amdgpu bringup on A12-8800B FreeBSD

[Johannes Dieterich]

Dear list,

as Matthew Macy informed a few weeks ago, he is in the process to port
linux 4.6 DRM/KMS drivers to FreeBSD using the linuxkpi wrapper.

We are now at the point that the amdgpu attaches and does useful stuff
thanks to him. However, the AMD hardware we use for testing behaves
rather erratically and we are a bit at loss to understand this
behavior.

Namely, we have a few APUs that don't even pass ring attachment (this
is for another day). Fortunately, my A12-8800B does not suffer from
this, it has serious issues with displays though. The internal display
simple does not display anything (the driver seems to disconnect the
internal display), one tested external displayport monitor works
correctly, another does not at all. Since the code is not too
verbosely documented, we are a bit at a loss where to look for
problems and would appreciate pointers a lot!

Please see a verbose log of amdgpu/drm at http://pastebin.com/nmh6xzqq
showing amdgpu attaching with the internal display (1920x1080) and a
working external display (2560x1440) connected via displayport. This
is simple console, no X involved. After amdgpu attaches, I get a
working console on the external display and nothing on the internal.

Ideally, I am looking for information what fails for the internal
display and where to look to fix it based on the log.

I am happy to provide any other information necessary.

Thanks for any help, we truly appreciate it!

Johannes