Kernel: 4.16.7 My monitor’s native mode is (some variant of) 5120x2880 at 60Hz. When amdgpu is loaded during startup, it picks up this mode from the monitor and switches to it just fine. However, when I start a minimal X (X.Org X server 1.19.5, amdgpu 1.3.0) without /etc/X11/xorg.conf and just an xterm and no window manager, I can see the for a fraction of a second the xterm window in the upper left corner of the screen before the monitor turns black. It’s not turned off, the monitor’s power LED shows that it’s on. When I try to switch to another Linux console with Alt+Tab+F6, nothing happens; the console is not switched (I can verify this because typing “echo -en '\a'” doesn’t beep). After ca. 1:30 min the console finally *is* switched but remains black. The kernel spews out messages about timeouts, and I have to reboot the machine (from ssh or Ctrl+Alt+Del). I can use X with 5K if I restrict the refresh rate to 30 Hz (from “cvt 5120 2880 30”). This bug is present since kernel 4.15.10 or thereabouts, which was the first version where amdgpu would work with dc = 1.
Created attachment 139402 [details] dmesg-4.16.7 5K@60
Created attachment 139403 [details] Xorg.log 5k@60
I would like to mention that “cvt 4096 2304 -r” is a mode that works under X so it may not be the 60 Hz as such but rather the increased bandwidth, which needs DisplayPort 1.3 instead of just 1.2. (However, when X is terminated the Linux console goes black because it seems that the driver cannot switch back to 5k@60Hz.)
Created attachment 139514 [details] dmesg-4.16.7 4K@60
Created attachment 139515 [details] Xorg.log 4k@60
Still present with kernel 4.17.0, xorg amdgpu 18.0.1.
Kernel 4.18.1, xorg amdgpu 18.0.1: All quiet on the Western Front.
I have always wondered why 5k works in the frame buffer but not Xorg. 4.19 bring some progress in this regard and made things more consistent: Now the console stays blank too.
Created attachment 142235 [details] dmesg-4.19.0 with drm.debug=0x1ff
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