[PATCH 1/1] Avoid unresponsive TSC-30 touch screen

From: Bernhard Bender <Bernhard.Bender@bytecmed.com>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
	Jakob Mustafa <Jakob.Mustafa@bytecmed.com>
Subject: [PATCH 1/1] Avoid unresponsive TSC-30 touch screen
Date: Thu, 23 Jul 2015 17:01:31 +0200	[thread overview]
Message-ID: <6B919AC79333344DB0660E3FADEB2165057496DA51FD@BYTECEXCHGSRV.bytecexchg.local> (raw)

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

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.

        Signed-off-by: Bernhard Bender <bernhard.bender@bytecmed.com>
        Suggested-by: Jakob Mustafa <jakob.mustafa@bytecmed.com>

---
Bernhard Bender
Entwicklung

Bytec Medizintechnik GmbH
Hermann-Hollerith-Str. 11
52249 Eschweiler, Germany
Tel. +49 (2403) 7829-943
www.bytecmed.com

Handelsregister Aachen: HRB 11222
Ust-ID: DE 121732719
Geschäftsführer: Dipl.-Ing. Paul Willi Coenen

diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
old mode 100644
new mode 100755
index a096633..4ebff01
--- 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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