Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755045AbdDJPhP (ORCPT ); Mon, 10 Apr 2017 11:37:15 -0400 Received: from mx2.suse.de ([195.135.220.15]:38482 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754757AbdDJPfC (ORCPT ); Mon, 10 Apr 2017 11:35:02 -0400 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Brendan McGrath , Jiri Kosina , Jiri Slaby Subject: [PATCH 3.12 137/142] HID: i2c-hid: Add sleep between POWER ON and RESET Date: Mon, 10 Apr 2017 17:33:38 +0200 Message-Id: <1ea5533f37e01a399689e7bb92f723ca626526c8.1491838390.git.jslaby@suse.cz> X-Mailer: git-send-email 2.12.2 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1822 Lines: 52 From: Brendan McGrath 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit a89af4abdf9b353cdd6f61afc0eaaac403304873 upstream. Support for the Asus Touchpad was recently added. It turns out this device can fail initialisation (and become unusable) when the RESET command is sent too soon after the POWER ON command. Unfortunately the i2c-hid specification does not specify the need for a delay between these two commands. But it was discovered the Windows driver has a 1ms delay. As a result, this patch modifies the i2c-hid module to add a sleep inbetween the POWER ON and RESET commands which lasts between 1ms and 5ms. See https://github.com/vlasenko/hid-asus-dkms/issues/24 for further details. Signed-off-by: Brendan McGrath Reviewed-by: Benjamin Tissoires Signed-off-by: Jiri Kosina Signed-off-by: Jiri Slaby --- drivers/hid/i2c-hid/i2c-hid.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c index 0c65412cf5d4..c695689cfed0 100644 --- a/drivers/hid/i2c-hid/i2c-hid.c +++ b/drivers/hid/i2c-hid/i2c-hid.c @@ -341,6 +341,15 @@ static int i2c_hid_hwreset(struct i2c_client *client) if (ret) return ret; + /* + * The HID over I2C specification states that if a DEVICE needs time + * after the PWR_ON request, it should utilise CLOCK stretching. + * However, it has been observered that the Windows driver provides a + * 1ms sleep between the PWR_ON and RESET requests and that some devices + * rely on this. + */ + usleep_range(1000, 5000); + i2c_hid_dbg(ihid, "resetting...\n"); ret = i2c_hid_command(client, &hid_reset_cmd, NULL, 0); -- 2.12.2