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[Bug 1568865] Re: [drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe B FIFO underrun


@shinyblue (and others) would you be able to try the 4.6.0-rc6 kernel?
It looks like some new commits relating to i915 have been made since


drm/i915: Use fw_domains_put_with_fifo() on HSW	
drm/i915: Force ringbuffers to not be at offset 0	-2/+5
drm/i915: Adjust size of PIPE_CONTROL used for gen8 render seqno write
drm/i915/skl: Fix spurious gpu hang with gt3/gt4 revs
drm/i915/skl: Fix rc6 based gpu/system hang
drm/i915/userptr: Hold mmref whilst calling get-user-pages
drm/i915: Fixup the free space logic in ring_prepare
drm/i915/skl+: Use plane size for relative data rate calculation

I'm assuming if you install a recent kernel you don't get the i915_bpo
module (Ubuntu's backported version of i915, not sure from when/where) ?

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

Status in linux package in Ubuntu:

Bug description:
  Running Gnome-Shell on ubuntu 16.04 on my Dell XPS 15 9550 laptop
  using Intel graphics (Nvidia card turned off), I get this error in
  syslog when plugging in an external monitor (HDMI).

  Apr 11 14:28:38 miaco kernel: [ 2616.604641]
  [drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe
  B FIFO underrun

  Meanwhile both screens flash and show corruption. Most of the time
  this has caused a hang that needs a hard power off to get out of, but
  occasionally removing the external monitor is enough to get going
  again and so I've been able to find this message in the logs.

  Note that when using Nvidia (proprietary) drivers and Unity DE I do
  not have this problem; so it seems to be related to the intel drivers,
  or possibly Gnome Shell's use of them.

  Happy to help if I can (would like to be able to use external


  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: linux-image-4.4.0-18-generic 4.4.0-18.34
  ProcVersionSignature: Ubuntu 4.4.0-18.34-generic 4.4.6
  Uname: Linux 4.4.0-18-generic x86_64
  ApportVersion: 2.20.1-0ubuntu1
  Architecture: amd64
   /dev/snd/controlC0:  rich       1943 F.... pulseaudio
  Date: Mon Apr 11 14:31:26 2016
  InstallationDate: Installed on 2016-03-21 (21 days ago)
  InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160307)
   Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
   Bus 001 Device 003: ID 04f3:21d5 Elan Microelectronics Corp. 
   Bus 001 Device 002: ID 0a5c:6410 Broadcom Corp. 
   Bus 001 Device 004: ID 0c45:6713 Microdia 
   Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
  MachineType: Dell Inc. XPS 15 9550
   PATH=(custom, no user)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-18-generic.efi.signed root=UUID=3f8391d5-e9cc-4768-8efb-8f04d340567c ro quiet splash vt.handoff=7
   Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not accessible: Permission denied
   No PulseAudio daemon running, or not running as session daemon.
   linux-restricted-modules-4.4.0-18-generic N/A
   linux-backports-modules-4.4.0-18-generic  N/A
   linux-firmware                            1.157
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 01/25/2016
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: 01.01.19
  dmi.board.name: 0N7TVV
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A00
  dmi.chassis.type: 9
  dmi.chassis.vendor: Dell Inc.
  dmi.modalias: dmi:bvnDellInc.:bvr01.01.19:bd01/25/2016:svnDellInc.:pnXPS159550:pvr:rvnDellInc.:rn0N7TVV:rvrA00:cvnDellInc.:ct9:cvr:
  dmi.product.name: XPS 15 9550
  dmi.sys.vendor: Dell Inc.

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