Lenovo T480: problem with external screens

[Adrian]

Setup: two external screens connected through separate DP ports and a docking station to a laptop Lenovo T480

When the laptop is launched in the docking station (lid is closed) the screens remain off (there is information about missing signal).
When the laptop is launched out of docking station (using only the internal screen), after logging to the Gnome session, connecting to the docking station: there is an image on two external screens. However, once the laptop is suspended or screensaver enabled (switch off all screens), after wakeup, all screens remain off.

This bug is 4.15.0-44 kernel specific. With the previous version 4.15.0-43 the external screens were served properly.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-44-generic 4.15.0-44.47
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
Uname: Linux 4.15.0-43-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: afiergol 9976 F.... pulseaudio
 /dev/snd/pcmC0D0p: afiergol 9976 F...m pulseaudio
 /dev/snd/controlC0: afiergol 9976 F.... pulseaudio
CurrentDesktop: GNOME
Date: Wed Jan 30 17:27:50 2019
HibernationDevice: RESUME=UUID=7b4a9d17-f6d7-42ed-8f12-34f46c41cc6c
InstallationDate: Installed on 2018-04-05 (300 days ago)
InstallationMedia: Ubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
MachineType: LENOVO 20L6S04200
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-43-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash nogpumanager intel_iommu=on,igfx_off iommu=pt kvm.ignore_msrs=1
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-43-generic N/A
 linux-backports-modules-4.15.0-43-generic N/A
 linux-firmware 1.173.3
SourcePackage: linux
UpgradeStatus: Upgraded to bionic on 2018-08-22 (161 days ago)
dmi.bios.date: 11/07/2018
dmi.bios.vendor: LENOVO
dmi.bios.version: N24ET44W (1.19 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20L6S04200
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias: dmi:bvnLENOVO:bvrN24ET44W(1.19):bd11/07/2018:svnLENOVO:pn20L6S04200:pvrThinkPadT480:rvnLENOVO:rn20L6S04200:rvrNotDefined:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad T480
dmi.product.name: 20L6S04200
dmi.product.version: ThinkPad T480
dmi.sys.vendor: LENOVO

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[MaskedDriver (maskeddriver)]

I'm having the same issue on a Dell Latitude 5289 laptop connected to a dell USB-C dock with 2 external monitors, and USB keyboard and mouse (Razer Naga Chroma).

My computer will immediately lock up upon pressing Super + L to lock the screen when it's connected to the dock. When disconnected from the dock, it wakes up fine.

This is isolated to 4.15.0-44 for me as well. I am unable to replicate in 4.15.0-43.

[MaskedDriver (maskeddriver)]

Related issues:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1813956
https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1813738
https://bugs.launchpad.net/ubuntu/+source/linux-signed/+bug/1813902