amdgpu does not support 3840x2160 at 30Hz on kaveri apu

[Christian König]

Hi Davide,

adding a few of our AMD display people.

In general as already suggested by others opening a bug report to track 
this is the right thing to do.

In the past we had a few bug reports like this because amdgpu is more 
strict in checking hardware limitations.

For example it can be that your HDMI port on the board can only handle a 
certain maximum pixel clock, but radeon is ignoring this while amdgpu isn't.

What you can try to do is to manually override the used mode, e.g. copy 
the modeline used when radeon is active and manually add that using 
xrandr when amdgpu is active and see if it works or not.

Regards,
Christian.

Am 02.01.21 um 19:50 schrieb Davide Corrado:
> hello, I'd like to report this issue that I am having since I updated 
> my display (samsung U28E590). The amdgpu does not support the native 
> resolution of my new monitor, which is 3840x2160/./ Using a HDMI or 
> DVI connection (I tried both, same results), the maximum supported 
> refresh is 30Hz, so I'm stuck with that (don't have a displayport). 
> The radeon module works fine, I'm having this issue just when I use 
> amdgpu (which I'd like to, because performance is better).
>
> Some info of my hardware:
>
> cpu: AMD A10-7870K Radeon R7, 12 Compute Cores 4C+8G
> kernel version (I tried different ones and different linux distros, 
> same results!): 5.9.16-200.fc33.x86_64 #1 SMP Mon Dec 21 14:08:22 UTC 
> 2020 x86_64 x86_64 x86_64 GNU/Linux
> Monitor: Samsung U28E590.
>
> description:
> If I boot the system using amdgpu and no video mode selection, the 
> system boots but I don't get a screen during boot and in wayland. I 
> can connect using ssh, so the system is running fine, just no display; 
> If I force a full HD resolution with "video:" in the kernel line, I 
> can see the boot process but the screen disappears when wayland starts 
> (because the default resolution is 3840x2160 at 30Hz). Using a full HD 
> monitor results in no issues, so it must be related to this very 4k 
> resolution.
>
> As I have already stated, radeon module works with the same 
> software/hardware configuration.
> thanks you so much for your time :-)
>
> -- 
> Davide Corrado
> UNIX Team Leader
>
> Via Abramo Lincoln, 25
> 20129 Milano
>
> Tel +39 3474259950
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

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