From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751703AbdAFWTb (ORCPT ); Fri, 6 Jan 2017 17:19:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38518 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S939904AbdAFWCi (ORCPT ); Fri, 6 Jan 2017 17:02:38 -0500 Date: Fri, 6 Jan 2017 23:02:32 +0100 From: Benjamin Tissoires To: Brendan McGrath Cc: Jiri Kosina , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Victor Vlasenko , Frederik Wenigwieser Subject: Re: [PATCHv3] HID: i2c-hid: Add sleep between POWER ON and RESET Message-ID: <20170106220232.GB23721@mail.corp.redhat.com> References: <20170106081144.GE15702@mail.corp.redhat.com> <1483736498-7805-1-git-send-email-redmcg@redmandi.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1483736498-7805-1-git-send-email-redmcg@redmandi.dyndns.org> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 06 Jan 2017 22:02:38 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Jan 07 2017 or thereabouts, Brendan McGrath wrote: > 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 > --- > Changes since v2: > - added comments to explain the reason for the sleep > Looks good now, thanks! Reviewed-by: Benjamin Tissoires Cheers, Benjamin > 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 844662c..d5288f3 100644 > --- a/drivers/hid/i2c-hid/i2c-hid.c > +++ b/drivers/hid/i2c-hid/i2c-hid.c > @@ -426,6 +426,15 @@ static int i2c_hid_hwreset(struct i2c_client *client) > 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); > -- > 2.7.4 >