Bug 448177

I accidently pressed Enter, submitting the issue, anyways could you give me some ways to debug this problem? I have a lot of time, so please ask questions if you have some or make suggestions how I could fix the problem. 
Thanks very much for your support!

I fucked up with theming in the Video, but I know and I already fixed it so this is not a issue

Operating System: Gentoo Linux 2.8
KDE Plasma Version: 5.23.5
KDE Frameworks Version: 5.89.0
Qt Version: 5.15.2
Kernel Version: 5.15.10-gentoo-x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 8 × 11th Gen Intel® Core™ i7-1165G7 @ 2.80GHz
Memory: 15.3 GiB of RAM
Graphics Processor: Mesa Intel® Xe Graphics

Laptop: Thinkpad E15 G2 (Intel)

The issue is also not specific to Xorg or Wayland.

Means: The problem exsists in Xorg and Wayland

Can you attach the output of drm_info, once for when the display is still working and once when it just stopped working?

Sorry, what do you mean by drm_info? A command? How can I install it or where do I find it?

Yes, it's a command. If your distro doesn't provide it you can compile it from https://github.com/ascent12/drm_info

Created attachment 145413 [details]
drm_info_before_starting_plasma

Created attachment 145414 [details]
drm_info_when_plasma_started

Created attachment 145415 [details]
drm_info_while_bug

Created attachment 145416 [details]
drm_info_after_bug

Ok, I did it. The files are in the attachments

I can't explain why it would be working on xfce Xorg and not Plasma but Sway is using the link-status property (that your hardware has), which is supposed to prevent some black screen situations when the bandwidth requirements of a connector change too much. Sounds like an exact match.

A possibly relevant merge request was started @ https://invent.kde.org/plasma/kwin/-/merge_requests/1878

Git commit 802d855785d9cecca8c674a0aa61bba44293cbbb by Xaver Hugl.
Committed on 14/01/2022 at 10:31.
Pushed by zamundaaa into branch 'master'.

backends/drm: support link-status

Userspace is expected to do a modeset and set link-status to good again,
if link-status gets bad. This is needed to prevent some black screen situations.

M  +12   -0    src/backends/drm/drm_object_connector.cpp
M  +6    -0    src/backends/drm/drm_object_connector.h
M  +4    -0    src/backends/drm/drm_pipeline.cpp

https://invent.kde.org/plasma/kwin/commit/802d855785d9cecca8c674a0aa61bba44293cbbb

Git commit 04b51655a16b46be1f77d1539aa450b36e018ed1 by Xaver Hugl.
Committed on 14/01/2022 at 12:06.
Pushed by zamundaaa into branch 'Plasma/5.24'.

backends/drm: support link-status

Userspace is expected to do a modeset and set link-status to good again,
if link-status gets bad. This is needed to prevent some black screen situations.


(cherry picked from commit 802d855785d9cecca8c674a0aa61bba44293cbbb)

M  +12   -0    src/backends/drm/drm_object_connector.cpp
M  +6    -0    src/backends/drm/drm_object_connector.h
M  +4    -0    src/backends/drm/drm_pipeline.cpp

https://invent.kde.org/plasma/kwin/commit/04b51655a16b46be1f77d1539aa450b36e018ed1

I'm relatively sure that this will fix it but if the issue should still happen with that commit (or 5.24.0) do please re-open the bug report

Thank you very much!!!
I hope this works, when kde 5.24 was released. 
Sadly, I cannot test if that works, because I cannot apply the patch to kwin-5.23.5 (There was a lot going on, for example moving all the stuff to the backend dir, but also the file was changed a lot).

How can I test if this works? Gentoo doesn't provide a nightly kwin package, can I download the source from gitlab and compile it? 
Or does kwin 5.24 contain breaking changes with the current plasma version?

You can try but it definitely has some breakages on the build side. You'll at least need KWaylandServer, KDecoration and plasma-wayland-protocols to be up to date, too. If you want to do it you should probably use kdesrc-build, it builds all the dependencies and sets up a dev session for testing: https://community.kde.org/Get_Involved/development#Set_up_kdesrc-build

The easiest way to test though is to wait until KDE Neon unstable rebuilds (one or two days) and then use that as a live boot.

--- REOPENING ---
So I downloaded the kde neon version yesterday, the filename was "neon-unstable-20220116-0330.iso", so I assume this is the newest build.
The issue is still around: https://www.youtube.com/watch?v=JeI0T_m4-94

It's not surprising that it doesn't work on X, nothing changed regarding that (and nothing can change from our side). How do things look on Wayland?

They look the same: https://www.youtube.com/watch?v=VJ-43-2R-EQ

(I mean that 30Hz looks as laggy as 60Hz doas.)

If you don't have any ideas, please, could you give me some recommendations on how to debug this?

For the lag you may have been affected by a recently fixed regression in git master. In terms of what to do about the black screen, I have no further ideas on how one could debug it - but you could maybe get more help at https://gitlab.freedesktop.org/drm/intel/-/issues

Let's close it until we know for sure that it's kwin's fault and not some hardware or driver issue. Regarding the black screen, I've experienced somewhat similar issue (+ other weird visual artifacts) when I tried to connect a 4k monitor to a video card that couldn't drive it 100% or attaching a fhd monitor with high refresh rate (atomic commits succeeded in both cases even though they shouldn't have).

I would like to chime in here because this seems locked. 

I am also like OP except I use a Lenovo USB-C 7-in-1 Hub for my 4k monitor & thinkpad which is kubuntu 21.10 

Plasma: 5.22.5
QT: 5.15.2
Kernel: 5.13
Graphics: X11

There is a flicker when there is screen movement. at 4k 60hz but not when it's at 30hz. 

I think this is worth a look because I am considering making a switch from KDE because 30hz has been a pain.