DisplayPort 4K monitor no longer works after kernel upgrade

Ask Fedora
1

Hi,

I use Librem Mini v2 (specs: Purism – Librem Mini ) which only supports 4K monitors with DP (HDMI only works for 1080p and maybe QHD but I never had such monitor to know this).

I am stuck on Fedora 43 because kernel 6.18.16-200.fc43.x86_64 is the last one that inits the monitor correctly past GRUB. On newer kernels, after GRUB, the monitor goes to sleep and only wakes up after reconnect.

On a fresh Fedora 44 test install on external drive, also after GRUB I have to physically reconnect DP cable and then it works, but I have to do it every time so I didn’t upgrade yet on my main install.

Checking logs on my current install is more difficult because I have LUKS encryption and can’t really see boot logs at this point and they don’t persist before decryption. However, on the decryption screen it shows this:

boot
boot3380×388 538 KB

After booting on my current Fedora 43 I only found this in kernel logs:

i915 0000:00:02.0: [drm] *ERROR* Failed to probe lspcon
i915 0000:00:02.0: [drm] Registered 3 planes with drm panic
[drm] Initialized i915 1.6.0 for 0000:00:02.0 on minor 0
fbcon: i915drmfb (fb0) is primary device
fbcon: Deferring console take-over
i915 0000:00:02.0: [drm] fb0: i915drmfb frame buffer device

Upgrading to newest coreboot with their script: https://source.puri.sm/firmware/utility didn’t solve this either.

Unfortunately I don’t have any other monitor to test if it works fine with 1080p or another 4K DP monitor.

I’d appreciate any help.

2

I use external 4k monitor with the USB4/TB3 cable from aliexpress, and with fedora 44 the connection stability has actually improved: with F43 monitors could blink time to time, with F44 (or rather, new kernel) this barely happens. I also use it with Intel Xe driver, not i915.

From your logs it appears that you are on Intel integrated graphics, and that Intel i915 video driver is not happy with something.

I’d suggest first of all trying to switch from i915 driver to intel Xe (if your platform is supported - which is very likely)

then purchasing a reliable usb4 or better thunderbolt 3/4/5 cable which could help too.

3

Hi, thanks for the reply, but switching to XE with this guide: How to use intel XE graphics driver on Fedora Linux - #4 by jflory7

resulted in dead monitor, not working even after reconnecting.

I tried a random USB-C cable but it didn’t detect a USB-C connection. Will try with a better one later.

4

Random will not work, you need a quality one that supports USB-C 4.

Thunderbolt 4/5 are the best, they are also suitable for fastest data transfer.

5

When you do the upgrade to f44 the working kernel will be left installed and usable.

You can use f44 with the 6.18 kernel.

If you want to make sure that the intel developers fix there driver you will need to report the bug to them. This seems to be where you should report bugs Making sure you're not a bot!