Input: usbtouchscreen - avoid unresponsive TSC-30 touch screen

berdroid · dtor · commit 968491709e5b · 2015-07-23T14:43:17.000-07:00
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.

Cc: stable@vger.kernel.org
Suggested-by: Jakob Mustafa &lt;jakob.mustafa@bytecmed.com&gt;
Signed-off-by: Bernhard Bender &lt;bernhard.bender@bytecmed.com&gt;
Signed-off-by: Dmitry Torokhov &lt;dmitry.torokhov@gmail.com&gt;
diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
@@ -627,6 +627,9 @@ 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),

Original file line number	Diff line number	Diff line change
`@@ -627,6 +627,9 @@ static int dmc_tsc10_init(struct usbtouch_usb *usbtouch)`
`627`	`627`	`goto err_out;`
`628`	`628`	`}`
`629`	`629`
	`630`	`+ /* TSC-25 data sheet specifies a delay after the RESET command */`
	`631`	`+ msleep(150);`
	`632`	`+`
`630`	`633`	`/* set coordinate output rate */`
`631`	`634`	`buf[0] = buf[1] = 0xFF;`
`632`	`635`	`ret = usb_control_msg(dev, usb_rcvctrlpipe (dev, 0),`