kernel -

fb240a2534802a86742db51b7334138675bc435e is the first bad commit
commit fb240a2534802a86742db51b7334138675bc435e
Author: Michel Dänzer <michel.daenzer@amd.com>
Date:   Thu Jul 31 18:43:49 2014 +0900

    drm/radeon: Always flush the HDP cache before submitting a CS to the GPU

    This ensures the GPU sees all previous CPU writes to VRAM, which makes it
    safe:

    * For userspace to stream data from CPU to GPU via VRAM instead of GTT
    * For IBs to be stored in VRAM instead of GTT
    * For ring buffers to be stored in VRAM instead of GTT, if the HPD flush
      is performed via MMIO

    Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>