Fedora kernel bisect advice?

[Bruno Wolff III]

On Wed, Sep 25, 2013 at 10:35:43 -0500,
   "Justin M. Forbes" <jforbes at fedoraproject.org> wrote:
>
>Josh was recommending you skip building at all and test kernels which
>koji already built.  The rawhide kernels are build very frequently and
>can help narrow down the range. That said, if it is a radeon problem,
>the radeon firmware was also updated with 3.11 so it might not
>specifically be a kernel commit.

That part I already did. It happened between 3.12-rc0.git22 and 3.12-rc0-git24. 
(git23 failed to build). I need to use radeon.agpmode=-1 in order to work 
around an old bug affecting rv280s. However that starting causing the 
device to not be recognized as being able to do KMS which is prevent X 
from working. If I leave the option off, I get X, but the console
mostly locks up within a few minutes. Since the old bug is pretty old 
now I think trying to use those kernels on a current Fedora would be 
problematic, so I am trying to do a bisect for the more recent issue. 
If this goes well, I might try to go back and do the other one, but it 
is about three years old.