Bug 83460

Summary:	[radeon regression] Backlight turned off since kernel upgrade
Product:	DRI	Reporter:	Gregory Lardiere <spmf2004-freedesktop>
Component:	DRM/Radeon	Assignee:	Default DRI bug account <dri-devel>
Status:	RESOLVED FIXED	QA Contact:
Severity:	normal
Priority:	medium	CC:	matt2566
Version:	XOrg git
Hardware:	x86-64 (AMD64)
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:

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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