USB-C DP-Alt-Mode blank screen

Framework Desktop
1

Hi,

Got my Framework Desktop last month and super happy with the form factor (apart from the noisy PSU fan which was solved by upping the CPU fan speed).

I run everything through a Thunderbolt 4 cable with DP alt mode through a Sabrent KVM (connected to a Mac Studio on the other port). I initially installed Linux Mint and it worked for a while but then the screen kept going blank and would only sometimes work by rebooting.
I switched to Endeavour OS and found the same issue.

After many hours troubleshooting with my friend, who we’ll call ‘Chad Gippetti’, I finally cracked it that the Display Core is loading in too early which seems to conflict with DP alt mode. I have logged a bug here: https://gitlab.freedesktop.org/drm/amd/-/issues/4940.

If you have this problem, there are a few options but they vary in ugliness.

  1. You can install an alternative TTY display manager and configure it to load X/Wayland after login - this was my approach, I’m using tuigreet - GitHub - apognu/tuigreet: Graphical console greeter for greetd .

  2. You can disable the AMD Display Core entirely: amdgpu.dc=0 I am reliably informed this doesn’t disable the GPU and you can certainly use it for AI and gaming - but there are a few advanced features that would be turned off, such as HDR.

  3. You can continue with the default modern DM and use a DisplayPort cable, until you’ve got past login and then physically switch to USBC DP alt mode (e.g. if you are plugged into a monitor, use the input switch). This just wasn’t acceptable for me as I’ve put a lot of money into my cable minimisation.

I hope this helps if you’re struggling with the same thing, and I hope the bug gets fixed. I accept however that I’m pretty much and edge case!

4 Likes