I’m having weird issues with my new display setup (USB-C → Dell U2724DE → Dell U2724D) and the FW 13 AMD on Fedora 40: All works well when connected to the front right port (The screen acknowledges the USB3 connection), but when I connect to one of the USB4 ports, I get unpredictable results for the displays. In all cases, the USB devices are working fine and I think in all cases the displays appear working in gnome settings.
Most times, the displays stay black and I get a “no thunderbolt signal detected” message. This usually comes with dmesg showing
amdgpu 0000:c1:00.0: [drm] *ERROR* Sending link address failed with -5
Sometimes the second display (U2724D, daisy chained through DP) switches on while the first display in the chain doesn’t show anything. The error message that I’ve seen repeatedly with this issue is
amdgpu 0000:c1:00.0: [drm] *ERROR* Step 2 of creating MST payload for 0000000078e80139 failed: -5
Sometimes - rarely - both displays work after waiting for a minute or two.
Can anyone make sense of this behaviour and point me to a solution?