https://bugzilla.kernel.org/show_bug.cgi?id=62721
--- Comment #11 from Alex Deucher alexdeucher@gmail.com --- (In reply to Andrew Dorney from comment #8)
I am also having a random lockup problem on my HD6850, with the same CP stall error. Running Mesa 10.0.1 and kernel 3.12.6 vanilla with radeon driver. Attached lspci and dmesg. I'll boot with DPM disabled for the rest of the week and see if that changes it.
This bug is about a GPU hang on an r5xx board. You issue is mostly likely completely unrelated. You issue looks like it may be a duplicate of bug 68571.