM 5
> +
> +static int mxs_lradc_read_ts_channel(struct mxs_lradc *lradc)
> +{
> +	u32 reg;
> +	int val;
> +
> +	reg = readl(lradc->base + LRADC_CTRL1);
> +
> +	/* only channels 3 to 5 are of interest here */
> +	if (reg & LRADC_CTRL1_LRADC_IRQ(TS_CH_YP)) {
> +		mxs_lradc_reg_clear(lradc, LRADC_CTRL1_LRADC_IRQ_EN(TS_CH_YP) |
> +			LRADC_CTRL1_LRADC_IRQ(TS_CH_YP), LRADC_CTRL1);
> +		val = mxs_lradc_read_raw_channel(lradc, TS_CH_YP);
> +	} else if (reg & LRADC_CTRL1_LRADC_IRQ(TS_CH_XM)) {
> +		mxs_lradc_reg_clear(lradc, LRADC_CTRL1_LRADC_IRQ_EN(TS_CH_XM) |
> +			LRADC_CTRL1_LRADC_IRQ(TS_CH_XM), LRADC_CTRL1);
> +		val = mxs_lradc_read_raw_channel(lradc, TS_CH_XM);
> +	} else if (reg & LRADC_CTRL1_LRADC_IRQ(TS_CH_YM)) {
> +		mxs_lradc_reg_clear(lradc, LRADC_CTRL1_LRADC_IRQ_EN(TS_CH_YM) |
> +			LRADC_CTRL1_LRADC_IRQ(TS_CH_YM), LRADC_CTRL1);
> +		val = mxs_lradc_read_raw_channel(lradc, TS_CH_YM);
> +	} else {
> +		return -EIO;
> +	}
> +
> +	mxs_lradc_reg_wrt(lradc, 0, LRADC_DELAY(2));
> +	mxs_lradc_reg_wrt(lradc, 0, LRADC_DELAY(3));
> +
> +	return val;
> +}
> +
> +/*
> + * YP(open)--+-------------+
> + *           |             |--+
> + *           |             |  |
> + *    YM(-)--+-------------+  |
> + *             +--------------+
> + *             |              |
> + *         XP(weak+)        XM(open)
> + *
> + * "weak+" means 200k Ohm VDDIO
> + * (-) means GND
> + */
> +static void mxs_lradc_setup_touch_detection(struct mxs_lradc *lradc)
> +{
> +	/*
> +	 * In order to detect a touch event the 'touch detect enable' bit
> +	 * enables:
> +	 *  - a weak pullup to the X+ connector
> +	 *  - a strong ground at the Y- connector
> +	 */
> +	mxs_lradc_reg_clear(lradc, mxs_lradc_plate_mask(lradc), LRADC_CTRL0);
> +	mxs_lradc_reg_set(lradc, mxs_lradc_touch_detect_bit(lradc),
> +				LRADC_CTRL0);
> +}
> +
> +/*
> + * YP(meas)--+-------------+
> + *           |             |--+
> + *           |             |  |
> + * YM(open)--+-------------+  |
> + *             +--------------+
> + *             |              |
> + *           XP(+)          XM(-)
> + *
> + * (+) means here 1.85 V
> + * (-) means here GND
> + */
> +static void mxs_lradc_prepare_x_pos(struct mxs_lradc *lradc)
> +{
> +	mxs_lradc_reg_clear(lradc, mxs_lradc_plate_mask(lradc), LRADC_CTRL0);
> +	mxs_lradc_reg_set(lradc, mxs_lradc_drive_x_plate(lradc), LRADC_CTRL0);
> +
> +	lradc->cur_plate = LRADC_SAMPLE_X;
> +	mxs_lradc_setup_ts_channel(lradc, TS_CH_YP);
> +}
> +
> +/*
> + *   YP(+)--+-------------+
> + *          |             |--+
> + *          |             |  |
> + *   YM(-)--+-------------+  |
> + *            +--------------+
> + *            |              |
> + *         XP(open)        XM(meas)
> + *
> + * (+) means here 1.85 V
> + * (-) means here GND
> + */
> +static void mxs_lradc_prepare_y_pos(struct mxs_lradc *lradc)
> +{
> +	mxs_lradc_reg_clear(lradc, mxs_lradc_plate_mask(lradc), LRADC_CTRL0);
> +	mxs_lradc_reg_set(lradc, mxs_lradc_drive_y_plate(lradc), LRADC_CTRL0);
> +
> +	lradc->cur_plate = LRADC_SAMPLE_Y;
> +	mxs_lradc_setup_ts_channel(lradc, TS_CH_XM);
> +}
> +
> +/*
> + *    YP(+)--+-------------+
