re: kern/56729: amdgpu X driver nearly (but not quite) working

[matthew green <mrg%eterna.com.au@localhost>]

>  right now i have a 5450 installed, but i'll put the RX550
>  back in and see what the latest status is.

with the RX550 i am now able to run 12x glxgears for about an hour
before the X server crashes, and mpv is capable of going into and
out of fullscreen mode without corrupting anything else.

the crash is inside glamor module, possibly some map/unmap race
as the faulting address always seems to be accessible in GDB.

while not great, this is far more usable than any prior so far.

unfortunately, i get crashes on a ryzen pro 3700U CPU's amdgpu.
some command times out, and it either crashes with a LOCKDEBUG
error (i have a patch for this part), or then with cnopen panic
no console as no framebuffer/console is attached now.

i'll file a separate PR about the 3700U issue, as it is
unrelated to it sort-of working.


.mrg.