Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753659AbbBYUp3 (ORCPT ); Wed, 25 Feb 2015 15:45:29 -0500 Received: from mail-wi0-f172.google.com ([209.85.212.172]:50181 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752880AbbBYUpZ (ORCPT ); Wed, 25 Feb 2015 15:45:25 -0500 From: Pali =?utf-8?q?Roh=C3=A1r?= To: Mario Limonciello Subject: Re: [PATCH] Add a quirk for the Dell XPS 13 (2015) when in PS/2 mode. Date: Wed, 25 Feb 2015 21:45:22 +0100 User-Agent: KMail/1.13.7 (Linux/3.13.0-46-generic; KDE/4.14.2; x86_64; ; ) Cc: Dmitry Torokhov , LKML , "linux-input@vger.kernel.org" , Rob References: <1424310180-2512-1-git-send-email-mario_limonciello@dell.com> <201502202141.16017@pali> <54EE1917.4020805@dell.com> In-Reply-To: <54EE1917.4020805@dell.com> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart2211052.m6BLW1Q3dA"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <201502252145.22577@pali> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3406 Lines: 83 --nextPart2211052.m6BLW1Q3dA Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Wednesday 25 February 2015 19:48:55 Mario Limonciello wrote: > On 02/20/2015 02:41 PM, Pali Roh=C3=A1r wrote: > > On Friday 20 February 2015 20:56:23 Mario Limonciello wrote: > >=20 > > resetafter=3D0 means to never reset (even if driver receive > > e.g thousand invalid packets). I think this is very > > dangerous if there will be other bugs either in linux > > driver or some other HW problems. > >=20 > > For ALPS issue I added resetafter =3D pktsize * 2 (Allow 2 > > invalid packets without resetting device). Cannot you find > > something similar for synaptics touchpads on XPS? (pktsize > > for ALPS is 6, no idea how big are synaptics packets). >=20 > Pali, >=20 > I've done some experimentation with increasing the size to > resetafter to up to pktsize * 4. It will decrease the number > of occurrences of this problem, but the problem still occurs > eventually. pktsize for synaptics is 6 as well. Would you > recommend to continue to go higher than that? Since > out_of_sync_cnt is reset when a full packet gets received, > some arbitrarily high number should likely fix it to. >=20 > That being said, if you try to more closely follow what > Windows does for the mouse, it's not issuing a reconnect no > matter how much bad data is received. I believe problem is similar to one as with ALPS devices. Driver=20 always receive 6 bytes packet of data (no new byte is inserted=20 and no byte is never lost), just one byte in packet is incorrect=20 (does not match specification). Setting resetafter to > 0 prevent problems when driver enters=20 into undefined state (either by bug in driver of other SW/HW=20 problem). So I think setting resetafter to 0 is not good idea. But if we know that setting resetafter to 4*pktsize is not enough=20 (e.g. with experimenting you saw that driver received more then 4=20 invalid packets consecutively), set it to higher value. I think it is still good idea to ignore maximally as many packets=20 which can be received in time which is equal to resetting device. E.g. when period of time in which we are dropping all packets is=20 higher then time needed to reset touchpad, we should stop=20 dropping packets and immediately reset touchpad. In this case we=20 could hit maybe problem in driver (there can be bugs) or touchpad=20 is in some bad state and out-of-sync... So if your tests show that there are never invalid 10 packets=20 consecutively, then set resetafter to 10 packets. Value 10 is=20 still not high and if it fix problem with touchpad I think it is=20 acceptable. But rather ask Dmitry what he thinks about it. This=20 is just my opinion. =2D-=20 Pali Roh=C3=A1r pali.rohar@gmail.com --nextPart2211052.m6BLW1Q3dA Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iEYEABECAAYFAlTuNGIACgkQi/DJPQPkQ1JeeQCguEdNBsag3wj3293x5UBTzvWx S7EAoJD6wu8tYUnz+u2+Qw3HmajK19Xz =CM43 -----END PGP SIGNATURE----- --nextPart2211052.m6BLW1Q3dA-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/