Graphical issue along top of screen in KDE with AMD GPU

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1

Hello,

I’m using Fedora 43 KDE. Sometime last month (possibly at the same time as I updated amdgpu or Mesa or something?), I started occasionally getting a graphical issue at the top of my screen. It wasn’t a big deal—it always went away if I restarted, and I figured if a bad update caused it, it would probably be fixed shortly. Today, I’ve restarted several times and the graphical issue remains. I have no integrated graphics, only a dedicated AMD GPU. (At the time of posting, I did get the issue to go away as described below, but if the issue is happening more frequently now I would like to find a solution if possible.)

I will do my best to describe the issue, and I also have a photo (as I don’t think the issue shows up in screenshots).

PXL_20260407_190504009
PXL_20260407_1905040091920×1446 505 KB

The issue only happens on some log ins, but here is a description for the times that it does happen:

  • The graphical issue features diagonal lines, though closer to horizontal than vertical, going across the top of my screen. It is always the top of my screen, and the lines are always sloped such that they are lower at the left than at the right.
  • The issue only happens when I am logged into Fedora KDE—it doesn’t happen on the BIOS, or even at the SDDM (I think?) log-in prompt.
  • I’ve just tried switching to an X11 session (I typically use Wayland), and the issue went away. I then switched back to Wayland, and the issue is still gone. So I don’t know if the issue can happen in X11, or if the inconsistent nature of the bug is what caused it to go away when logging out and back in.
  • The lines are always there when in my plasma session and always flickering very quickly. (I could upload a video, but that seems like overkill.)
  • I say “always”, but I’ve found one exception so far—the lines go away if I open Spectacle (whether through the PrtSc button or otherwise), but the lines are only gone while I am NOT moving my cursor. If I have Spectacle up and am waggling the mouse, the lines flicker as usual, but they’re gone completely when I keep the cursor still.

Any ideas? I assume it’s a software issue (rather than GPU or monitor) since it seems dependent on what software is running.

2

Do you have another monitor to test against?
Do you have a different cable to test with?
Can you test usinf a differebt port on the gpu?
If using hdmi can you test with dp?

3

Sorry for waiting such a long time before replying, but the issue only happens inconsistently, so it took quite a while to be confident of what was/wasn’t working testing with different monitors, cables, ports, and HDMI vs DP.

After testing, it seems the issue is related to Adaptive Sync. It seems that if I have adaptive sync on, the issue occasionally happens, and if I have adaptive sync off, the issue never happens. Given Adaptive Sync is a DisplayPort thing, it never happens on HDMI. It happens regardless of the GPU port I use. I believe I only have one monitor and one GPU that support Adaptive Sync (or at least AMD’s implementation of it?), so it’s hard for me to say if the problem is my monitor, my GPU, or somehow Fedora. (I don’t know enough about the technology to know what is most likely.)

Some of my games basically require Adaptive Sync or the choppiness is intolerable. I guess for now I’ll plan to turn on Adaptive Sync only when needed, unless someone knows more than I do about Adaptive Sync and has a fix. This is possibly related to Screen Artifacts with Adaptive Sync on Wayland (Fedora 39 KDE), though my artifacting looks slightly different.

Thank you!

4

Glad you found a solution. Would you mark your reply as the solution please?

FYI: HDMI 2.1 supports adaptive sync, but the linux drivers are the moment do not support HDMI 2.1. That support is coming from AMD and will land in a few months, if the reports on Phronix are correct.