Scrambled pixels in blocks with lenovo dock gen 2 thunderbolt 3 DP 1.4

Bug #1902522 reported by Fodor Zoltan on 2020-11-02
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
nvidia-graphics-drivers-450 (Ubuntu)
Undecided
Unassigned

Bug Description

I am experiencing issues with rendering on 1440p@165hz in Ubuntu 20.04 with Lenovo Dock Gen 2 thunderbolt 3 40AN through DP 1.4. Depending on what is rendered and mouse position the screen can get blocks of scrambled purple pixels. These blocks are always horizontally half of the screen either on the right or the left and they are variable in height. Also the display sometimes flickers / disconnects. This configuration works correctly on Windows 10.

Strange part is that this mostly happens during browsing websites, especially when scrolling or typing / moving mouse in certain positions. Using Intelij IDE it doesn't happen. Watching youtube fullscreen even 8K at 60fps it works normally.

Picture of the artifact: https://forums.lenovo.com/download/228570
Video of the artifact: https://youtu.be/FnTWpv90DjE

Ubuntu: Ubuntu 20.04.1 LTS
System: Linux archy-Lenovo-Legion-7-15IMHg05 5.9.2-050902-generic #202010290646 SMP Thu Oct 29 11:11:09 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Dock firmware: trdockfw3167
Nvidia driver: nvidia-driver-450 proprietary
Nvidia prime profile: NVIDIA (Performance mode)
Screen confirmed to be connected to Nvidia RTX 2060
Nvidia X Server settings shows connection link 4 lanes @ 8.10gbps, 164,06HZ for the monitor.

In journalctl keep getting the following altough don't know if these are related:
nov 02 14:41:07 archy-Lenovo-Legion-7-15IMHg05 /usr/lib/gdm3/gdm-x-session[1702]: (EE) client bug: timer event258 debounce: scheduled expiry is in the past (-1ms), your system is too slow
nov 02 14:41:07 archy-Lenovo-Legion-7-15IMHg05 /usr/lib/gdm3/gdm-x-session[1702]: (EE) client bug: timer event258 debounce short: scheduled expiry is in the past (-14ms), your system is too slow

Reported in the Lenovo forums originally: https://forums.lenovo.com/t5/Ubuntu/Display-issues-Legion-7i-at-1440p-165hz-with-ThinkPad-Dock-Gen-2-on-Ubuntu-20-04/m-p/5046805?page=1#5174098

Fodor Zoltan (archfz) wrote :

The issue happens on 60hz as well.

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