Input: ads7846 - re-check pendown status before reporting events
Pendown status from the PENIRQ pin is currently read only at the beginning
of a sample set. If the pen is lifted just after sampling has began then
sampled values become wrong.
This patch adds an optional platform penirq_recheck_delay attribute. If
non-zero, samples are only reported to the input subsystem if PENIRQ is
still active that long after the samples taken.
Signed-off-by: Semih Hazar <semih.hazar@indefia.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 103ee6a..96581d0 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -107,6 +107,8 @@
u16 debounce_tol;
u16 debounce_rep;
+ u16 penirq_recheck_delay_usecs;
+
spinlock_t lock;
struct hrtimer timer;
unsigned pendown:1; /* P: lock */
@@ -553,6 +555,15 @@
return;
}
+ /* Maybe check the pendown state before reporting. This discards
+ * false readings when the pen is lifted.
+ */
+ if (ts->penirq_recheck_delay_usecs) {
+ udelay(ts->penirq_recheck_delay_usecs);
+ if (!ts->get_pendown_state())
+ Rt = 0;
+ }
+
/* NOTE: We can't rely on the pressure to determine the pen down
* state, even this controller has a pressure sensor. The pressure
* value can fluctuate for quite a while after lifting the pen and
@@ -896,6 +907,10 @@
ts->filter = ads7846_no_filter;
ts->get_pendown_state = pdata->get_pendown_state;
+ if (pdata->penirq_recheck_delay_usecs)
+ ts->penirq_recheck_delay_usecs =
+ pdata->penirq_recheck_delay_usecs;
+
snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
input_dev->name = "ADS784x Touchscreen";
diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
index a44fa7a..334d314 100644
--- a/include/linux/spi/ads7846.h
+++ b/include/linux/spi/ads7846.h
@@ -24,6 +24,12 @@
*/
u16 settle_delay_usecs;
+ /* If set to non-zero, after samples are taken this delay is applied
+ * and penirq is rechecked, to help avoid false events. This value
+ * is affected by the material used to build the touch layer.
+ */
+ u16 penirq_recheck_delay_usecs;
+
u16 x_plate_ohms;
u16 y_plate_ohms;