you might try loading the radeon drm with new_pll=0 or try this patch: http://git.kernel.org/?p=linux/kernel/git/airlied/drm-2.6.git;a=commit;h=383be5d1789d9a7a2e77dca1cb0aca89507d069e if your drm doesn't already have it.
you might try loading the radeon drm with new_pll=0 or try this patch: git.kernel. org/?p= linux/kernel/ git/airlied/ drm-2.6. git;a=commit; h=383be5d1789d9 a7a2e77dca1cb0a ca89507d069e
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if your drm doesn't already have it.