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

Jani Nikula jani.nikula at intel.com
Thu Feb 13 23:09:52 PST 2014

On Thu, 13 Feb 2014, Luis Ortega <luiorpe1 at upv.es> wrote:

On Thu, Feb 13, 2014 at 05:24:23PM +0100, Luis Ortega wrote:

> 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 Please provide dmesg with drm.debug=0xe with 3.14-rc2. I've booted with the kernel args drm.debug=0xe logbuflen=16M. I've attached the following files for your inspection: dmesg.txt - dmesg output lspci.txt - output of: su -c 'lspci -nn' /var/log/Xorg.0.log Ask me if there is anything else I can do to help.

It seems that it will be better to track this in bugzilla rather than the mailing lists. Please file a bug on DRM/Intel component at https://bugs.freedesktop.org/enter_bug.cgi?product=DRI. Attach these files.

Also, please include the output of 'ls /sys/class/backlight'. The Xorg.0.log indicates you have a backlight device of "platform" type which should be preferred over the "raw" intel_backlight:

[ 29.333] (--) intel(0): found backlight control interface eeepc (type 'platform')

If you try changing backlight using the sysfs under /sys/class/backlight/ using 'sudo sh -c "echo N > brightness"' where N is a value between 0 and cat max_brightness, do the interfaces there work, intel_backlight in particular?

Please include this information in the bug.

Additionally, a register dump for both the working and non-working cases using tools/intel_reg_dumper from the intel-gpu-tools package might prove to be helpful.

BR, Jani.

-- Jani Nikula, Intel Open Source Technology Center

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