Patchset "Fix Win8 backlight issue" breaks backlight on my laptop. Sometime backlight is bright, sometimes it's dark and it can't be modified with the function keys. Writing integer values into /sys/class/backlight/intel_backlight/brightness also does not work. So sometimes I am left with an unusable laptop. Patchset: http://marc.info/?t=138001608800001&r=1&w=2 Video driver: i915 HW: FUJITSU LIFEBOOK AH532/FJNBB1C, BIOS Version 1.09 05/22/2012 I was told the culprit is i915 (-> http://marc.info/?l=dri-devel&m=138024096722789&w=2) so I file this bug against i915.
It follows from what you said on mailing lists that intel_backlight doesn't work on your machine even without the patchset mentioned above. Is that correct?
We should debug this with upstream vanilla kernel, without the patches. Please use acpi_backlight=vendor kernel parameter and drm.debug=0xe module parameter. The hotkeys won't work with this, but try changing backlight through the gui and the sysfs file. Please attach dmesg all the way from boot to where you try to change backlight. Thanks.
Created attachment 110001 [details] dmesg with acpi_backlight=vendor
acpi_backlight=vendor replaces acpi_video0 with fujitsu_laptop. So now I have fujitsu_laptop and intel_backlight under /sys/class/nacklight. Gui works, function keys work. Writing into intel_backlight/brightness however does not work!
(In reply to jrg.otte from comment #4) > acpi_backlight=vendor replaces acpi_video0 with fujitsu_laptop. > So now I have fujitsu_laptop and intel_backlight under > /sys/class/nacklight. Ah, sorry, please also blacklist fujitsu-laptop while testing. Rinse and repeat.
Created attachment 110061 [details] dmesg without fujitsu-laptop ok, now neither Gui, nor function keys nor writing to intel_backlight/brightness work. Backlight can not be modified now.
Jani, Any ideas why intel_backlight doesn't work? Jörg, Please also attach acpidump: # acpidump > acpidump.txt Thanks!
Created attachment 110901 [details] acpidump
The current drm-intel-nightly branch at [1] leaves some more "breadcrumbs" about what it does with the backlight. Please try that, with backlight=vendor and blacklist fujitsu-laptop, and attach dmesg with drm.debug=0xe. Thanks. [1] http://cgit.freedesktop.org/~danvet/drm-intel/log/?h=drm-intel-nightly
Created attachment 112051 [details] dmesg kernel 3.12.0-rc5-00551-gaabd627 from drm-intel No visible change for me. backlight still not working.
Hmm. Just an idea, do you boot in pure UEFI mode, or CSM/legacy?
I think EFI mode. But I'm not familar with this subject.
Please try backlight-rework branch of [1] together with Aaron's patches. [1] git://gitorious.org/jani/drm.git
OK, I started again with acpi_backlight=vendor and blacklist fujitsu-laptop. No visible change for me. Backlight still not working.
The acpi asl code shows that the backlight control is done in EC: Store (0x??, ^^^LPCB.EC0.BRIT) The fact that ACPI backlight control works seems to suggest that, maybe the PWM control circuit is on EC instead of GPU controller?
Jörg, the series was merged in 3.13 kernel. What is the status of your backlight with that?
2014-02-04 <bugzilla-daemon@bugzilla.kernel.org>: > https://bugzilla.kernel.org/show_bug.cgi?id=62281 > > --- Comment #16 from Jani Nikula <jani.nikula@intel.com> --- > Jörg, the series was merged in 3.13 kernel. What is the status of your > backlight with that? > > -- > You are receiving this mail because: > You reported the bug. No change, intel_backlight not working. I still use acpi. Jörg
New idea, please attach /sys/kernel/debug/dri/0/i915_opregion.
/sys/kernel/debug directory is empty. Do I need any special configuration options? Which?
sudo mount -t debugfs debugfs /sys/kernel/debug/
Created attachment 131901 [details] file /sys/kernel/debug/dri/0/i915_opregion
Finally progress. The VBT tells us the native PWM backlight should not be used or enabled in the first place. We have patches queued to fix this; please try current drm-intel-nightly branch of http://cgit.freedesktop.org/drm-intel without all the extra acpi/backlight related kernel parameters.
Nice work Jani, thanks for the VBT patches!
Now I have only acpi_backlight under /sys/class/backlight. Backlight works now. It's using acpi I presume.
(In reply to Aaron Lu from comment #23) > Nice work Jani, thanks for the VBT patches! Thanks, perhaps this helps in moving forward with defaulting to native backlight when available, without quirks! (In reply to jrg.otte from comment #24) > Now I have only acpi_backlight under /sys/class/backlight. > > Backlight works now. It's using acpi I presume. That's correct. Thanks for the report and testing. Fixed by these two commits in drm-intel-fixes, which will be queued for 3.15: commit d76fedf1980022912508e742660cebdc27c7a010 Author: Jani Nikula <jani.nikula@intel.com> Date: Wed Apr 9 11:22:06 2014 +0300 drm/i915: check VBT for supported backlight type commit 1901dd794a87911d82edab57dc6f87c7fe9c9bfc Author: Jani Nikula <jani.nikula@intel.com> Date: Wed Apr 9 11:31:37 2014 +0300 drm/i915: do not setup backlight if not available according to VBT