[Intel-gfx] [PATCH 1/5] drm/i915: Always pin the fence for scanout on gen2/3 and primary planes

[Chris Wilson]

Quoting Ville Syrjala (2017-11-16 19:14:47)
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The current code is trying to be lazy with fences on scanout buffers.
> That looks broken for several reasons:
> * gen2/3 always need a fence for tiled scanout

Which it already gets. All gen2-gen4 are given a fenceable vma.

> * the unpin doesn't know whether we pinned the fence or not so it
>   may unpin something we don't own

Then track it correctly.

> * FBC GTT tracking needs a fence (not sure we have proper fallback
>   for when there is no fence)

Debatable as whether that is worth forcing a fence; the argument being
that you don't want to stall your flip upon eviction which is the
situation you are already in if you didn't get a fence in the first
place.
-Chris