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This happens on my X220, running trusty, linux 3.13.0-24-generic. It's
the exact same problem discussed on
https://bugzilla.redhat.com/show_bug.cgi?id=1067071. Discussed also on
kernel mailing list: https://lkml.org/lkml/2014/2/19/720. It worked on
3.12, and upstream acknowledges the regression.
To reproduce, remove the X220 from the dock. The brightness is set to
minimum (the screen is nearly unreadable) and the brightness control is
broken, you can't adjust it by hardware keys.
My hardware:
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core
Processor Family Integrated Graphics Controller (rev 09) (prog-if 00 [VGA
controller])
Subsystem: Lenovo Device 21da
Kernel driver in use: i915
Docked on a ThinkPad mini dock series 3.
I have nothing much relevant in /var/log/syslog. Below there are
excerpts of it when brightness is working:
Apr 16 14:55:37 galactica kernel: [79261.217384] [drm:asle_set_backlight], bclp
= 0x800000ff
Apr 16 14:55:37 galactica kernel: [79261.217390] [drm:asle_set_backlight],
updating opregion backlight 255/255
Apr 16 14:55:37 galactica kernel: [79261.217394]
[drm:intel_panel_get_max_backlight], max backlight PWM = 4648
Apr 16 14:55:37 galactica kernel: [79261.217396]
[drm:intel_panel_actually_set_backlight], set backlight PWM = 4590
Apr 16 14:55:37 galactica kernel: [79261.217537] [drm:asle_set_pwm_freq], PWM
freq is not supported
And brightness not working:
Apr 16 15:23:46 galactica kernel: [80948.263160] [drm:asle_set_backlight], bclp
= 0x80000058
Apr 16 15:23:46 galactica kernel: [80948.263168] [drm:asle_set_pwm_freq], PWM
freq is not supported
Apr 16 15:23:46 galactica kernel: [80948.280637] [drm:asle_set_backlight], bclp
= 0x80000041
Apr 16 15:23:46 galactica kernel: [80948.280642] [drm:asle_set_pwm_freq], PWM
freq is not supported
A workaround is to echo values directly to
/sys/class/backlight/intel_backlight/brightness. Maximum brightness is 4648
(/sys/class/backlight/intel_backlight/max_brightness).
e.g.: # echo 500 > /sys/class/backlight/intel_backlight/brightness
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.13.0-24-generic 3.13.0-24.46
ProcVersionSignature: Ubuntu 3.13.0-24.46-generic 3.13.9
Uname: Linux 3.13.0-24-generic i686
ApportVersion: 2.14.1-0ubuntu2
Architecture: i386
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC1: ursula 3881 F.... pulseaudio
/dev/snd/controlC0: ursula 3881 F.... pulseaudio
CurrentDesktop: Unity
Date: Wed Apr 16 15:09:23 2014
HibernationDevice: RESUME=UUID=68890e28-0eee-4184-9456-cc267c4a5f31
InstallationDate: Installed on 2013-05-27 (323 days ago)
InstallationMedia: Ubuntu 12.04.2 LTS "Precise Pangolin" - Release i386
(20130213)
MachineType: LENOVO 4286CTO
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-24-generic
root=UUID=4db5451d-c250-47bc-9c4e-235fb1967ee5 ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-3.13.0-24-generic N/A
linux-backports-modules-3.13.0-24-generic N/A
linux-firmware 1.127
SourcePackage: linux
UpgradeStatus: Upgraded to trusty on 2013-11-04 (162 days ago)
dmi.bios.date: 12/01/2011
dmi.bios.vendor: LENOVO
dmi.bios.version: 8DET56WW (1.26 )
dmi.board.asset.tag: Not Available
dmi.board.name: 4286CTO
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias:
dmi:bvnLENOVO:bvr8DET56WW(1.26):bd12/01/2011:svnLENOVO:pn4286CTO:pvrThinkPadX220:rvnLENOVO:rn4286CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 4286CTO
dmi.product.version: ThinkPad X220
dmi.sys.vendor: LENOVO
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Invalid
** Tags: apport-bug bios-outdated-1.39 i386 kernel-da-key trusty
--
[Lenovo ThinkPad X220] kernel 3.13 i915 brightness settings broken when going
from docked -> undocked
https://bugs.launchpad.net/bugs/1308674
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