[Intel-gfx] [PATCH v2] drm/i915: use semaphores for the display plane

Daniel Vetter daniel at ffwll.ch
Tue Apr 10 12:04:11 CEST 2012

On Thu, Apr 05, 2012 at 02:47:36PM -0700, Ben Widawsky wrote:
> 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.
> CC: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
Queued for -next (with Chris' irc r-b added), thanks for the patch.
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48

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