SUMMARY Upon connecting a 4th monitor to the system, logging in through SDDM on a Wayland session results in a black screen/stall, spamming journal with error messages, this is irrecoverable and the only workaround is to disconnect 1 monitor. A snippet of the logspam is as follows: Jul 20 17:27:16 localhost.localdomain kwin_wayland[2227]: kwin_scene_opengl: 0x502: GL_INVALID_OPERATION error generated. <image> and <target> are incompatible Jul 20 17:27:16 localhost.localdomain kwin_wayland[2227]: kwin_scene_opengl: Invalid framebuffer status: "GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT" Jul 20 17:27:16 localhost.localdomain kwin_wayland[2227]: kwin_wayland_drm: Checking test buffer failed! Jul 20 17:27:16 localhost.localdomain kwin_wayland[2227]: kwin_wayland_drm: Atomic modeset test failed! Invalid argument STEPS TO REPRODUCE 1. Obtain a GPU with at least 4 ports 2. Connect 4 monitors to the GPU 3. Boot the system into SDDM 4. Login OBSERVED RESULT System will hang on a black screen, rendering it unusable until a hard restart (either through REISUB or power-cycling) EXPECTED RESULT The system boots into the desktop with output on at least one monitor. SOFTWARE/OS VERSIONS Operating System: openSUSE Tumbleweed 20250714 KDE Plasma Version: 6.4.2 KDE Frameworks Version: 6.16.0 Qt Version: 6.9.1 Kernel Version: 6.15.6-1-default (64-bit) Graphics Platform: Wayland Processors: 32 × AMD Ryzen 9 7950X3D 16-Core Processor Memory: 64 GiB of RAM (62.4 GiB usable) Graphics Processor: NVIDIA GeForce RTX 4090 ADDITIONAL INFORMATION This has been happening to me since at least Plasma 6.3 (I didn't test any earlier versions). No-repro on X11 No-repro on alternative DEs HDR/VRR status appears to not affect this issue Deleting kwinoutputconfig.json SOMETIMES appears to resolve this issue, but the easier solution is to physically disconnect a monitor. The displays in question: 1 x Dell U2715H, connected via DP 1 x Alienware U3225QF, connected via DP 1 x Dell S2721DGF, connected via DP -> HDMI adapter 1 x Onkyo NR7100 AV Reciever, connected via known-good compliant HDMI 2.1 fiber-optic cable. It doesn't matter which monitor is disconnected to resolve the issue, it appears no-repro on 3 monitor setups.
Just a note to say that this looks very similar to https://bugs.kde.org/show_bug.cgi?id=500819 but I am on a much higher version of Plasma, so I’m not sure if it’s related. This is 100% repro for me, issue does not happen if I unplug a fourth monitor.
There's a good chance this is just caused by the driver not handling bandwidth limits properly. In Plasma 6.4, you can limit the color resolution to a lower value, please test if setting that on all screens helps.
I don’t see an option to set this anywhere - should it be in display options?
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Unfortunately I do not see the color resolution option in the display settings panel. Adding this info in case this is another bug in itself.
Created attachment 184505 [details] This is what you should see
This option is not there for me, on a discussion thread I opened it was mentioned that it might not be supported on my RTX4090, this is the link that was given: https://drmdb.emersion.fr/properties/3233857728/max%20bpc
It sounds like there may be multiple hardware or driver bugs here, unfortunately. I'll let the KWin folks decide if there's anything we can do about it in KWin.
(In reply to Nate Graham from comment #8) > It sounds like there may be multiple hardware or driver bugs here, > unfortunately. I'll let the KWin folks decide if there's anything we can do > about it in KWin. Thank you! Please don’t hesitate if there’s anything more I can provide to help.
Yeah, I think this needs to be reported at https://forums.developer.nvidia.com/c/gpu-graphics/linux - at a minimum, NVidia needs to add the "max bpc" property, so that we can limit bit depth, but drivers are supposed to do that automatically as well
Sorry for the additional bump - Is there anywhere else I can report this? I'm reporting as a home user, and therefore can't sign up for an NVIDIA Developer account.
I also see that 580.76.05 came with the following patch notes: "Added an "OutputBitsPerComponent" MetaMode attribute that can be used to control the number of bits per color component transmitted via a display connector. If not specified, the driver will choose an optimal color format." https://www.nvidia.com/en-us/drivers/details/252613/ Is this related?
Appears to be resolved as of 580.105.08.
(With the caveat that enabling all 4 monitors results in a black screen but can eventually be cancelled with the output: "Couldn’t apply display configuration: The driver rejected the output configuration" It is not longer a fatal stall that requires a forced reboot of the machine.