(In reply to Ernst Sj��strand from comment #1)
> There is a backtrace but no result of any bisect...?

I confirm the bisection section, see bug 94025.
294ec530c9829aead97487b1feb06361ef97cc2d is the first bad commit
commit 294ec530c9829aead97487b1feb06361ef97cc2d
Author: Marek Ol����k <marek.olsak@amd.com>
Date:   Sat Jan 30 01:52:58 2016 +0100

    gallium/radeon: just get num_tile_pipes from the winsys

    Reviewed-by: Michel D��nzer <michel.daenzer@amd.com>

:040000 040000 71cb2da01a5912443f2ca74f97e46533f50f50d8
964978b8372e95f18eb09db4158b032bf25611fb M    src

New way of setting num_pipes gives a value of 12, while previous was giving a
value of 8 on a R9 280X.