• John Harrison's avatar
    drm/i915: Reserve space improvements · 79bbcc29
    John Harrison authored
    An earlier patch was added to reserve space in the ring buffer for the
    commands issued during 'add_request()'. The initial version was
    pessimistic in the way it handled buffer wrapping and would cause
    premature wraps and thus waste ring space.
    
    This patch updates the code to better handle the wrap case. It no
    longer enforces that the space being asked for and the reserved space
    are a single contiguous block. Instead, it allows the reserve to be on
    the far end of a wrap operation. It still guarantees that the space is
    available so when the wrap occurs, no wait will happen. Thus the wrap
    cannot fail which is the whole point of the exercise.
    
    Also fixed a merge failure with some comments from the original patch.
    
    v2: Incorporated suggestion by David Gordon to move the wrap code
    inside the prepare function and thus allow a single combined
    wait_for_space() call rather than doing one before the wrap and
    another after. This also makes the prepare code much simpler and
    easier to follow.
    
    v3: Fix for 'effective_size' vs 'size' during ring buffer remainder
    calculations (spotted by Tomas Elf).
    
    For: VIZ-5115
    CC: Daniel Vetter <daniel@ffwll.ch>
    Signed-off-by: default avatarJohn Harrison <John.C.Harrison@Intel.com>
    Reviewed-by: default avatarTomas Elf <tomas.elf@intel.com>
    Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    79bbcc29
intel_ringbuffer.c 81.4 KB