[Regression 3.14-rc2] drm/i915: Brightness adjustment is broken in 945GM (original) (raw)

Luis Ortega luiorpe1 at upv.es
Thu Feb 13 08:24:23 PST 2014

I dare say either your bisect went sour or you don't have 945GM. Please verify your steps.

Well, what can I say? I was careful when testing and the last kernel I compiled shows the problem. I can replay the bisection if needed but if I have to start all over again it's gonna take some time. I'm compiling in the netbook and took me day and a half to finish the process.

In all honesty, along the way I met commit messages that I thought were more probable to introduce this regression. (backlight related)

Also, here's the output of lspci: 00:00.0 Host bridge: Intel Corporation Mobile 945GSE Express Memory Controller Hub (rev 03) 00:02.0 VGA compatible controller: Intel Corporation Mobile 945GSE Express Integrated Graphics Controller (rev 03) 00:02.1 Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03)

Please provide dmesg with drm.debug=0xe with 3.14-rc2.

Care to explain a bit more before I recompile 3.14-rc2? Do I need to enable some particular debug option? How do I proceed for drm.debug=0xe?

Luis

On Thu, Feb 13, 2014 at 05:04:23PM +0200, Jani Nikula wrote: On Thu, 13 Feb 2014, Luis Ortega <luiorpe1 at upv.es> wrote: > Hi, testing 3.14-rc2 I noticed I could not adjust the brightness of the > screen any longer. This problem is already present in 3.14-rc1. 3.13 works fine. > > My hardware is a netbook with intel atom and a 945GM graphics card. > > I bisected the problem down to the next commit:

I dare say either your bisect went sour or you don't have 945GM. Please verify your steps. Please provide dmesg with drm.debug=0xe with 3.14-rc2. BR, Jani. > > bc0bb9fd1c7810407ab810d204bbaecb255fddde is the first bad commit > commit bc0bb9fd1c7810407ab810d204bbaecb255fddde > Author: Jani Nikula <jani.nikula at intel.com> > Date: Thu Nov 14 12:14:29 2013 +0200 > > drm/i915: remove QUIRKNOPCHPWMENABLE > > The quirk was added as what I'd say was a stopgap measure in > > commit e85843bec6c2ea7c10ec61238396891cc2b753a9 > Author: Kamal Mostafa <kamal at canonical.com> > Date: Fri Jul 19 15:02:01 2013 -0700 > > drm/i915: quirk no PCHPWMENABLE for Dell XPS13 backlight > > without really digging into what was going on. > > Also, as mentioned in the related bug [1], having the quirk regressed > some of the machines it was supposed to fix to begin with, and there > were patches posted to disable the quirk on such machines [2]! > > The fact is, we do need the BLMPCHPWMENABLE bit set to have > backlight. With the quirk, we've relied on BIOS to have set it, and our > save/restore code to retain it. With the full backlight setup at enable, > we have no place for things that rely on previous state. > > With the per platform hooks, we've also made a change in the PCH > platform enable order: setting the backlight duty cycle between CPU and > PCH PWM enable. Some experimenting and > > commit 770c12312ad617172b1a65b911d3e6564fc5aca8 > Author: Takashi Iwai <tiwai at suse.de> > Date: Sat Aug 11 08:56:42 2012 +0200 > > drm/i915: Fix blank panel at reopening lid > > indicate that we can't set the backlight before enabling CPU PWM; the > value just won't stick. But AFAICT we should do it before enabling the > PCH PWM. > > Finally, any fallout we should fix properly, preferrably without quirks, > and absolutely without quirks that rely on existing state. With the per > platform hooks have much more flexibility to adjust the sequence as > required by platforms. > > [1] https://bugzilla.kernel.org/showbug.cgi?id=47941 > [2] http://lkml.kernel.org/r/1378229848-29113-1-git-send-email-kamal@canonical.com > > Signed-off-by: Jani Nikula <jani.nikula at intel.com> > Reviewed-by: Imre Deak <imre.deak at intel.com> > Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch> > > > Additionally, when I had narrowed the problem to around 11 commits all the > resulting kernel I compiled made the screen blink and shake from left to right > non-stop. In the -rc kernels this doesn't happen. Thought it was worth > mentioning.

-- Jani Nikula, Intel Open Source Technology Center

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