[Intel-gfx] [PATCH 5/7] drm/i915: Add timeline barrier support

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-09-05 15:22:20)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Timeline barrier allows serialization between different timelines.
> 
> After calling i915_timeline_set_barrier with a request, all following
> submissions on this timeline will be set up as depending on this request,
> or barrier. Once the barrier has been completed it automatically gets
> cleared and things continue as normal.
> 
> This facility will be used by the upcoming context SSEU code.
> 
> v2:
>  * Assert barrier has been retired on timeline_fini. (Chris Wilson)
>  * Fix mock_timeline.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Suggested-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

I really should follow through on my threat to move
switch_to_kernel_context over to a similar scheme.
-Chris