Display corruption with Lenovo T450 and external monitors

[Cs-gon]

We are experiencing frequent display corruption and flickering when using Lenovo T450 notebooks with the Lenovo Pro-/Ultra-Docks when external monitors are connected.

We first experienced these problems when upgrading 16.04 systems to the HWE stack. The systems are using the integrated Intel graphics card (i915 kernel module) and the modesetting Xorg driver. The problems are mostly appearing when the monitors are woken up from standby (e.g. after coming back from lunch break), or when the system was suspended and is resumed. But we also have reports from users, that experience those problems during normal work, but I couldn't verify this myself yet.

Sometimes removing the system from the dock and re-docking it fixes the problem temporarily, but not always.

I will attach videos which show the problem.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xserver-xorg-core-hwe-16.04 2:1.19.6-1ubuntu4.1~16.04.2
ProcVersionSignature: Ubuntu 4.15.0-34.37lvm6-generic 4.15.18
Uname: Linux 4.15.0-34-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Apr 11 18:12:00 2019
SourcePackage: xorg-server-hwe-16.04
UpgradeStatus: No upgrade log present (probably fresh install)

[Cs-gon (cs-gon)]

first video

[Cs-gon (cs-gon)]

second video

[Cs-gon (cs-gon)]

I have also opened the following upstream bugreport: https://gitlab.freedesktop.org/xorg/xserver/issues/683

[Timo Aaltonen (tjaalton)]

16.04 is EOL, if you can reproduce on a newer release, please open a new bug, thanks