[RFC] drm/radeon: restoring ring commands in case of a lockup

[Christian König]

Hi,

The following patchset tries to save and restore the not yet processed commands
from the rings in case of a lockup and with that should make a userspace
problem with a single application far less problematic.

The first four patches are just stuff this patchset is based upon, followed by
four patches which fix various bugs found while working on this feature.

Followed by patches which change the way how memory is saved/restored on
suspend/resume, basically before we have unpinned most of the buffer objects so
it could be move from vram into system memory. But that is mostly unnecessary
cause the buffer object either are already in system memory or their content
can be easily reinitialized.

The last three patches implement the actual tracking and restoring of commands
in case of a lockup. Please take a look and review.

Cheers,
Christian.