Public bug reported:
Ubuntu 26.04 LTS running Wayland on a Dell Precision M6700.
Graphics:
- Intel 3rd Gen Core Graphics using i915
- NVIDIA Quadro K3000M using nouveau
External monitors:
- Dell U3415W 34" connected via DisplayPort (card0-DP-2)
- Dell 2005FPW 20" connected as card0-DP-3
Problem:
After logging out and the displays enter power saving mode, the Dell U3415W
sometimes does not wake up again.
The login screen is not visible on the U3415W, so I have to type my
password blindly.
After login, the second monitor works, but the U3415W remains black.
If I open Settings -> Displays, disable the U3415W and enable it again,
the display immediately starts working.
The monitor is still detected as connected while the screen is black.
The kernel log shows a DisplayPort link training failure at the time of
the problem:
nouveau 0000:01:00.0: disp: outp 05:0006:0f48: training failed
nouveau 0000:01:00.0: drm: [DRM/00000005:kmsOutp] [DP_TRAIN retrain:0 mst:0
lttprs:0 post_lt_adj:0 nr:4 bw:270000] (ret:-1)
This appears to be a nouveau/DRM DisplayPort resume or link-training
problem.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2168660
Title:
Nouveau DisplayPort link training fails after display power save on
Dell U3415W
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