This is the result of the bisect. Unfortunately I had to skip some kernels because they wouldn't compile.
2099810f903caa1920f3ef6014fb7f36e4786490 is the first bad commit
Author: Dave Airlie <email address hidden>
Date: Tue Apr 3 11:53:05 2012 +0100
drm/radeon: enable pci bus mastering after card is initialised (v2)
This closes a race seen with kexec where we enable PCI bus mastering
but the card has been reinitialised fully yet.
This was previously fixed by a patch from Jerome, but this should
close the race completely.
v2: add SI support as suggested by Alex.
Reported-and-tested-by: Markus Trippelsdorf <email address hidden>
Signed-off-by: Dave Airlie <email address hidden>
:040000 040000 543c4ab332c9e62bf964d005f42e918160508777 73177e660b0ebca43b6a449bc208d7c8b00ab8c8 M drivers