Bug 26202

Summary: After upgrade to 2.6.37: display backlight is not controllable after first dpms dim
Product: Drivers Reporter: Jens Weibler (bugzilla-kernel)
Component: Video(DRI - Intel)Assignee: drivers_video-dri-intel (drivers_video-dri-intel)
Severity: high CC: florian, indan, maciej.rutecki, rjw
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 2.6.37 Subsystem:
Regression: Yes Bisected commit-id:
Bug Depends on:    
Bug Blocks: 21782    
Attachments: Print more debugging info

Description Jens Weibler 2011-01-06 10:06:59 UTC
I just upgraded to 2.6.37 (from http://kernel.ubuntu.com/~kernel-ppa/mainline/v2.6.37-natty/) and my display backlight can't be controlled any more after it's dimmed (dpms?).

It works just fine after booting with boot keys (Fn+Cursor Up/Down) and KDE Power Management Panel (Battery Settings - Screen Brightness Slider).

Both /sys/class/backlight/acpi_video0/(actual_brightness|brightness) return the current value. Setting acpi_video0/brightness shows no effect other than a changed value of actual_brightness and brightness.

Dell Latitude E6500
Intel GM45
Comment 1 Jens Weibler 2011-01-06 10:15:25 UTC
Just tested it: xset dpms force standy triggers it
I've attached my kern.log with drm.debug=0x07
Comment 2 Jens Weibler 2011-01-06 10:18:09 UTC
Uploadsize too small ;)
75MB bzipped to 2MB but I can only upload 1MB
Comment 3 Indan 2011-01-11 02:50:31 UTC
Created attachment 43232 [details]
Print more debugging info

Your attachment didn't make it.

Can you try this debugging patch and without drm.debug and post the result? (Or just drm.debug=0x02.) This is just to see if setting and getting the backlight works as it's suposed to.
Comment 4 Jens Weibler 2011-01-28 10:38:51 UTC
Seems to be fixed in 2.6.38 rc2