Created attachment 98965 [details] dmesg with drm.debug=0xe Similar to https://bugs.freedesktop.org/show_bug.cgi?id=76276. Since kernel 3.14.1 backlight control doesn't work on Dell XPS M1330 unless I do: # echo 255000 > /sys/class/backlight/intel_backlight to temporarily fix it. As requested in https://bugs.freedesktop.org/show_bug.cgi?id=76276#c41 I have attached dmesg with drm.debug=0xe and /sys/kernel/debug/dri/0/i915_opregion. I produced these on 3.15-rc5.
Created attachment 98966 [details] i915_opregion
I finally got some time to do a bit of debugging. Applying this hack: https://bugs.freedesktop.org/show_bug.cgi?id=76276#c15 and only this (to 3.15-rc6) solves the problem for me.
(In reply to comment #2) > I finally got some time to do a bit of debugging. > > Applying this hack: https://bugs.freedesktop.org/show_bug.cgi?id=76276#c15 > and only this (to 3.15-rc6) solves the problem for me. And backlight control works with that? What do you have in /sys/class/backlight? The VBT says we should register backlight for that, but then it doesn't work. Hmm.
(In reply to comment #3) > (In reply to comment #2) > > I finally got some time to do a bit of debugging. > > > > Applying this hack: https://bugs.freedesktop.org/show_bug.cgi?id=76276#c15 > > and only this (to 3.15-rc6) solves the problem for me. > > And backlight control works with that? What do you have in > /sys/class/backlight? > > The VBT says we should register backlight for that, but then it doesn't > work. Hmm. Yeah I don't have intel_backlight there. with kernel 3.15-rc6 and the hack applied I have: $ ls -l /sys/class/backlight/ total 0 lrwxrwxrwx 1 root root 0 May 27 16:42 acpi_video0 -> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video0 With kernel 3.13.8 (before regression) I have: $ ls -l total 0 lrwxrwxrwx 1 root root 0 May 27 16:44 acpi_video0 -> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video0 lrwxrwxrwx 1 root root 0 May 27 16:44 intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight Backlight control (Fn+ArrowUp/Down) works on both of those setups, but it breaks when the 3.15-rc6+hack kernel is suspended and woken up again. Do you need any other infomation?
Please attach intel_reg_dumper output for the working and non-working kernels, with no hacks applied and no workarounds (echo or backlight change) done. Intel_reg_dumper is part of intel-gpu-tools: http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/
Created attachment 99960 [details] intel_reg_dumper for kernel 3.13.8
Created attachment 99961 [details] intel_reg_dumper for kernel 3.15.0-rc7
I have been running 3.13.8 for the past two months and haven't tested any later kernels other than what I did back in May. I now updated to 3.16.1 and this bug has clearly been resolved at some point. Thanks!
Issue still exists , tested in relese 14 ,on 11/11/15
(In reply to Jaya from comment #9) > Issue still exists , tested in relese 14 ,on 11/11/15 No idea what "relese 14" might refer to. Clearly the original reporter here had an issue that was fixed along the way, so let's keep this one closed. Please file a new bug for your issue.
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