On 2010.05.23 12:11:28 +0200, Johannes Schauer wrote:
> hi!
> 
> on newer kernels, whenever i modprobe i915 my screen goes black. the
> backlight is still on and the machine continues working but now as a
> headless system.
> 
> by bisection i found the commit that introduced this regression:
> 
> 885a5fb5b120a5c7e0b3baad7b0feb5a89f76c18 is the first bad commit
> commit 885a5fb5b120a5c7e0b3baad7b0feb5a89f76c18
> Author: Zhenyu Wang <zhenyuw@linux.intel.com>
> Date:   Tue Jan 12 05:38:31 2010 +0800
> 
>     drm/i915: fix pixel color depth setting on eDP
> 
>     Original DP mode_valid check didn't take pixel color depth into account,
>     which made one 1600x900 eDP panel's mode check invalid because of
> overclock,
>     but actually this 6bpc panel does can work with x1 lane at 2.7G.
> This one
>     trys to take bpp value properly both in mode validation and mode
> setting.
> 
>     Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
>     Signed-off-by: Eric Anholt <eric@anholt.net>
> 
> :040000 040000 3c99ae05b82db5b8e453d2062bcf56743794476b
> d7e0aa843fe4f8173f624572c77a7fe93b6fc455 M      drivers
> 
> 
> this issue appears on my dell e6510 with intel hd (arrandale) and one
> can find many bugreports about the same effect on the e6410 and thinkpad
> x200s - all using said platform:
> 
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/554569
> https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/561802
> 
> i also can confirm, that when removing the changes from this commit in
> the most recent intel_dp.c then my display even works on 2.6.34 :)
> 

Can you send me kernel boot dmesg with drm.debug=7, intel_reg_dump and
VBIOS image dump? Better if you could file a new bug to fd.o, in case
your eDP panel issue is different from #28070.


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