On Thu, 03 Apr 2014, James Hogan <james@xxxxxxxxxxxxx> wrote: > Hi, > > I've noticed that v3.14 breaks the backlight on Dell XPS13. Reverting the > following commit fixes the issue for me (i.e. the GUI brightness controls work > again): > > bc0bb9fd1c78 drm/i915: remove QUIRK_NO_PCH_PWM_ENABLE > > It appears that in v3.14 (with the above patch): > * intel_backlight/brightness=4882 (max & default) causes > acpi_video0/brightness to have no effect. > * intel_backlight/brightness=0 causes acpi_video0/brightness to behave > corrrectly (the firmware (I assume) fades the brightness gradually when > acpi_video0/brightness is set) > * intel_backlight/brightness=something else in between often causes > acpi_video0 and intel_backlight to apparently "fight" over the backlight, > resulting in brightness flickering up and down every second or so. > > Reverting the above patch on v3.14: > * intel_backlight/brightness has no effect > * acpi_video0/brightness works normally > > It doesn't seem quite as simple as them trying to use the same hardware since > when intel_backlight/brightness=4882, acpi_video0/brightness has no effect at > all, so I don't really get what's going on. > > Can anybody shed some light or suggest a proper fix for this recurring issue? Tracked at https://bugs.freedesktop.org/show_bug.cgi?id=76276 BR, Jani. > > Thanks > James -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
