Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756173AbdGCOYb (ORCPT ); Mon, 3 Jul 2017 10:24:31 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36588 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755697AbdGCNoS (ORCPT ); Mon, 3 Jul 2017 09:44:18 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Brendan McGrath , Benjamin Tissoires , Jiri Kosina , Sasha Levin Subject: [PATCH 4.9 106/172] HID: i2c-hid: Add sleep between POWER ON and RESET Date: Mon, 3 Jul 2017 15:34:46 +0200 Message-Id: <20170703133419.264618242@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170703133414.260777365@linuxfoundation.org> References: <20170703133414.260777365@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1775 Lines: 51 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Brendan McGrath [ Upstream commit a89af4abdf9b353cdd6f61afc0eaaac403304873 ] 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: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/hid/i2c-hid/i2c-hid.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/drivers/hid/i2c-hid/i2c-hid.c +++ b/drivers/hid/i2c-hid/i2c-hid.c @@ -427,6 +427,15 @@ static int i2c_hid_hwreset(struct i2c_cl if (ret) goto out_unlock; + /* + * 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);