Bug 83460 - [radeon regression] Backlight turned off since kernel upgrade
Summary: [radeon regression] Backlight turned off since kernel upgrade
Status: RESOLVED FIXED
Alias: None
Product: DRI
Classification: Unclassified
Component: DRM/Radeon (show other bugs)
Version: XOrg git
Hardware: x86-64 (AMD64) Linux (All)
: medium normal
Assignee: Default DRI bug account
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Reported: 2014-09-03 21:38 UTC by Gregory Lardiere
Modified: 2014-09-29 18:52 UTC (History)
1 user (show)

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Description Gregory Lardiere 2014-09-03 21:38:08 UTC 
Since the upgrade to Ubuntu kernel 3.13.0-35 (from 3.13.0-34), the screen is very dark to the point it's unusable.
Backlight seems completely turned off. Using the brightness keys doesn't help.
It was working fine with 3.13.0-34.
I found that the offending patch is "drm/radeon: set default bl level to something reasonable".
I reverted this patch and recompiled 3.13.0-35, and it solved the problem.
I also checked that this problem also affects mainline kernel 3.17rc3.
More technical details can be found on Ubuntu's bugtracker : https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1364148
Comment 1 Gregory Lardiere 2014-09-29 18:52:02 UTC 
Fixed in kernel 3.17rc7.
More informations here : https://bugs.freedesktop.org/show_bug.cgi?id=81382

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