linux-kernel - [PATCH 3.16.y-ckt 099/118] Input: usbtouchscreen

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Message-Id: <1439369820-27005-100-git-send-email-luis.henriques@canonical.com>
Date:	Wed, 12 Aug 2015 09:56:41 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Bernhard Bender <bernhard.bender@...ecmed.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 099/118] Input: usbtouchscreen - avoid unresponsive TSC-30 touch screen

3.16.7-ckt16 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bernhard Bender <bernhard.bender@...ecmed.com>

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@...ecmed.com>
Signed-off-by: Bernhard Bender <bernhard.bender@...ecmed.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/input/touchscreen/usbtouchscreen.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
index a0966331a89b..c6f7e918b2b1 100644
--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c
@@ -625,6 +625,9 @@ 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),
--
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