Thunderbolt displays gnome/kde linux?

Operating Systems & Open Source Linux
1

Good morning from where I am.

I wanted to get some ideas or comments on my particular situation.

Ever since I used a 5k monitor I’ve gotten use to it. Fast forward to this year.

Wanting to get back to using it with my Linux gear I thought I would try it out with a laptop I had loaded with Fedora 40. I really had zero hopes that it would work. This was a X1 extreme gen1 that came with a thunderbolt 3 port.

Surprisingly everything worked, camera, sound and all devices that were plugged into the monitor like mouse/keyboard. I was ecstatic. Wanting to proceed to the next part I put together a new AM5 system.

The core components were

  • asrock b650m pro rs
  • asrock thunderbolt 4 aic rev 2.0
  • cpu 7950x
  • gpu 7900 gre

The plan was I would plug from the 7900gre → DP1 OUT → DP1 IN (AIC) → thunderbolt out

Basically I just wanted to mimic what I with the laptop.

However heres the sad part

  • live usb (fedora 41) grub comes up only when it hits gnome even before it gets t there I can see like static artifacts on the screen, then the screen blanks out.
  • live usb (cachyos kde) this time it does make it in but there is so much static here and there that it is unusable.
  • live usb (nobara) same as cachyos, so i’m thinking they are both kde this might be the reason.

Perhaps it’s my setup? Thats what I thought. Now it’s been practically forever since I installed Windows but I did. And you know what it worked!!!

Sound/Camera/attached devices all worked with my new hardware through thunderbolt.

So is something weird going on with Linux that I haven’t configure or I don’t know how to diagnose.

The only conclusion I can come to is that the x1 is using 1050ti and i’ve configured it for nvidia drivers. So their proprietary driver is making it work??

AMD driver is lacking? or is it wayland?? Kde is fairing better, i haven’t looked i’m guessing it’s X11?

The final symptom I’ll present is that in both the KDE installations for nobara/cachyos will install if I persist with the “static” all over the installer. The sound/keyboard/camera is actually working. AND once installed if I change the resolution to 4k the “static” disappears. So thats one workaround.

So the question is can I do something to make it work through thunderbolt at 5k that I’m overlooking or is there something missing in AMD driver in linux. Suggestions and comments would be very well received.

2

Have you tried the thunderbolt out via the iGPU? Does that work? I am using the TB4/USB4 output on my mainboard from the iGPU and it’s working fine. It’s not a TB display though, I’m just using it’s DP signal, don’t know if that matters.

Maybe try a live fedora 40? I have been having amdgpu issues with fedora 41. quite annoying. But not with output per se rather the DE crashing due to gpu ring timeout.

3

I did that too.

I tried ubuntu LTS liveusb
I also tried Fedora 40 liveusb

both boot to blank screens. I know it made it because there sounds coming from the monitor.

I haven’t tried the inbuilt igpu through usb c (?) but

in Nobara when I am at 5k with all the static going on … if I then take the cable out from the thunderbolt DP In and instead connect the displayport to usb c to the monitor I still get 5k and the static weird disappears.

Down side of that is the keyboard/sound/camera is not passed back through it …

Holding out hope theres more suggestions.

I did install using the igpu’s HDMI but i’ve not been able to get usb c through the igpu … there must be something in the bios I don’t know about.

4

Its a crapshot:
Have you checked if the thunderbolt controller device authentication is disabled (or similar sounding setting)? TB device authentication by default is set to “on” on most UEFIs and connected TB devices need to be approved by the user in the OS (which is not possible if this is your only display). I would disable thunderbolt authentication, so all TB connected PCIE-based devices work during OS boot. This would also explain why you might get adistorted display or no display out on boot. (The thunderbolt controller might still be acting as USB-Hub in this case and may enable some USB devices to function)

5

If I could see this authentication thing in the bios I would although I did read somewhere that thunderbolt 3 and above it’s automatically authenticated, I lost the link already but does seem to be true.

With the KDE distros where I get this weird static the 5k display is authenticated and trusted. This I can see in the settings.

But I do feel its like a resolution/thunderbolt driver issue. Because if I bump the rez down to 4k the KDE distributions work fine. The static disappears BUT it is on the login screen until I get in. Presumably the login screen picks the best which would be 5k.

The only distros with nothing coming out are gnome based distros.

Bear in mind that in Windows all this works perfectly.

At the moment I’m trying to figure out if I can somehow make a gnome based distro use the closed source driver. From the reading there should be no difference …

6

Can you post the model of the 5K screen, maybe I can find something out. I had something similar happen with 1440p screen but only during boot with an Intel iGPU, it displayed an unsupported mode which resulted in a garbled screen - mostly green with a very squished and repeated picture I could barely make out.