Wayland and Blank Screen after Login Screen Fedora38 with Amd Gpu A10-9700

I was using Kernel 6.2.15 and everythings was fine.

But when I upgraded to 6.5.5 … I got blank screen after Login - Wayland.

I started to search for the root cause and I only found that I must enable in Bios IOMMU for graphics in Processor settings.

Then I updated Grub → /etc/default/grub with new parameter amd_iommu=on.

GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR=“$(sed ‘s, release .*$,g’ /etc/system-release)”
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT=“console”
GRUB_CMDLINE_LINUX=“rhgb amd_iommu=on”
GRUB_DISABLE_RECOVERY=“true”
GRUB_ENABLE_BLSCFG=true

So I started new kernel 6.5.5 and nothing changed.

I started to think why is so:

  1. kernel 6.2.15 with resolution 1920x1080 is ok
  2. kernel 6.5.5 with default resolution is not ok.

So I changed resolution to FHD->4K … in kernel 6.2.15 and then restarted 6.5.5 in 4K. WORKS!

So then I changed 6.5.5 to FHD and … screen blank. Then I booted in 6.2.15 and changed it to 4K.
Works. The only next change I change scale to 200%.

My native resolution for Monitor (Lenovo T27p-10) is 4K … I assume Linux is delivering default resolution for end device. Bad info is: in my case refresh rate it is only 30Hz at 4K (expected usually 60Hz).

Maybe it is helpfull for somebody but it looks like:
Default resolution with default refresh rate is the main problem for “Blank Screen Problem”.

BR
T.

Some GPUs are only able to do 4k at 30 Hz. Some can do 60 Hz. Sometimes the cable also may limit the refresh rate. The monitor also may limit the refresh rate at 4k.

Check all your hardware and specs to verify that both the GPU and the monitor are able to handle 4k @ 60 Hz, then also maybe verify the cable quality is adequate for 4k 60 Hz.

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In my case it is exactly as you wrote.

My processor APU (AMD A10-9700 has build in GPU Cores) and can handle ONLY 30Hz in 4K and FHD max 60Hz.
(I use original HDMI Cable from Lenovo)

So generally the problem is not with Wayland or with Linux Config but with … hardware limitations and what is written in config.

I am not sure but is there any option to change screen resolution in Wayland via Shortcuts or special keys_?I remember in X was some option with “Ctrl and +” to have step higher resolution 600x400, then 640x480 etc.
Or is there any way to probe which resolutions GPU/Monitor Supports?

You can decode the monitor EDID to see what is possible.
But that should be shown in the DE display setting.

find /sys -name edid
# for each edid file do
edid-decode < edid-file-path

As far as I know there is no way to override the hardware limitations. On a 4k monitor you might be able to use 200% scaling with 1920x1080 @ 60 Hz resolution to make it seem like a 4k display, but I doubt that would be preferable to using actual 4k @ 30 Hz.

200% doubles the size of the pixels. so at 1920x1080 its as if you have a 960x540
Using 50% will give very poor results, especially for text.