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[Peteryuchuang <1554613@xxxxxxxxxxxxxxxxxx>]

(In reply to nhellwege from comment #43)
> (In reply to tranceash from comment #38)
> > looks like a power management issues dating 8 months back, Also happened on
> > the broadwell systems https://bugs.freedesktop.org/show_bug.cgi?id=91393.
> > This makes any linux system a pain to work because of this integrated gpu
> > driver . Skylake has been out for 7 months and we still have problems
> 
> I am starting to believe that the common error 
> 
>  [drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe A
> FIFO underrun
> 
> is not actually responsible for the flicker. To be more precise, the FIFO
> underrun may result in conjunction with a flicker, but is not a unique
> indication. I am currently bisecting the kernel and right now I am on commit
> 5ffd4da+. This commit does show the FIFO underun but not at the same time
> the screen turns completely black for a split second. 
> 
> I assume the flicker (screen completely black for a split second) is not
> directly mapped by the FIFO underrun. 
> 
> Reading https://bugs.freedesktop.org/show_bug.cgi?id=91393, I think our bug
> is at least related, if not identical.

I tend to agree with you that the error

[drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe A
FIFO underrun

may not be specific to the problem we are talking about here.

Regarding my previous comment on whether the laptop is plugged into AC,
Thomas is right: if I wait long enough, the flicker does occur even when
plugged in, although much less frequent on my machine.

Interestingly, now that I am plugged into AC, the CPU pipe A FIFO
underrun thing is no longer the error I see. Instead, this is the error
I saw on dmesg:

[ 2045.481992] [drm:intel_pipe_update_end [i915]] *ERROR* Atomic update
failure on pipe A (start=84070 end=84071) time 9 us, min 1073, max 1079,
scanline start 1087, end 1079

This is the first time I see this error since I started looking for the
solution for this problem.

Hope this might give you some clues.

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https://bugs.launchpad.net/bugs/1554613

Title:
  screen flickering on XPS13 9350

Status in Linux:
  Incomplete
Status in linux package in Ubuntu:
  Triaged

Bug description:
  see LP: #1552304

  does not affect 4.4.0-8
  affects 4.4.0-9 to 4.4.0-16

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: linux-image-generic 4.4.0.11.12
  ProcVersionSignature: Ubuntu 4.4.0-8.23-generic 4.4.2
  Uname: Linux 4.4.0-8-generic x86_64
  ApportVersion: 2.20-0ubuntu3
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  tbonfort   1498 F.... pulseaudio
  CurrentDesktop: KDE
  Date: Tue Mar  8 09:57:12 2016
  HibernationDevice: RESUME=UUID=3248e0d7-0dac-4ccc-8982-b5ac5ce6ed5e
  InstallationDate: Installed on 2016-01-07 (61 days ago)
  InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
  Lsusb:
   Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
   Bus 001 Device 003: ID 0c45:670c Microdia
   Bus 001 Device 002: ID 0a5c:6412 Broadcom Corp.
   Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
  MachineType: Dell Inc. XPS 13 9350
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-8-generic root=UUID=757547b8-d0e4-4eb8-8afd-920b743f99a4 ro quiet splash vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-4.4.0-8-generic N/A
   linux-backports-modules-4.4.0-8-generic  N/A
   linux-firmware                           1.156
  SourcePackage: linux
  UpgradeStatus: Upgraded to xenial on 2016-02-28 (9 days ago)
  dmi.bios.date: 01/08/2016
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: 1.2.3
  dmi.board.name: 07TYC2
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A01
  dmi.chassis.type: 9
  dmi.chassis.vendor: Dell Inc.
  dmi.modalias: dmi:bvnDellInc.:bvr1.2.3:bd01/08/2016:svnDellInc.:pnXPS139350:pvr:rvnDellInc.:rn07TYC2:rvrA01:cvnDellInc.:ct9:cvr:
  dmi.product.name: XPS 13 9350
  dmi.sys.vendor: Dell Inc.

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