[PATCH 3.14 15/29] Input: usbtouchscreen - avoid unresponsive TSC-30 touch screen

From: Greg Kroah-Hartman
Date: Sat Aug 08 2015 - 18:45:07 EST

3.14-stable review patch. If anyone has any objections, please let me know.


From: Bernhard Bender <bernhard.bender@xxxxxxxxxxxx>

commit 968491709e5b1aaf429428814fff3d932fa90b60 upstream.

This patch fixes a problem in the usbtouchscreen driver for DMC TSC-30
touch screen. Due to a missing delay between the RESET and SET_RATE
commands, the touch screen may become unresponsive during system startup or
driver loading.

According to the DMC documentation, a delay is needed after the RESET
command to allow the chip to complete its internal initialization. As this
delay is not guaranteed, we had a system where the touch screen
occasionally did not send any touch data. There was no other indication of
the problem.

The patch fixes the problem by adding a 150ms delay between the RESET and
SET_RATE commands.

Suggested-by: Jakob Mustafa <jakob.mustafa@xxxxxxxxxxxx>
Signed-off-by: Bernhard Bender <bernhard.bender@xxxxxxxxxxxx>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/input/touchscreen/usbtouchscreen.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c
@@ -625,6 +625,9 @@ static int dmc_tsc10_init(struct usbtouc
goto err_out;

+ /* TSC-25 data sheet specifies a delay after the RESET command */
+ msleep(150);
/* set coordinate output rate */
buf[0] = buf[1] = 0xFF;
ret = usb_control_msg(dev, usb_rcvctrlpipe (dev, 0),

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