Input: usbtouchscreen - avoid unresponsive TSC-30 touch screen

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@bytecmed.com>
Signed-off-by: Bernhard Bender <bernhard.bender@bytecmed.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
index 73fd664..e26a7c3 100644 (file)
--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c
@@ -528,6 +528,9 @@ static int dmc_tsc10_init(struct usbtouch_usb *usbtouch)
                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),