> + *           |             |--+
> + *           |             |  |
> + * YM(meas)--+-------------+  |
> + *             +--------------+
> + *             |              |
> + *          XP(meas)        XM(-)
> + *
> + * (+) means here 1.85 V
> + * (-) means here GND
> + */
> +static void mxs_lradc_prepare_pressure(struct mxs_lradc *lradc)
> +{
> +	mxs_lradc_reg_clear(lradc, mxs_lradc_plate_mask(lradc), LRADC_CTRL0);
> +	mxs_lradc_reg_set(lradc, mxs_lradc_drive_pressure(lradc), LRADC_CTRL0);
> +
> +	lradc->cur_plate = LRADC_SAMPLE_PRESSURE;
> +	mxs_lradc_setup_ts_pressure(lradc, TS_CH_XP, TS_CH_YM);
> +}
> +
> +static void mxs_lradc_enable_touch_detection(struct mxs_lradc *lradc)
> +{
> +	mxs_lradc_setup_touch_detection(lradc);
> +
> +	lradc->cur_plate = LRADC_TOUCH;
> +	mxs_lradc_reg_clear(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ |
> +				LRADC_CTRL1_TOUCH_DETECT_IRQ_EN, LRADC_CTRL1);
> +	mxs_lradc_reg_set(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ_EN, LRADC_CTRL1);
> +}
> +
> +static void mxs_lradc_report_ts_event(struct mxs_lradc *lradc)
> +{
> +	input_report_abs(lradc->ts_input, ABS_X, lradc->ts_x_pos);
> +	input_report_abs(lradc->ts_input, ABS_Y, lradc->ts_y_pos);
> +	input_report_abs(lradc->ts_input, ABS_PRESSURE, lradc->ts_pressure);
> +	input_report_key(lradc->ts_input, BTN_TOUCH, 1);
> +	input_sync(lradc->ts_input);
> +}
> +
> +static void mxs_lradc_complete_touch_event(struct mxs_lradc *lradc)
> +{
> +	mxs_lradc_setup_touch_detection(lradc);
> +	lradc->cur_plate = LRADC_SAMPLE_VALID;
> +	/*
> +	 * start a dummy conversion to burn time to settle the signals
> +	 * note: we are not interested in the conversion's value
> +	 */
> +	mxs_lradc_reg_wrt(lradc, 0, LRADC_CH(5));
> +	mxs_lradc_reg_clear(lradc, LRADC_CTRL1_LRADC_IRQ(5), LRADC_CTRL1);
> +	mxs_lradc_reg_set(lradc, LRADC_CTRL1_LRADC_IRQ_EN(5), LRADC_CTRL1);
> +	mxs_lradc_reg_wrt(lradc, LRADC_DELAY_TRIGGER(1 << 5) |
> +		LRADC_DELAY_KICK | LRADC_DELAY_DELAY(10), /* waste 5 ms */
> +			LRADC_DELAY(2));
> +}
> +
> +/*
> + * in order to avoid false measurements, report only samples where
> + * the surface is still touched after the position measurement
> + */
> +static void mxs_lradc_finish_touch_event(struct mxs_lradc *lradc, bool valid)
> +{
> +	/* if it is still touched, report the sample */
> +	if (valid && mxs_lradc_check_touch_event(lradc)) {
> +		lradc->ts_valid = true;
> +		mxs_lradc_report_ts_event(lradc);
> +	}
> +
> +	/* if it is even still touched, continue with the next measurement */
> +	if (mxs_lradc_check_touch_event(lradc)) {
> +		mxs_lradc_prepare_y_pos(lradc);
> +		return;
> +	}
> +
> +	if (lradc->ts_valid) {
> +		/* signal the release */
> +		lradc->ts_valid = false;
> +		input_report_key(lradc->ts_input, BTN_TOUCH, 0);
> +		input_sync(lradc->ts_input);
> +	}
> +
> +	/* if it is released, wait for the next touch via IRQ */
> +	mxs_lradc_reg_clear(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ, LRADC_CTRL1);
> +	mxs_lradc_reg_set(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ_EN, LRADC_CTRL1);
> +}
> +
> +/* touchscreen's state machine */
