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

[Deucher, Alexander]

[AMD Official Use Only - Internal Distribution Only]

You might try enabling DC (the newer modesetting infrastructure).  Append amdgpu.dc=1 to the kernel command line in grub.

Alex

________________________________
From: Davide Corrado <davide at davidecorrado.eu>
Sent: Saturday, January 2, 2021 1:50 PM
To: Deucher, Alexander <Alexander.Deucher at amd.com>
Cc: Koenig, Christian <Christian.Koenig at amd.com>; airlied at linux.ie <airlied at linux.ie>; daniel at ffwll.ch <daniel at ffwll.ch>; amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>; dri-devel at lists.freedesktop.org <dri-devel at lists.freedesktop.org>; linux-kernel at vger.kernel.org <linux-kernel at vger.kernel.org>
Subject: amdgpu does not support 3840x2160 at 30Hz on kaveri apu

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
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