I did some more testing and I nailed the change to the 3.15.7 kernel update. I must have confused versions in my initial report.
Anyways, looking throught the changelog for that kernel version I found this changeset : commit be907c8468c9f47882036109ba550cd2748b86a0 Author: Alex Deucher <alexander.deuc...@amd.com> Date: Tue Jul 15 09:48:53 2014 -0400 drm/radeon: set default bl level to something reasonable commit 201bb62402e0227375c655446ea04fcd0acf7287 upstream. If the value in the scratch register is 0, set it to the max level. This fixes an issue where the console fb blanking code calls back into the backlight driver on unblank and then sets the backlight level to 0 after the driver has already set the mode and enabled the backlight. bugs: https://bugs.freedesktop.org/show_bug.cgi?id=81382 https://bugs.freedesktop.org/show_bug.cgi?id=70207 Signed-off-by: Alex Deucher <alexander.deuc...@amd.com> Tested-by: David Heidelberger <david.heidelber...@ixit.cz> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> This modified the way the radeon module handles default backlight values. Looking through the first bug report I found out about the "radeon.backlight" kernel option. Adding "radeon.backlight=0" to grub command line fixed the display brightness issue. ** Bug watch added: freedesktop.org Bugzilla #81382 https://bugs.freedesktop.org/show_bug.cgi?id=81382 ** Bug watch added: freedesktop.org Bugzilla #70207 https://bugs.freedesktop.org/show_bug.cgi?id=70207 ** Also affects: xserver-xorg-driver-radeonhd via https://bugs.freedesktop.org/show_bug.cgi?id=81382 Importance: Unknown Status: Unknown -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1363623 Title: [ASUS-A7K laptop] screen brightness dimmed after kernel update Status in xserver-xorg-driver-radeonhd: Unknown Status in “xorg” package in Ubuntu: New Bug description: Hello, Following the update from kernel version 3.13.0-34 to 3.13.0-35-generic the screen brightness got a lot dimmer. The Fn+F5/F6 control keys still work, in that the display gets dimmer and brighter, but the maximum brightness is too low. When starting ubuntu using the previous kernel release the display brightness is alright. I've looked around the web for ways to change the display brightness and I checked that both files "/sys/class/backlight/acpi_video0/brightness" and "/sys/class/backlight/radeon_bl0/brightness" have the maximum values, 15 and 255 respectively. The release I am running is : Ubuntu 14.04.1 LTS The XORG package version is : 1:7.7+1ubuntu8 Please feel free to contact me for any further information. ProblemType: Bug DistroRelease: Ubuntu 14.04 Package: xorg 1:7.7+1ubuntu8 ProcVersionSignature: Ubuntu 3.13.0-35.62-generic 3.13.11.6 Uname: Linux 3.13.0-35-generic x86_64 .tmp.unity.support.test.0: ApportVersion: 2.14.1-0ubuntu3.3 Architecture: amd64 CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins' CompositorRunning: None CurrentDesktop: GNOME Date: Sun Aug 31 11:40:07 2014 DistUpgraded: Fresh install DistroCodename: trusty DistroVariant: ubuntu ExtraDebuggingInterest: Yes, if not too technical GraphicsCard: Advanced Micro Devices, Inc. [AMD/ATI] RV630/M76 [Mobility Radeon HD 2600] [1002:9581] (prog-if 00 [VGA controller]) Subsystem: ASUSTeK Computer Inc. Device [1043:1562] InstallationDate: Installed on 2014-07-24 (38 days ago) InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417) MachineType: ASUSTeK Computer Inc. A7K ProcEnviron: TERM=xterm PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=fr_FR.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-35-generic root=/dev/mapper/vg_a7k-lv_root ro quiet splash vt.handoff=7 SourcePackage: xorg Symptom: display UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 07/25/2007 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: A7KAS.2 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: A7K dmi.board.vendor: ASUSTeK Computer Inc. dmi.board.version: 1.0 dmi.chassis.type: 10 dmi.chassis.vendor: ASUSTeK Computer Inc. dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrA7KAS.2:bd07/25/2007:svnASUSTeKComputerInc.:pnA7K:pvr1.0:rvnASUSTeKComputerInc.:rnA7K:rvr1.0:cvnASUSTeKComputerInc.:ct10:cvr: dmi.product.name: A7K dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK Computer Inc. version.compiz: compiz 1:0.9.11.2+14.04.20140714-0ubuntu1 version.ia32-libs: ia32-libs N/A version.libdrm2: libdrm2 2.4.52-1 version.libgl1-mesa-dri: libgl1-mesa-dri 10.1.3-0ubuntu0.1 version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A version.libgl1-mesa-glx: libgl1-mesa-glx 10.1.3-0ubuntu0.1 version.xserver-xorg-core: xserver-xorg-core 2:1.15.1-0ubuntu2 version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.8.2-1ubuntu2 version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.3.0-1ubuntu3.1 version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.910-0ubuntu1 version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.10-1ubuntu2 xserver.bootTime: Sun Aug 31 11:06:06 2014 xserver.configfile: default xserver.errors: xserver.logfile: /var/log/Xorg.0.log xserver.version: 2:1.15.1-0ubuntu2 xserver.video_driver: radeon To manage notifications about this bug go to: https://bugs.launchpad.net/xserver-xorg-driver-radeonhd/+bug/1363623/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp