touch-packages team mailing list archive

[Mika-kahola <1522922@xxxxxxxxxxxxxxxxxx>]

Created attachment 120893
DP debugging

Tom, I would bother you again to provide some debugging info. From the
dmesg you sent it seems that you are experiencing a lot of hpd
interrupts. When that happens the driver checks if the DP channel
equalization is still ok. On your case, channel equalization is not ok
yielding DP link to be retrained. Of course, this causes flickering as
the DP link is broken for some time. The patch I'm proposing for
debugging purposes applies on top of the latest -nightly and on top of
these previous patches

https://patchwork.freedesktop.org/patch/69394/
https://patchwork.freedesktop.org/patch/69395/
https://patchwork.freedesktop.org/patch/69396/

The patch adds more verbose debug information on channel equalization
and limits the DP link retraining to 5. After 5 attempts to retrain the
link you probably end up having a non-flickering display or a black
screen. Please, report back with dmesg.

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https://bugs.launchpad.net/bugs/1522922

Title:
  Screen flickering in Intel i915 driver

Status in Nouveau Xorg driver:
  Incomplete
Status in libdrm package in Ubuntu:
  Confirmed

Bug description:
  There's an upstream bug reported here
  https://bugs.freedesktop.org/show_bug.cgi?id=91393 that causes screen
  flickering when using the Intel i915 builtin driver (at resolutions
  lower than the maximal one).

  I think that it will be fixed in newer kernel versions, but for the
  time being, as reported here
  https://bugs.freedesktop.org/show_bug.cgi?id=91393#c25 (and as
  personally tested) reverting those two commits fixes the problem.

  Would that be possible to release a fixed version for the 4.2.0
  stream?

  ProblemType: Bug
  DistroRelease: Ubuntu 15.10
  Package: linux-image-4.2.0-19-generic 4.2.0-19.23
  ProcVersionSignature: Ubuntu 4.2.0-19.23-generic 4.2.6
  Uname: Linux 4.2.0-19-generic x86_64
  ApportVersion: 2.19.1-0ubuntu5
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  bettini    1378 F.... pulseaudio
   /dev/snd/controlC1:  bettini    1378 F.... pulseaudio
  CurrentDesktop: KDE
  Date: Fri Dec  4 19:01:00 2015
  HibernationDevice: RESUME=UUID=7ddbc972-3ad6-40de-9313-2bb9395145f9
  InstallationDate: Installed on 2015-05-08 (210 days ago)
  InstallationMedia: Kubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
  MachineType: Dell Inc. Dell Precision M3800
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-19-generic root=UUID=dd2c7064-53b9-4720-96ab-5e8a3f2db3ea ro noprompt quiet splash vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-4.2.0-19-generic N/A
   linux-backports-modules-4.2.0-19-generic  N/A
   linux-firmware                            1.149.3
  SourcePackage: linux
  UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
  UpgradeStatus: Upgraded to wily on 2015-11-07 (26 days ago)
  dmi.bios.date: 08/17/2015
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A10
  dmi.board.name: Dell Precision M3800
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A10
  dmi.chassis.type: 8
  dmi.chassis.vendor: Dell Inc.
  dmi.chassis.version: Not Specified
  dmi.modalias: dmi:bvnDellInc.:bvrA10:bd08/17/2015:svnDellInc.:pnDellPrecisionM3800:pvrA10:rvnDellInc.:rnDellPrecisionM3800:rvrA10:cvnDellInc.:ct8:cvrNotSpecified:
  dmi.product.name: Dell Precision M3800
  dmi.product.version: A10
  dmi.sys.vendor: Dell Inc.

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