[PATCH 4.14 097/242] Input: ads7846 - fix race that causes missing releases

Greg Kroah-Hartman
2020-12-28T16:22:46Z

From: David Jander <david@protonic.nl>

[ Upstream commit e52cd628a03f72a547dbf90ccb703ee64800504a ]

If touchscreen is released while busy reading HWMON device, the release
can be missed. The IRQ thread is not started because no touch is active
and BTN_TOUCH release event is never sent.

Fixes: f5a28a7d4858f94a ("Input: ads7846 - avoid pen up/down when reading hwmon")
Co-developed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: David Jander <david@protonic.nl>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20201027105416.18773-1-o.rempel@pengutronix.de
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/input/touchscreen/ads7846.c | 44 +++++++++++++++++------------
1 file changed, 26 insertions(+), 18 deletions(-)

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index a2f45aefce08a..0fbad337e45a3 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -199,6 +199,26 @@ struct ads7846 {
#define REF_ON (READ_12BIT_DFR(x, 1, 1))
#define REF_OFF (READ_12BIT_DFR(y, 0, 0))

+static int get_pendown_state(struct ads7846 *ts)
+{
+ if (ts->get_pendown_state)
+ return ts->get_pendown_state();
+
+ return !gpio_get_value(ts->gpio_pendown);
+}
+
+static void ads7846_report_pen_up(struct ads7846 *ts)
+{
+ struct input_dev *input = ts->input;
+
+ input_report_key(input, BTN_TOUCH, 0);
+ input_report_abs(input, ABS_PRESSURE, 0);
+ input_sync(input);
+
+ ts->pendown = false;
+ dev_vdbg(&ts->spi->dev, "UP\n");
+}
+
/* Must be called with ts->lock held */
static void ads7846_stop(struct ads7846 *ts)
{
@@ -215,6 +235,10 @@ static void ads7846_stop(struct ads7846 *ts)
static void ads7846_restart(struct ads7846 *ts)
{
if (!ts->disabled && !ts->suspended) {
+ /* Check if pen was released since last stop */
+ if (ts->pendown && !get_pendown_state(ts))
+ ads7846_report_pen_up(ts);
+
/* Tell IRQ thread that it may poll the device. */
ts->stopped = false;
mb();
@@ -605,14 +629,6 @@ static const struct attribute_group ads784x_attr_group = {

/*--------------------------------------------------------------------------*/

-static int get_pendown_state(struct ads7846 *ts)
-{
- if (ts->get_pendown_state)
- return ts->get_pendown_state();
-
- return !gpio_get_value(ts->gpio_pendown);
-}
-
static void null_wait_for_sync(void)
{
}
@@ -871,16 +887,8 @@ static irqreturn_t ads7846_irq(int irq, void *handle)
msecs_to_jiffies(TS_POLL_PERIOD));
}

- if (ts->pendown && !ts->stopped) {
- struct input_dev *input = ts->input;
-
- input_report_key(input, BTN_TOUCH, 0);
- input_report_abs(input, ABS_PRESSURE, 0);
- input_sync(input);
-
- ts->pendown = false;
- dev_vdbg(&ts->spi->dev, "UP\n");
- }
+ if (ts->pendown && !ts->stopped)
+ ads7846_report_pen_up(ts);

return IRQ_HANDLED;
}
--
2.27.0