Hi,
I have a ThinkPad T14 Gen4 (AMD Ryzen 5 Pro 7540U) with a ThinkPad Universal USB-C dock. Attached to the dock are two 4K 60Hz monitors via DP and Gnome (X11 and Wayland) or Sway as WM.
I used nixos-unstable with flakes. After a flake update and the following rebuild, I can no longer use my external monitors with 4k 60Hz resolution. Lowering the resolution to 1080p or reducing the refresh rate to 30Hz solves the problem. If I roll back to a previous configuration/build, everything is fine.
I tried things I found online, like DisplayLink or not working docks, changing the USB port, but none seems to be the solution. boltctl isn’t showing anything, but I would guess my dock is working, as the monitors are detected and my Ethernet connection is working.
Finally, I tried to “downgrade” my system to nixos-24.04, but the issue still exists. I tried to diff my configuration, but out of noobieness, I don’t have the system.copySystemConfiguration set to true, nor I committed my changes in git. Manually checking the config and figuring out what could be the problem wasn’t helpful.
I’m really new to the whole NixOS world, and I would be happy if we could figure out, what the problem is. Thanks!
I don’t have a solution but I can confirm the same problem. I’m on a T14 Gen 4 with a USB-C dock. I have one external monitor which is 5120 x 1440 via DP and it just broke when I updated this evening. Plug the monitor in via the dock and it is detected but nothing displays. I am using 24.05 with flakes. I had to get some work done and reverting to the previous build fixed everything so I haven’t had time to investigate further at this point.
Hi,
yes, lowering the resolution or lowering the refresh rate solves the problem. Bandwidth sounds reasonable. If I try to set a resolution above this bandwidth, it even says that my hardware does not support it. Even though it was possible in the past. I also tried to disconnect other devices from the dock to reduce the traffic a check if this changes something, but without any success.