> +static void mxs_lradc_handle_touch(struct mxs_lradc *lradc)
> +{
> +	int val;
> +
> +	switch (lradc->cur_plate) {
> +	case LRADC_TOUCH:
> +		/*
> +		 * start with the Y-pos, because it uses nearly the same plate
> +		 * settings like the touch detection
> +		 */
> +		if (mxs_lradc_check_touch_event(lradc)) {
> +			mxs_lradc_reg_clear(lradc,
> +					LRADC_CTRL1_TOUCH_DETECT_IRQ_EN,
> +					LRADC_CTRL1);
> +			mxs_lradc_prepare_y_pos(lradc);
> +		}
> +		mxs_lradc_reg_clear(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ,
> +					LRADC_CTRL1);
> +		return;
> +
> +	case LRADC_SAMPLE_Y:
> +		val = mxs_lradc_read_ts_channel(lradc);
> +		if (val < 0) {
> +			mxs_lradc_enable_touch_detection(lradc); /* re-start */
> +			return;
> +		}
> +		lradc->ts_y_pos = val;
> +		mxs_lradc_prepare_x_pos(lradc);
> +		return;
> +
> +	case LRADC_SAMPLE_X:
> +		val = mxs_lradc_read_ts_channel(lradc);
> +		if (val < 0) {
> +			mxs_lradc_enable_touch_detection(lradc); /* re-start */
> +			return;
> +		}
> +		lradc->ts_x_pos = val;
> +		mxs_lradc_prepare_pressure(lradc);
> +		return;
> +
> +	case LRADC_SAMPLE_PRESSURE:
> +		lradc->ts_pressure =
> +			mxs_lradc_read_ts_pressure(lradc, TS_CH_XP, TS_CH_YM);
> +		mxs_lradc_complete_touch_event(lradc);
> +		return;
> +
> +	case LRADC_SAMPLE_VALID:
> +		val = mxs_lradc_read_ts_channel(lradc); /* ignore the value */
> +		mxs_lradc_finish_touch_event(lradc, 1);
> +		break;
> +	}
> +}
> +
>  /*
>   * Raw I/O operations
>   */
> @@ -392,15 +827,6 @@ static const struct iio_info mxs_lradc_iio_info = {
>  	.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;
> @@ -558,10 +984,6 @@ static void mxs_lradc_ts_work(struct work_struct *ts_work)
>  	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. */
>  	mxs_lradc_reg_clear(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ, LRADC_CTRL1);
>  	mxs_lradc_reg_set(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ_EN, LRADC_CTRL1);
> @@ -571,36 +993,29 @@ 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. */
> -	mxs_lradc_reg_set(lradc, mxs_lradc_touch_detect_bit(lradc),
> -						LRADC_CTRL0);
> -
> -	/* Enable the touch-detect IRQ. */
> -	mxs_lradc_reg_set(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ_EN, LRADC_CTRL1);
> +	mxs_lradc_enable_touch_detection(lradc);
>  
>  	return 0;
>  }
>  
> -static void mxs_lradc_ts_close(struct input_dev *dev)
> +static void mxs_lradc_disable_ts(struct mxs_lradc *lradc)
>  {
> -	struct mxs_lradc *lradc = input_get_drvdata(dev);
> -
> -	/* Indicate the touchscreen is stopping. */
> -	lradc->stop_touchscreen = true;
> -	mb();
> +	/* stop all interrupts from firing */
> +	mxs_lradc_reg_clear(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ_EN |
> +		LRADC_CTRL1_LRADC_IRQ_EN(2) | LRADC_CTRL1_LRADC_IRQ_EN(3) |
> +		LRADC_CTRL1_LRADC_IRQ_EN(4) | LRADC_CTRL1_LRADC_IRQ_EN(5),
> +		LRADC_CTRL1);
>  
> -	/* Wait until touchscreen thread finishes any possible remnants. */
> -	cancel_work_sync(&lradc->ts_work);
> +	/* Power-down touchscreen touch-detect circuitry. */
> +	mxs_lradc_reg_clear(lradc, mxs_lradc_plate_mask(lradc), LRADC_CTRL0);
> +}
>  
