linux-kernel - [PATCH 3.4 043/107] Input: usbtouchscreen - avoid unresponsive TSC-30 touch screen

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Message-Id: <1458115601-5762-43-git-send-email-lizf@kernel.org>
Date:	Wed, 16 Mar 2016 16:05:37 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Bernhard Bender <bernhard.bender@...ecmed.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 043/107] Input: usbtouchscreen - avoid unresponsive TSC-30 touch screen

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

3.4.111-rc1 review patch.  If anyone has any objections, please let me know.

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

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: Zefan Li <lizefan@...wei.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 ce384a4..e57eaf8 100644
--- a/drivers/input/touchscreen/usbtouchscreen.c
+++ b/drivers/input/touchscreen/usbtouchscreen.c
@@ -586,6 +586,9 @@ 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),
-- 
1.9.1