This commit [root at raven linux]# git bisect bad c704d7a15d292e6e222b7e990ed7e9f41617cdd8 is the first bad commit commit c704d7a15d292e6e222b7e990ed7e9f41617cdd8 Author: Alex Deucher <alexander.deucher at amd.com> Date: Tue Mar 27 17:10:56 2018 -0500 drm/amdgpu/gmc9: use amdgpu_ring_emit_reg_write_reg_wait in gpu tlb flush Use amdgpu_ring_emit_reg_write_reg_wait. On engines that support it, it provides a write and wait in a single packet which avoids a missed ack if a world switch happens between the request and waiting for the ack. Reviewed-by: Huang Rui <ray.huang at amd.com> Reviewed-by: Christian König <christian.koenig at amd.com> Signed-off-by: Alex Deucher <alexander.deucher at amd.com> :040000 040000 a08a12a316d09ea231337136cc7aa076d4da44a8 521c8a18b0c63e185e416a267619a92822d7f268 M drivers Causes my raven1 to lockup on starting X with a gfx ring stall. Tom