No signal to external monitor after [drm:intel_pch_fifo_underrun_irq_handler [i915]] *ERROR* PCH transcoder B FIFO underrun

[Karl Kastner]

Since recently, my external monitor goes black in random intervals of 5-10 min.

I have Dell monitor connected via display port to a Lenovo ThinkPad T510. I always switch off the laptop screen with "xrandr -q --output LVDS-1 --off" and work only with the external monitor. This combination worked flawlessly for the last six month.

Since a couple of days, the laptop suddenly stops sending a signal to the external monitor, which goes black. The signal is send again, after replugging the display port cable or repowering the monitor. The problem does not seem to occur when I do not switch off the laptop monitor and work on two screens in parallel.

At first I thought it was a problem of the monitor, but it seems to be a bug in the graphics driver:

[29042.368884] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun
[29042.368948] [drm:intel_pch_fifo_underrun_irq_handler [i915]] *ERROR* PCH transcoder B FIFO underrun
[29049.759513] [drm:intel_pch_fifo_underrun_irq_handler [i915]] *ERROR* PCH transcoder B FIFO underrun
[29050.354467] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to get link status
[29050.441402] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to start channel equalization
[29050.526209] [drm:intel_pch_fifo_underrun_irq_handler [i915]] *ERROR* PCH transcoder B FIFO underrun

Note, over the last years I frequently (say at least on a weekly basis) observed that the external monitor goes black for the flash of a second but then instantly recovers. This happened with combinations of different laptops and screens. I thought so far this was related to fluctuations in the power supply, but maybe there is something more sinister at hand.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xserver-xorg-video-intel 2:2.99.917+git20171229-1
ProcVersionSignature: Ubuntu 4.10.0-42.46-generic 4.10.17
Uname: Linux 4.10.0-42-generic x86_64
.tmp.unity_support_test.0:

ApportVersion: 2.20.9-0ubuntu7.10
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell]
CompositorRunning: None
CurrentDesktop: GNOME
Date: Fri Feb 28 10:36:40 2020
DistUpgraded: 2018-05-24 16:40:32,746 DEBUG failed to SystemUnLock() (E:Not locked)
DistroCodename: bionic
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes
GraphicsCard:
 Intel Corporation Core Processor Integrated Graphics Controller [8086:0046] (rev 02) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Core Processor Integrated Graphics Controller [17aa:215a]
InstallationDate: Installed on 2015-11-05 (1575 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
MachineType: LENOVO 4384WRP
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.10.0-42-generic root=UUID=3949412b-a319-496c-8e0a-8b24db59326e ro uveau.modeset=0 acpi_enforce_resources=lax nosplash uveau.modeset=0 acpi_enforce_resources=lax acpi_enforce_resources=lax acpi_enforce_resources=lax acpi_enforce_resources=lax acpi_enforce_resources=lax acpi_enforce_resources=lax
SourcePackage: xserver-xorg-video-intel
UpgradeStatus: Upgraded to bionic on 2018-05-24 (644 days ago)
dmi.bios.date: 09/26/2012
dmi.bios.vendor: LENOVO
dmi.bios.version: 6MET92WW (1.52 )
dmi.board.name: 4384WRP
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:bvr6MET92WW(1.52):bd09/26/2012:svnLENOVO:pn4384WRP:pvrThinkPadT510:rvnLENOVO:rn4384WRP:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 4384WRP
dmi.product.version: ThinkPad T510
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.13.1+18.04.20180302-0ubuntu1
version.libdrm2: libdrm2 2.4.99-1ubuntu1~18.04.2
version.libgl1-mesa-dri: libgl1-mesa-dri 19.2.8-0ubuntu0~18.04.2
version.libgl1-mesa-glx: libgl1-mesa-glx 19.2.8-0ubuntu0~18.04.2
version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4.4
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.5-1ubuntu1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20171229-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2
xserver.bootTime: Thu Feb 27 09:46:06 2020
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.19.6-1ubuntu4.4
xserver.video_driver: modeset