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Commit d5b415c9 authored by Imre Deak's avatar Imre Deak Committed by Dmitry Torokhov
Browse files

Input: ads7846 - improve filtering for thumb press accuracy 



Providing more accurate coordinates for thumb press requires additional
steps in the filtering logic:

- Ignore samples found invalid by the debouncing logic, or the ones that
  have out of bound pressure value.
- Add a parameter to repeat debouncing, so that more then two consecutive
  good readings are required for a valid sample.

Signed-off-by: default avatarImre Deak <imre.deak@nokia.com>
Acked-by: default avatarJuha Yrjola <juha.yrjola@nokia.com>
Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent ae82d5ab

drivers/input/touchscreen/ads7846.c

+57 −15
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ struct ts_event { 
	__be16 x;

	__be16 y;

	__be16 z1, z2;

	int    ignore;

};



struct ads7846 {
@@ -81,6 +82,7 @@ struct ads7846 { 
	u16			model;

	u16			vref_delay_usecs;

	u16			x_plate_ohms;

	u16			pressure_max;



	u8			read_x, read_y, read_z1, read_z2, pwrdown;

	u16			dummy;		/* for the pwrdown read */
@@ -88,12 +90,15 @@ struct ads7846 { 


	struct spi_transfer	xfer[10];

	struct spi_message	msg[5];

	struct spi_message	*last_msg;

	int			msg_idx;

	int			read_cnt;

	int			read_rep;

	int			last_read;



	u16			debounce_max;

	u16			debounce_tol;

	u16			debounce_rep;



	spinlock_t		lock;

	struct timer_list	timer;		/* P: lock */
@@ -354,6 +359,14 @@ static void ads7846_rx(void *ads) 
	} else

		Rt = 0;



	/* Sample found inconsistent by debouncing or pressure is beyond

	* the maximum. Don't report it to user space, repeat at least

	* once more the measurement */

	if (ts->tc.ignore || Rt > ts->pressure_max) {

		mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);

		return;

	}



	/* NOTE:  "pendown" is inferred from pressure; we don't rely on

	 * being able to check nPENIRQ status, or "friendly" trigger modes

	 * (both-edges is much better than just-falling or low-level).
@@ -402,25 +415,45 @@ static void ads7846_debounce(void *ads) 
	struct ads7846		*ts = ads;

	struct spi_message	*m;

	struct spi_transfer	*t;

	u16			val;

	int			val;

	int			status;



	m = &ts->msg[ts->msg_idx];

	t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);

	val = (*(u16 *)t->rx_buf) >> 3;



	if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol

				&& ts->read_cnt < ts->debounce_max)) {

		/* Repeat it, if this was the first read or the read wasn't

		 * consistent enough

		 */

		ts->read_cnt++;

	if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol)) {

		/* Repeat it, if this was the first read or the read

		 * wasn't consistent enough. */

		if (ts->read_cnt < ts->debounce_max) {

			ts->last_read = val;

			ts->read_cnt++;

		} else {

		/* Go for the next read */

			/* Maximum number of debouncing reached and still

			 * not enough number of consistent readings. Abort

			 * the whole sample, repeat it in the next sampling

			 * period.

			 */

			ts->tc.ignore = 1;

			ts->read_cnt = 0;

			/* Last message will contain ads7846_rx() as the

			 * completion function.

			 */

			m = ts->last_msg;

		}

		/* Start over collecting consistent readings. */

		ts->read_rep = 0;

	} else {

		if (++ts->read_rep > ts->debounce_rep) {

			/* Got a good reading for this coordinate,

			 * go for the next one. */

			ts->tc.ignore = 0;

			ts->msg_idx++;

			ts->read_cnt = 0;

			ts->read_rep = 0;

			m++;

		} else

			/* Read more values that are consistent. */

			ts->read_cnt++;

	}

	status = spi_async(ts->spi, m);

	if (status)
@@ -609,8 +642,15 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	ts->model = pdata->model ? : 7846;

	ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;

	ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;

	ts->debounce_max = pdata->debounce_max ? : 1;

	ts->debounce_tol = pdata->debounce_tol ? : 10;

	ts->pressure_max = pdata->pressure_max ? : ~0;

	if (pdata->debounce_max) {

		ts->debounce_max = pdata->debounce_max;

		ts->debounce_tol = pdata->debounce_tol;

		ts->debounce_rep = pdata->debounce_rep;

		if (ts->debounce_rep > ts->debounce_max + 1)

			ts->debounce_rep = ts->debounce_max - 1;

	} else

		ts->debounce_tol = ~0;

	ts->get_pendown_state = pdata->get_pendown_state;



	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
@@ -728,6 +768,8 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	m->complete = ads7846_rx;

	m->context = ts;



	ts->last_msg = m;



	if (request_irq(spi->irq, ads7846_irq,

			SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,

			spi->dev.bus_id, ts)) {

include/linux/spi/ads7846.h

+4 −2
Original line number Diff line number Diff line
@@ -15,9 +15,11 @@ struct ads7846_platform_data { 
	u16	y_min, y_max;

	u16	pressure_min, pressure_max;



	u16	debounce_max;		/* max number of readings per sample */

	u16	debounce_max;		/* max number of additional readings

					 * per sample */

	u16	debounce_tol;		/* tolerance used for filtering */



	u16	debounce_rep;		/* additional consecutive good readings

					 * required after the first two */

	int	(*get_pendown_state)(void);

};