Using drm-next in 11.2

[CL Moonriver]

> also, please ensure you are booting in "classic" BIOS mode and not
> UEFI, IIRC there are some issues surrounding amdgpu with UEFI - i
> don't have that hardware tho so can't elaborate.

Just to add to this, the conflicts involve kernel mode switching
between the scfb driver and the AMD driver. However, there are work
arounds for it. And in all honesty, with AMD A10 series CPU, I've
actually found it easier to get things working properly in UEFI mode
instead of classic / legacy / bios mode.

The work around (as I learned from a thread in the x11 mailing
lists) involves disabling the system console completely by adding
hw.syscons.disable=1 to /boot/loader.conf. Obviously, this is not
without some risk. But it does work for me. And I have had no problems
at all with radeonkms.ko since doing this. (The only problem I had
before adding this was the occasional X server hang where the GPU had
to be restarted. But even that problem is gone now.)