amdgpu_ring_get_dw_distance
amdgpu_ring_get_dw_distance(ring, vm_af->ib_wptr, ring->wptr);
amdgpu_ring_get_dw_distance(ring, af->ib_wptr, ring->wptr);
amdgpu_ring_get_dw_distance(ring, af->ib_wptr, ring->wptr);
af->ib_dw_size = amdgpu_ring_get_dw_distance(ring, af->ib_wptr, ring->wptr);
ring->ring[offset] = amdgpu_ring_get_dw_distance(ring, offset, ring->wptr - 1);