iGPU HDMI not working with recent 7.2 Kernels

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1

I have a machine running fully updated release 44.

After the recent updates to kernel 7.2.5-200.fc44 and then 7.2.6-200.fc44 I do not get graphical output once SDDM takes control of the monitor, however the normal kernel text chatter works fine. If I select the older 7.1.12-200 kernel it works fine.

If I plug the machine into another monitor and boot it the port works, so it’s some sort of issue with the TV it’s normally plugged in to.

CPU is a AMD Ryzen 5 5600G with a Cezanne iGPU. The Motherboard is a Gigabyte B550M AORUS PRO-P with the most recent BIOS installed.

My first question is, how do I prevent it from effectively becoming unbootable next time it’s updated and the 7.1 kernel is removed? Can I stop that package from being removed?

Second question is how do I diagnose the issue further? The machine is used by my father with Parkinson’s and is his bridge to the world, so I am loath to take it away from him for an extended period. I have ssh access to the machine.

The timing of the issue with the 7.2 kernel suggests that it’s related to HDMI 2.1 support.

I have done some searching and found HDMI 2.1 on Linux: AMD, Intel, and NVIDIA Support Guide , and I tried adding the suggested amdgpu.dc_feature_mask=0x400 parameter to the GRUB entry for kernel 7.2.6-200, however it doesn’t fix the issue and the message kernel: amdgpu: unknown parameter 'dc_feature_mask' ignored shows up in the journal.

I hope you can help!

2

I had issues with HDMI cables and using a TV as the monitor.
For me the solution was to replace the older HDMI cables with new HDMI 5.1 cables.

3

But the cable does work in kernel 7.1? Are you saying that even though the TV and cable work together on kernel 7.1 it might not work in kernel 7.2? The resolution works as the default resolution until SDDM/KDE starts.

Is there a way to confirm this before I go and spend money on a cable?

4

Set installonly_limit=5 in /etc/dnf/dnf.conf and UPDATEDEFAULT=no in /etc/sysconfig/kernel, then run sudo grubby --set-default /boot/vmlinuz-7.1.12-200.fc44.x86_64 so the machine keeps booting 7.1 and the next few kernel updates don’t remove it. A cable that works on 7.1 makes a driver change in 7.2 more likely than the cable, but I’d compare the two kernels before buying one. The driver’s option is amdgpu.dcfeaturemask, but the guide’s 0x400 value turns HDMI 2.1 FRL on, so I’d leave it out. Boot 7.2 once, then back on 7.1 run journalctl -k -b -1 | grep -iE 'amdgpu|drm' for the 7.2 boot and journalctl -k -b 0 | grep -iE 'amdgpu|drm' for the current one, and look for amdgpu errors that only the 7.2 boot logged. If there are any, file them against the kernel component in Red Hat Bugzilla with the 5600G and the TV model in the title.

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