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Commit 0b7018aa authored by Imre Deak's avatar Imre Deak Committed by Dmitry Torokhov
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Input: ads7846 - debouncing and rudimentary sample filtering 



Some touchscreens seem to oscillate heavily for a while after touching
the screen.  Implement support for sampling the screen until we get two
consecutive values that are close enough.

Signed-off-by: default avatarImre Deak <imre.deak@nokia.com>
Signed-off-by: default avatarJuha Yrjola <juha.yrjola@nokia.com>
Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent 53a0ef89

drivers/input/touchscreen/ads7846.c

+118 −38
Original line number Diff line number Diff line
@@ -77,7 +77,13 @@ struct ads7846 { 
	struct ts_event		tc;



	struct spi_transfer	xfer[10];

	struct spi_message	msg;

	struct spi_message	msg[5];

	int			msg_idx;

	int			read_cnt;

	int			last_read;



	u16			debounce_max;

	u16			debounce_tol;



	spinlock_t		lock;

	struct timer_list	timer;		/* P: lock */
@@ -167,7 +173,7 @@ static int ads7846_read12_ser(struct device *dev, unsigned command) 
	if (!req)

		return -ENOMEM;



	INIT_LIST_HEAD(&req->msg.transfers);

	spi_message_init(&req->msg);



	/* activate reference, so it has time to settle; */

	req->ref_on = REF_ON;
@@ -344,31 +350,76 @@ static void ads7846_rx(void *ads) 
	spin_unlock_irqrestore(&ts->lock, flags);

}



static void ads7846_debounce(void *ads)

{

	struct ads7846		*ts = ads;

	struct spi_message	*m;

	struct spi_transfer	*t;

	u16			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++;

		ts->last_read = val;

	} else {

		/* Go for the next read */

		ts->msg_idx++;

		ts->read_cnt = 0;

		m++;

	}

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

	if (status)

		dev_err(&ts->spi->dev, "spi_async --> %d\n",

				status);

}



static void ads7846_timer(unsigned long handle)

{

	struct ads7846	*ts = (void *)handle;

	int		status = 0;



	ts->msg_idx = 0;

	status = spi_async(ts->spi, &ts->msg[0]);

	if (status)

		dev_err(&ts->spi->dev, "spi_async --> %d\n", status);

}



static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)

{

	struct ads7846 *ts = handle;

	unsigned long flags;

	int r = IRQ_HANDLED;



	spin_lock_irqsave(&ts->lock, flags);

	if (!ts->pending) {

		ts->pending = 1;

	if (ts->irq_disabled)

		r = IRQ_HANDLED;

	else {

		if (!ts->irq_disabled) {

			/* REVISIT irq logic for many ARM chips has cloned a

			 * bug wherein disabling an irq in its handler won't

			 * work;(it's disabled lazily, and too late to work.

			 * until all their irq logic is fixed, we must shadow

			 * that state here.

			 */

			ts->irq_disabled = 1;



			disable_irq(ts->spi->irq);

		}

		status = spi_async(ts->spi, &ts->msg);

		if (status)

			dev_err(&ts->spi->dev, "spi_async --> %d\n",

					status);

		if (!ts->pending) {

			ts->pending = 1;

			mod_timer(&ts->timer, jiffies);

		}

	spin_unlock_irqrestore(&ts->lock, flags);

	}



static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)

{

	ads7846_timer((unsigned long) handle);

	return IRQ_HANDLED;

	spin_unlock_irqrestore(&ts->lock, flags);

	return r;

}



/*--------------------------------------------------------------------------*/
@@ -426,6 +477,7 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	struct ads7846			*ts;

	struct input_dev		*input_dev;

	struct ads7846_platform_data	*pdata = spi->dev.platform_data;

	struct spi_message		*m;

	struct spi_transfer		*x;

	int				err;
@@ -472,6 +524,8 @@ 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;



	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
@@ -495,72 +549,98 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	/* set up the transfers to read touchscreen state; this assumes we

	 * use formula #2 for pressure, not #3.

	 */

	INIT_LIST_HEAD(&ts->msg.transfers);

	m = &ts->msg[0];

	x = ts->xfer;



	spi_message_init(m);



	/* y- still on; turn on only y+ (and ADC) */

	ts->read_y = READ_Y;

	x->tx_buf = &ts->read_y;

	x->len = 1;

	spi_message_add_tail(x, &ts->msg);

	spi_message_add_tail(x, m);



	x++;

	x->rx_buf = &ts->tc.y;

	x->len = 2;

	spi_message_add_tail(x, &ts->msg);

	spi_message_add_tail(x, m);



	m->complete = ads7846_debounce;

	m->context = ts;



	m++;

	spi_message_init(m);



	/* turn y- off, x+ on, then leave in lowpower */

	x++;

	ts->read_x = READ_X;

	x->tx_buf = &ts->read_x;

	x->len = 1;

	spi_message_add_tail(x, m);



	x++;

	x->rx_buf = &ts->tc.x;

	x->len = 2;

	spi_message_add_tail(x, m);



	m->complete = ads7846_debounce;

	m->context = ts;



	/* turn y+ off, x- on; we'll use formula #2 */

	if (ts->model == 7846) {

		m++;

		spi_message_init(m);



		x++;

		ts->read_z1 = READ_Z1;

		x->tx_buf = &ts->read_z1;

		x->len = 1;

		spi_message_add_tail(x, &ts->msg);

		spi_message_add_tail(x, m);



		x++;

		x->rx_buf = &ts->tc.z1;

		x->len = 2;

		spi_message_add_tail(x, &ts->msg);

		spi_message_add_tail(x, m);



		m->complete = ads7846_debounce;

		m->context = ts;



		m++;

		spi_message_init(m);



		x++;

		ts->read_z2 = READ_Z2;

		x->tx_buf = &ts->read_z2;

		x->len = 1;

		spi_message_add_tail(x, &ts->msg);

		spi_message_add_tail(x, m);



		x++;

		x->rx_buf = &ts->tc.z2;

		x->len = 2;

		spi_message_add_tail(x, &ts->msg);

	}



	/* turn y- off, x+ on, then leave in lowpower */

	x++;

	ts->read_x = READ_X;

	x->tx_buf = &ts->read_x;

	x->len = 1;

	spi_message_add_tail(x, &ts->msg);

		spi_message_add_tail(x, m);



	x++;

	x->rx_buf = &ts->tc.x;

	x->len = 2;

	spi_message_add_tail(x, &ts->msg);

		m->complete = ads7846_debounce;

		m->context = ts;

	}



	/* power down */

	m++;

	spi_message_init(m);



	x++;

	ts->pwrdown = PWRDOWN;

	x->tx_buf = &ts->pwrdown;

	x->len = 1;

	spi_message_add_tail(x, &ts->msg);

	spi_message_add_tail(x, m);



	x++;

	x->rx_buf = &ts->dummy;

	x->len = 2;

	CS_CHANGE(*x);

	spi_message_add_tail(x, &ts->msg);

	spi_message_add_tail(x, m);



	ts->msg.complete = ads7846_rx;

	ts->msg.context = ts;

	m->complete = ads7846_rx;

	m->context = ts;



	if (request_irq(spi->irq, ads7846_irq,

			SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,

include/linux/spi/ads7846.h

+3 −0
Original line number Diff line number Diff line
@@ -14,5 +14,8 @@ struct ads7846_platform_data { 
	u16	x_min, x_max;

	u16	y_min, y_max;

	u16	pressure_min, pressure_max;



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

	u16	debounce_tol;		/* tolerance used for filtering */

};