> -	/* Disable touchscreen touch-detect IRQ. */
> -	mxs_lradc_reg_clear(lradc, LRADC_CTRL1_TOUCH_DETECT_IRQ_EN,
> -						LRADC_CTRL1);
> +static void mxs_lradc_ts_close(struct input_dev *dev)
> +{
> +	struct mxs_lradc *lradc = input_get_drvdata(dev);
>  
> -	/* Power-down touchscreen touch-detect circuitry. */
> -	mxs_lradc_reg_clear(lradc, mxs_lradc_touch_detect_bit(lradc), LRADC_CTRL0);
> +	mxs_lradc_disable_ts(lradc);
>  }
>  
>  static int mxs_lradc_ts_register(struct mxs_lradc *lradc)
> @@ -646,8 +1061,7 @@ static void mxs_lradc_ts_unregister(struct mxs_lradc *lradc)
>  	if (!lradc->use_touchscreen)
>  		return;
>  
> -	cancel_work_sync(&lradc->ts_work);
> -
> +	mxs_lradc_disable_ts(lradc);
>  	input_unregister_device(lradc->ts_input);
>  }
>  
> @@ -660,30 +1074,23 @@ static irqreturn_t mxs_lradc_handle_irq(int irq, void *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;
> +		LRADC_CTRL1_TOUCH_DETECT_IRQ |
> +		LRADC_CTRL1_LRADC_IRQ(2) |
> +		LRADC_CTRL1_LRADC_IRQ(3) |
> +		LRADC_CTRL1_LRADC_IRQ(4) |
> +		LRADC_CTRL1_LRADC_IRQ(5);
>  
>  	if (!(reg & mxs_lradc_irq_mask(lradc)))
>  		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) {
> -		mxs_lradc_reg_clear(lradc, ts_irq_mask, LRADC_CTRL1);
> -		if (!lradc->stop_touchscreen)
> -			schedule_work(&lradc->ts_work);
> -	}
> +	if (lradc->use_touchscreen && (reg & ts_irq_mask))
> +		mxs_lradc_handle_touch(lradc);
>  
>  	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);
>  
> -	mxs_lradc_reg_clear(lradc, reg & mxs_lradc_irq_mask(lradc), LRADC_CTRL1);
> -
>  	return IRQ_HANDLED;
>  }
>  
> @@ -978,6 +1385,17 @@ static const struct of_device_id mxs_lradc_dt_ids[] = {
>  };
>  MODULE_DEVICE_TABLE(of, mxs_lradc_dt_ids);
>  
> +static int mxs_lradc_probe_touchscreen(struct mxs_lradc *lradc,
> +						struct device_node *lradc_node)
> +{
> +	/* TODO retrieve from device tree */
> +	lradc->over_sample_cnt = 4;
> +	lradc->over_sample_delay = 2;
> +	lradc->settling_delay = 10;
> +
> +	return 0;
> +}
> +
>  static int mxs_lradc_probe(struct platform_device *pdev)
>  {
>  	const struct of_device_id *of_id =
> @@ -990,7 +1408,7 @@ static int mxs_lradc_probe(struct platform_device *pdev)
>  	struct iio_dev *iio;
>  	struct resource *iores;
>  	uint32_t ts_wires = 0;
> -	int ret = 0;
> +	int ret = 0, touch_ret;
>  	int i;
>  
>  	/* Allocate the IIO device. */
> @@ -1010,7 +1428,7 @@ static int mxs_lradc_probe(struct platform_device *pdev)
>  	if (IS_ERR(lradc->base))
>  		return PTR_ERR(lradc->base);
>  
> -	INIT_WORK(&lradc->ts_work, mxs_lradc_ts_work);
> +	touch_ret = mxs_lradc_probe_touchscreen(lradc, node);
>  
>  	/* Check if touchscreen is enabled in DT. */
>  	ret = of_property_read_u32(node, "fsl,lradc-touchscreen-wires",
> @@ -1073,9 +1491,11 @@ static int mxs_lradc_probe(struct platform_device *pdev)
>  		goto err_dev;
>  
>  	/* Register the touchscreen input device. */
> -	ret = mxs_lradc_ts_register(lradc);
> -	if (ret)
> -		goto err_dev;
> +	if (touch_ret == 0) {
> +		ret = mxs_lradc_ts_register(lradc);
> +		if (ret)
> +			goto err_dev;
> +	}
>  
>  	/* Register IIO device. */
>  	ret = iio_device_register(iio);
>