Created attachment 296833 [details]
relev_out

The following issue started with the 5.10.33 vanilla kernel (currently I am on 5.10.37 vanilla). I get my kernels (incl. firmware, modules and headers) through my distro.

My graphics card is a Radean RX 560, on which I use all three heads: DisplayPort 1.2, HDMI and DVI.


Here is the issue:
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At the beginning of the kernel boot process, the frame buffer fonts on all three heads are normal size. But as soon as amdgpu takes over during the boot process, the font on the DisplayPort changes to this:
1) the fontsize goes tiny;
2) only the upper-left quadrant of DisplayPort is used.

Fonts on the other two heads are unaffected.

When I disconnect the cables from HDMI and DVI, so that I only use DisplayPort, then fonts remain of a good size and the full screen area is used.

I attach the relevant output of lspci and dmesg, with all heads connected.