ThinkPad X220: unplugging DisplayPort breaks backlight (intel video)

[Marius Gedminas]

Steps to reproduce:

1. Plug in an external monitor using a DisplayPort -> HDMI cable
2. Unplug the cable

What happens about 30% of the time:

- Brightness of laptop's internal LCD drops to lowest level
- Brightness keys (Fn-Home/End on this Lenovo ThinkPad X220) produce the gnome-shell on-screen display of the changing brightness meter, but actual LCD brightness doesn't change.

There are a couple of workarounds:

1. Ctrl+Alt+F1 and use Fn-Home/End to control brightness, then Ctrl+Alt+F7 back to X (where brightness keys continue to not work)

or

2. Plug/unplug DisplayPort again, this usually fixes the brigthness (maybe 60% of the time)

I've been having this problem on this laptop since January of 2014. I was running Ubuntu 13.10 then, I'm running 14.04 now.

Sometimes the brightness-drop-and-you-can't-fix-it thing happens on DisplayPort hotplug rather than on unplug.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.13.0-37-generic 3.13.0-37.64
ProcVersionSignature: Ubuntu 3.13.0-37.64-generic 3.13.11.7
Uname: Linux 3.13.0-37-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.4
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: mg 3318 F.... pulseaudio
CurrentDesktop: GNOME
Date: Wed Oct 8 17:35:50 2014
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=bf592a79-5f4e-486d-b69d-7525d492dcc6
InstallationDate: Installed on 2012-07-25 (805 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
Lsusb:
 Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
 Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: LENOVO 4291WJF
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-37-generic root=UUID=36079681-53fc-4ca2-80ac-98321c07e8d2 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.13.0-37-generic N/A
 linux-backports-modules-3.13.0-37-generic N/A
 linux-firmware 1.127.7
RfKill:
 0: phy0: Wireless LAN
  Soft blocked: no
  Hard blocked: no
SourcePackage: linux
UpgradeStatus: Upgraded to trusty on 2014-04-18 (173 days ago)
dmi.bios.date: 07/18/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: 8DET69WW (1.39 )
dmi.board.asset.tag: Not Available
dmi.board.name: 4291WJF
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:bvr8DET69WW(1.39):bd07/18/2013:svnLENOVO:pn4291WJF:pvrThinkPadX220:rvnLENOVO:rn4291WJF:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 4291WJF
dmi.product.version: ThinkPad X220
dmi.sys.vendor: LENOVO

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.17 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.17-utopic/

[Brad Figg (brad-figg)]

This change was made by a bot.

[Marius Gedminas (mgedmin)]

With kernel 3.17.0-031700-generic:

- 1st time I plugged in the DisplayPort connector, nothing happened (bug 1263681). I pressed Fn-Home as a workaround and external monitor got detected, but internal monitor went black (no picture, no backlight). Pressing Fn-Home again turned it on, at minimum brightness. Fn-Home/End brightness control keys continue to work.

- 1st unplug changed nothing

- 2nd hotplug was detected instantly, internal LCD went black again. Fn-Home was required again to bring it to life.

- 2nd unplug changed nothing

- 3rd hotplug was same as 2nd.

I can bring the internal LCD into the no-picture-no-backlight state by pressing Fn-End until I reach minimum brigthness. This is something new: with older kernel versions minimum brightness still had a visible picture.

Conclusion: latest kernel has one half of the bug (DP hotplugging drops screen brightness to minimum level) but so far hasn't shown the other half (brightness keys don't stop working).

[penalvch (penalvch)]

Marius Gedminas, did this problem not occur in a release prior to 13.10?

[Marius Gedminas (mgedmin)]

I did not have a DisplayPort cable before January 2014.

Plugging/unplugging VGA never caused any brightness issues. And still doesn't -- I just tested with current 14.04 kernel (had to go back to it because I need VirtualBox for work).

[penalvch (penalvch)]

Marius Gedminas, the issue you are reporting is an upstream one. Could you please report this problem through the appropriate channel by following the instructions _verbatim_ at https://wiki.ubuntu.com/Bugs/Upstream/kernel ?

Please provide a direct URL to your e-mail to the mailing list once you have made it so that it may be tracked.

Thank you for your understanding.

[Marius Gedminas (mgedmin)]

For the record I haven't experienced this bug since upgrading to Ubuntu 14.10 (on release day, i.e. the 24th of October, 2014).

[penalvch (penalvch)]

Marius Gedminas, this bug report is being closed due to your last comment https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1378863/comments/8 regarding this being fixed with an update. For future reference you can manage the status of your own bugs by clicking on the current status in the yellow line and then choosing a new status in the revealed drop down box. You can learn more about bug statuses at https://wiki.ubuntu.com/Bugs/Status. Thank you again for taking the time to report this bug and helping to make Ubuntu better. Please submit any future bugs you may find.