Testing/Debugging amdgpu kernel driver in 10.0_BETA

[Jeff Frasca <thatguy%jeff-frasca.name@localhost>]

Hi all,  I have a lenovo thinkpad E485 which has a Ryzen 3 2200U APU
in it (which is a Vega/RAVEN RIDGE GPU).  I installed the NetBSD 10.0
BETA on it this week, and that's actually working better than
Slackware 15.0 (which just refuses to boot).  Everything seems to be
working reasonably well, and X11 runs with the framebuffer drivers and
llvmpipe.  However, that only gets me 1024x768, and I know there's a
big chunk of code sitting in the src tree that has the real drivers
for it.

I've got three kernels installed right now.  The GENERIC kernel from
the install, a custom kernel that just has the drivers I need and is
setup to run with the framebuffer drivers.  Both of those seem to work
equally well.  The third is another custom config that is the same as
the working custom kernel, it just has the amdgpu drivers configured.

That third kernel panics on boot in one of two ways:

On cold boot, I get an error "PSP load tmr failed!"

On a warm boot (after first loading any of the three kernels), I get
an ETIMEDOUT error from the ring_test function in the driver.

In both cases, that isn't the actual panic, it's a failed
'cv_is_valid()' assertion in a call to 'cv_destroy()' in
'drm_sched_fini()'.  I think both of those errors are causing the
'amdgpu_driver_load_kms()' to fail, emit a "Fatal error during GPU
init" and then jump to an error block which calls
'amdgpu_driver_unload_kms()' which then panics while trying to unload
the driver.

Anyone have any tips on how to further debug this?  I'm going to keep
poking at it on my own, but any suggestions on where to look, things
to try, I would love to hear them.  Is there any more information I
can/should send?  Is there a good way to save backtraces and dmesg
rather than typing it into an email manually on a different computer?
Any cute ddb tricks that would help?  I know this is going to need
code changes (which I will try to work out), is there a better mailing
list to send this to?

(I'm typing this from a Kaveri APU based desktop that's dual booting
Slackware 15 and NetBSD 9.99.x right now, if I make headway on the
laptop, the desktop will get 10.0 next and I'll try and get bugs in
its graphics drivers tested and ironed out.)

Thanks!
Jeff