• Ben Widawsky's avatar
    drm/i915: use semaphores for the display plane · 2911a35b
    Ben Widawsky authored
    
    
    In theory this will have performance and power improvements. Performance
    because we don't need to stall when the scanout BO is busy, and power
    because we don't have to stall when the BO is busy (and the ring can
    even go to sleep if the HW supports it).
    
    v2:
    squash 2 patches into 1 (me)
    un-inline the enable_semaphores function (Daniel)
    remove comment about SNB hangs from i915_gem_object_sync (Chris)
    rename intel_enable_semaphores to i915_semaphore_is_enabled (me)
    removed page flip comment; "no why" (Chris)
    
    To address other comments from Daniel (irc):
    update the comment to say 'vt-d is crap, don't enable semaphores'
      - I think you misinterpreted Chris' comment, it already exists.
    checking out whether we can pageflip on the render ring on ivb (didn't
    work on early silicon)
      - We don't want to enable workarounds for early silicon unless we have
        to.
      - I can't find any references in the docs about this.
    optionally use it if the fb is already busy on the render ring
      - This should be how the code already worked, unless I am
        misunderstanding your meaning.
    
    Signed-off-by: default avatarBen Widawsky <ben@bwidawsk.net>
    Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    2911a35b