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
2

I encountered the same issue which drove me almost mad because I thought I’m doing something wrong. I’m using a DELL monitor which has an integrated dock, so I connect via a single USB-C cable and all peripherals are connected to the monitor.

I think I found a better work-around that lets me keep PlasmaLogin (using CachyOS).
Simply add this into the systemd service config (systemctl edit plasmalogin.service):

[Service]
ExecStartPre=/usr/bin/sleep 3

This will delay the login screen for 3 seconds and gives enough of time for the DP-Alt-Mode to initialize. I did dozens of reboots and never encountered an issue. It’s an ugly workround, but a working one with no drawback except of 3 seconds additional wait after a reboot.

I’ll try later to see if I can find an initialized state and tap into it to avoid using a static sleep.

However, this issue happens only with the Framework Desktop. With my FW13 Laptop I don’t have any issues. I guess that’s something also Framework should try to address.

Cheers.

3

This is so bad on Framework’s side. I’ve been having multiple issues with the desktop on Linux myself, including this one. BTW, thank you @GhostingBit for that workaround.