From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754438AbaJVQf6 (ORCPT ); Wed, 22 Oct 2014 12:35:58 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:47519 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753710AbaJVQf5 (ORCPT ); Wed, 22 Oct 2014 12:35:57 -0400 From: Pali =?utf-8?q?Roh=C3=A1r?= To: Guenter Roeck Subject: Re: [PATCH] i8k: Ignore temperature sensors which report invalid values Date: Wed, 22 Oct 2014 18:35:53 +0200 User-Agent: KMail/1.13.7 (Linux/3.17.0-031700rc6-generic; KDE/4.14.1; x86_64; ; ) Cc: Arnd Bergmann , "Greg Kroah-Hartman" , linux-kernel@vger.kernel.org, Steven Honeyman References: <1413730014-30945-1-git-send-email-pali.rohar@gmail.com> <201410221429.06699@pali> <20141022161947.GA31045@roeck-us.net> In-Reply-To: <20141022161947.GA31045@roeck-us.net> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart4212353.Ar6uPn5LfQ"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <201410221835.53526@pali> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --nextPart4212353.Ar6uPn5LfQ Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Wednesday 22 October 2014 18:19:47 Guenter Roeck wrote: > On Wed, Oct 22, 2014 at 02:29:06PM +0200, Pali Roh=C3=A1r wrote: > > On Tuesday 21 October 2014 06:27:23 Guenter Roeck wrote: > > > On 10/20/2014 09:46 AM, Pali Roh=C3=A1r wrote: > > > > Ok, I will describe my problem. Guenter, maybe you can > > > > find another solution/fix for it. > > > >=20 > > > > Calling i8k_get_temp(3) on my laptop without > > > > I8K_TEMPERATURE_BUG always returns value 193 (which is > > > > above I8K_MAX_TEMP). > > > >=20 > > > > When I8K_TEMPERATURE_BUG is enabled (by default) then > > > > i8k_get_temp(3) returns value from prev[3] and store new > > > > value I8K_TEMPERATURE_BUG to prev[3]. Value in prev[3] > > > > is initialized to 0. > > > >=20 > > > > What I want to achieve is: when i8k_get_temp() for > > > > particular sensor id always returns invalid value (> > > > > I8K_MAX_TEMP) then we should totally ignore sensor with > > > > that id and do not export it via hwmon. > > > >=20 > > > > My solution is: initialize prev[id] to I8K_MAX_TEMP, so > > > > on invalid data first call to i8k_get_temp(id) returns > > > > I8K_MAX_TEMP. Then in i8k_init_hwmon check if value is > > > > < I8K_MAX_TEMP and if not ignore sensor id. > > > >=20 > > > > Guenter, it is clear now? Are you ok that we should > > > > ignore sensor if always report value above > > > > I8K_MAX_TEMP? If you do not like my solution/patch for > > > > it, can you specify how other can it be fixed? > > >=20 > > > I still don't see the point in initializing prev[]. > >=20 > > Now prev[] is initialized to 0. It means that first call > > i8k_get_temp() (with sensor id which return value > > > I8K_MAX_TEMP) returns 0. Second and other calls returns > > I8K_MAX_TEMP. > >=20 > > So point is to return same value for first and other calls. >=20 > Yes, I realized that after I sent my previous mail. >=20 > > > Yes, I am ok with ignoring sensor values if the reported > > > temperature is above I8K_MAX_TEMP. I am just not sure if > > > we should check against I8K_MAX_TEMP or against, say, > > > 192. Reason is that we do know that the sensor can > > > erroneously return 0x99 on some systems once in a while. > > > We would not want to ignore those sensors just because > > > they happen to report 0x99 during initialization. > > >=20 > > > So maybe make it > > >=20 > > > if (err >=3D 0 && err < 192) > > >=20 > > > and add a note before the first if(), explaining that > > > higher values suggest that there is no sensor attached. > > >=20 > > > Thanks, > > > Guenter > >=20 > > Right, now we need to decide which magic constant to use... > >=20 > > And now I found another problem :-) > >=20 > > On my laptop i8k_get_temp(3) not always return value 193. It > > is only when AMD graphics card is turned off. When card is > > on i8k_get_temp(3) returns same value as temperature hwmon > > part from radeon DRM driver. >=20 > Can you turn the GPU on or off during runtime ? > That would make it really tricky to handle the situation. >=20 Yes. New laptops with Nvidia Optimus or AMD PowerXpress or Enduro=20 technology are designed to automatically turn off secondary GPU=20 when is not in use. And nouveau/radeon drivers together with=20 vga_switcheroo implements this dynamic power on/off. > > So it looks like that on my laptop i8k sensor with id 3 > > reports GPU temperature. > >=20 > > When card is turned off radeon driver reports -EINVAL for > > temperature hwmon sysnode. > >=20 > > So now I think i8k could not ignore sensor totally as it can > > be mapped to some HW which can be dynamically turned on/off > > (like my graphics card). > >=20 > > So what do you think about reporting -EINVAL instead > > I8K_MAX_TEMP when dell SMM returns value above > > I8K_MAX_TEMP? >=20 > -EINVAL is supposed to mean "Invalid Argument", so it really > has ia different semantics. We could use -ENXIO, "No such > device or address", which seems more appropriate. >=20 I prefer to use -EINVAL because other driver (radeon) is using it=20 and userspace "sensors" programs handle EINVAL and show "N/A" in=20 output instead reporting some error about reading value. If=20 nothing else consistency (with other drivers) is my argument. > Overall, I think the entire error handling is broken and > should be replaced. One option would be to explicitly check > for 0x99 and, if detected, go to sleep for, say, 100ms and > try again. If it still fails, and for all other bad values, > return -ENXIO. Then the calling code can either return the > error to user space in the show function, or not install the > sensor in the probe function. >=20 > Does that make sense ? >=20 Yes, replacing error handling with retry call (after some sleep)=20 is better then current code (which returns previous value or=20 returns I8K_MAX_TEMP). But your solution not install the sensor if probe fails on bad=20 value does not solve problem that i8k.ko is loading at time when=20 GPU card is turned off. I think current check for installing sensor (err < 0) is enough=20 and when invalid value (> I8K_MAX_TEMP) is returned just do not=20 show this value for userspace in hwmon sysnode. > Thanks, > Guenter =2D-=20 Pali Roh=C3=A1r pali.rohar@gmail.com --nextPart4212353.Ar6uPn5LfQ 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) iEYEABECAAYFAlRH3OkACgkQi/DJPQPkQ1IRnwCfVRvJNFQMmZjepP4wh4V7S3dk IyEAoI00h5c6AMV0NcgRWTqRYrE3EqYC =CnaX -----END PGP SIGNATURE----- --nextPart4212353.Ar6uPn5LfQ--