Hello. This resolution is supported by the Apu and the motherboard specs.
Will try what you suggest and let you know

Il Lun 4 Gen 2021, 12:10 Christian König <ckoenig.leichtzumerken@gmail.com>
ha scritto:

> 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@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
>
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>
>