Created attachment 128323 [details]
logged using netconsole - kernel 4.8.7 (Debian kernel)

Dear developers,
I'm unable to boot into functional system with KMS radeon. When
radeon.modeset=0 on kernel command-line system it starts and run OK.
Without disabled modeset the kernel 4.7, 4.8, 4.9-rc7 with 90% probability
locks or crash.
I'm running Debian unstable and tried Debian kernels 4.7, 4.8 from Debian and
compile 4.9rc7 vanilla kernel.

Attached logs through netconsole.

Any idea what I can test?

Thanks
-- 
Zito

ref: debian bug #845382 -
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=845382