From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754801AbaJWQpT (ORCPT ); Thu, 23 Oct 2014 12:45:19 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:59029 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752241AbaJWQpQ (ORCPT ); Thu, 23 Oct 2014 12:45:16 -0400 Date: Thu, 23 Oct 2014 09:45:07 -0700 From: Guenter Roeck To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Steven Honeyman Subject: Re: [PATCH] i8k: Ignore temperature sensors which report invalid values Message-ID: <20141023164507.GC21343@roeck-us.net> References: <1413730014-30945-1-git-send-email-pali.rohar@gmail.com> <201410221835.53526@pali> <20141022171005.GA30530@roeck-us.net> <201410231237.35053@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <201410231237.35053@pali> User-Agent: Mutt/1.5.21 (2010-09-15) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Suspect X-CTCH-VOD: Unknown X-CTCH-Flags: 512 X-CTCH-RefID: str=0001.0A020206.5449309C.01DC,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=512,sb=0 X-CTCH-Score: 0.000 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: C_4847, X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 10 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 4 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 23, 2014 at 12:37:34PM +0200, Pali Rohár wrote: > On Wednesday 22 October 2014 19:10:05 Guenter Roeck wrote: > > On Wed, Oct 22, 2014 at 06:35:53PM +0200, Pali Rohár wrote: > > > On Wednesday 22 October 2014 18:19:47 Guenter Roeck wrote: > > > > On Wed, Oct 22, 2014 at 02:29:06PM +0200, Pali Rohár wrote: > > > > > On Tuesday 21 October 2014 06:27:23 Guenter Roeck wrote: > > > > > > On 10/20/2014 09:46 AM, Pali Rohár wrote: > > > > > > > Ok, I will describe my problem. Guenter, maybe you > > > > > > > can find another solution/fix for it. > > > > > > > > > > > > > > Calling i8k_get_temp(3) on my laptop without > > > > > > > I8K_TEMPERATURE_BUG always returns value 193 (which > > > > > > > is above I8K_MAX_TEMP). > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > 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? > > > > > > > > > > > > I still don't see the point in initializing prev[]. > > > > > > > > > > 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. > > > > > > > > > > So point is to return same value for first and other > > > > > calls. > > > > > > > > Yes, I realized that after I sent my previous mail. > > > > > > > > > > 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. > > > > > > > > > > > > So maybe make it > > > > > > > > > > > > if (err >= 0 && err < 192) > > > > > > > > > > > > and add a note before the first if(), explaining that > > > > > > higher values suggest that there is no sensor > > > > > > attached. > > > > > > > > > > > > Thanks, > > > > > > Guenter > > > > > > > > > > Right, now we need to decide which magic constant to > > > > > use... > > > > > > > > > > And now I found another problem :-) > > > > > > > > > > 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. > > > > > > > > Can you turn the GPU on or off during runtime ? > > > > That would make it really tricky to handle the situation. > > > > > > Yes. New laptops with Nvidia Optimus or AMD PowerXpress or > > > Enduro technology are designed to automatically turn off > > > secondary GPU when is not in use. And nouveau/radeon > > > drivers together with vga_switcheroo implements this > > > dynamic power on/off. > > > > > > > > So it looks like that on my laptop i8k sensor with id 3 > > > > > reports GPU temperature. > > > > > > > > > > When card is turned off radeon driver reports -EINVAL > > > > > for temperature hwmon sysnode. > > > > > > > > > > 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). > > > > > > > > > > So what do you think about reporting -EINVAL instead > > > > > I8K_MAX_TEMP when dell SMM returns value above > > > > > I8K_MAX_TEMP? > > > > > > > > -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. > > > > > > I prefer to use -EINVAL because other driver (radeon) is > > > using it and userspace "sensors" programs handle EINVAL and > > > show "N/A" in output instead reporting some error about > > > reading value. If nothing else consistency (with other > > > drivers) is my argument. > > > > Ok, if sensors implements it that way then let's do it. > > > > > > 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. > > > > > > > > Does that make sense ? > > > > > > Yes, replacing error handling with retry call (after some > > > sleep) is better then current code (which returns previous > > > value or returns I8K_MAX_TEMP). > > > > > > But your solution not install the sensor if probe fails on > > > bad value does not solve problem that i8k.ko is loading at > > > time when GPU card is turned off. > > > > Yes, the dynamics in that situation makes it a bit difficult > > to handle the situation. > > > > > I think current check for installing sensor (err < 0) is > > > enough and when invalid value (> I8K_MAX_TEMP) is returned > > > just do not show this value for userspace in hwmon sysnode. > > > > Ok with me, and agreed. > > > > Thanks, > > Guenter > > Ok, are you going to fix i8k_get_temp() function (with sleeping)? > I had hoped you would find the time to do it ;-). Sure, I can do it, but I am kind of busy right now, so it will take a while. Thanks, Guenter