https://bugs.freedesktop.org/show_bug.cgi?id=66963
--- Comment #33 from Scias shining.scias@gmail.com --- Sorry I'm a bit late. My tests are a little bit different from Sergey's.
Unpatched : Hangs 3/4 times - Unresponsive X - Setting battery state = corruption - "Frost" flicker at modeset
No clockgating : Same as unpatched
No voltage control : Hangs everytime
No PCIE2 : Hangs everytime
No dynamic spectrum : Boots everytime - X is okay - Setting battery state is okay - "Frost" flicker at modeset.
So clearly disabling the dynamic spectrum really helped for me. Another finding is that setting radeon in the initramfs (for early KMS) results in guaranteed hang except with disabled spectrum where it still boots everytime.