[Bug 1939222] Re: DisplayPort over USB-C not working after release update

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: ubuntu-release-upgrader (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1939222

Title:
  DisplayPort over USB-C not working after release update

Status in ubuntu-release-upgrader package in Ubuntu:
  Confirmed

Bug description:
  After (automated) update from 5.8.0-63 to 5.11.0.-25 the displayport over usb-c (Thinkpad e15gen2 i5-1135G7 / GeForce MX450/PCIe/SSE2) is not working properly.
  Revert to 5.8.0-63 resolves the problem.
  The problem is independent of nvdia-drivers (tried 470, 460 and intel only  drivers). Same Monitors connected over HDMI work properly. Problem is limited to displayport over usb-c.

  Problem symptoms: Monitor atttached over displayport allows only VGA resolution(1024 * 768)  and
  flickers (on/off periodically). 

  no special error messages found in dmesg except for abundance of
  "i915 0000:00:02.0: [drm] *ERROR* failed to enable link training"

  ProblemType: Bug
  DistroRelease: Ubuntu 20.04
  Package: ubuntu-release-upgrader-core 1:20.04.35
  ProcVersionSignature: Ubuntu 5.11.0-25.27~20.04.1-generic 5.11.22
  Uname: Linux 5.11.0-25-generic x86_64
  NonfreeKernelModules: nvidia_modeset nvidia
  ApportVersion: 2.20.11-0ubuntu27.18
  Architecture: amd64
  CasperMD5CheckResult: skip
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  Date: Sun Aug  8 09:12:10 2021
  InstallationDate: Installed on 2021-06-14 (54 days ago)
  InstallationMedia: Ubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
  PackageArchitecture: all
  ProcEnviron:
   LANGUAGE=en_IL:en
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_IL
   SHELL=/bin/bash
  SourcePackage: ubuntu-release-upgrader
  Symptom: release-upgrade
  UpgradeStatus: No upgrade log present (probably fresh install)
  VarLogDistupgradeTermlog:

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