SUMMARY After upgrading from Fedora 41 to 42, my dual display setup no longer works correctly. Only one display can be activated at a time. Main display is on display port, secondary is on HDMI. STEPS TO REPRODUCE 1. Use an AMD GPU (Radeon RX580) 2. Plug an UHD (4k) display to its Display Port output 3. Plug another display (1080p) to its HDMI output 4. Open Plasma settings > Display & Monitor 5. Enable both displays at max resolution 6. Apply OBSERVED RESULT Secondary display is not enabled An error appears; "Couldn’t apply display configuration: The driver rejected the output configuration" EXPECTED RESULT Secondary display is enabled. No error occurs. SOFTWARE/OS VERSIONS Operating System: Fedora Linux 42 KDE Plasma Version: 6.4.1 KDE Frameworks Version: 6.15.0 Qt Version: 6.9.1 Kernel Version: 6.15.4-200.fc42.x86_64 (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen 5 1600X Six-Core Processor Memory: 16 GiB of RAM (15,5 GiB usable) Graphics Processor: AMD Radeon RX 580 Series OpenGL vendor string: AMD OpenGL renderer string: AMD Radeon RX 580 Series (radeonsi, polaris10, ACO, DRM 3.63, 6.15.4-200.fc42.x86_64) OpenGL core profile version string: 4.6 (Core Profile) Mesa 25.0.7 ADDITIONAL INFORMATION I can still enable my HDMI output if I disable the Display port output before applying. I can enable both displays if I set them both to 1080p resolution. When the error occurs, I see the following log in journalctl: kwin_wayland[2064]: kwin_wayland_drm: Atomic modeset test failed! Invalid argument
With the two displays connected, please attach the output of > drm_info > kscreen-doctor -o and follow https://invent.kde.org/plasma/kwin/-/wikis/Debugging/Debugging-DRM-issues to get a drm debug log of you trying to enable the second display.
Created attachment 182909 [details] drm_info output
Created attachment 182910 [details] kscreen-doctor output
Created attachment 182911 [details] drm logs Logs taken while reproducing the issue by enabling my hdmi display. Compressed otherwise it exceeded the file size limit.
Alright, this is the culprit: > [ 369.622233] amdgpu 0000:08:00.0: [drm:dce112_validate_bandwidth [amdgpu]] dce112_validate_bandwidth: Bandwidth validation failed! > [ 369.622276] amdgpu 0000:08:00.0: [drm:dm_pflip_high_irq [amdgpu]] crtc:0[000000004a242ee5], pflip_stat:AMDGPU_FLIP_NONE, vrr[0]-fp 0 > [ 369.622660] amdgpu 0000:08:00.0: [drm:amdgpu_dm_atomic_check [amdgpu]] DC global validation failure: Bandwidth validation failure (BW and Watermark) (13) > [ 369.623082] amdgpu 0000:08:00.0: [drm:amdgpu_dm_atomic_check [amdgpu]] Atomic check failed with err: -22 > [ 369.623514] amdgpu 0000:08:00.0: [drm:drm_atomic_check_only] atomic driver check for 00000000d4205289 failed: -22 I'm pretty sure the rx 580 is able to drive 4k + 1080p without any issues. You can report this driver regression at https://gitlab.freedesktop.org/drm/amd/-/issues - and attach the drm_info output and drm debug log there as well.
(In reply to Zamundaaa from comment #5) > Alright, this is the culprit: > > [ 369.622233] amdgpu 0000:08:00.0: [drm:dce112_validate_bandwidth [amdgpu]] dce112_validate_bandwidth: Bandwidth validation failed! > > [ 369.622276] amdgpu 0000:08:00.0: [drm:dm_pflip_high_irq [amdgpu]] crtc:0[000000004a242ee5], pflip_stat:AMDGPU_FLIP_NONE, vrr[0]-fp 0 > > [ 369.622660] amdgpu 0000:08:00.0: [drm:amdgpu_dm_atomic_check [amdgpu]] DC global validation failure: Bandwidth validation failure (BW and Watermark) (13) > > [ 369.623082] amdgpu 0000:08:00.0: [drm:amdgpu_dm_atomic_check [amdgpu]] Atomic check failed with err: -22 > > [ 369.623514] amdgpu 0000:08:00.0: [drm:drm_atomic_check_only] atomic driver check for 00000000d4205289 failed: -22 > > I'm pretty sure the rx 580 is able to drive 4k + 1080p without any issues. > You can report this driver regression at > https://gitlab.freedesktop.org/drm/amd/-/issues - and attach the drm_info > output and drm debug log there as well. OK, thanks a lot for having a look!