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drm/i915/bdw: poll semaphores

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As Ville points out, it's possible/probable we don't actually need this.
Potentially, this validates the letter of the spec, and not the spirit.

Ville:
> I discussed this on irc w/ Ben, and I was suggesting we don't need to
> poll. Polling apparently can be used as a workaround for certain
> hardware issues, but it looks like those issues shouldn't affect us,
> for the momemnt at least. So my suggestion was to try w/o polling
> first (since there could be some power cost to polling) and add the
> poll bit if problems arise.

Rodrigo: Spec suggests this as an W/A for GT3. However semaphores didn't
worked in my BDW GT2 on Signal Mode. So pool mode is definitely needed.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Tested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Ben Widawsky 2014-06-30 09:53:43 -07:00 committed by Daniel Vetter
parent e04934cf25
commit bae4fcd2c7
1 changed files with 1 additions and 0 deletions
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drivers/gpu/drm/i915/intel_ringbuffer.c
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@ -847,6 +847,7 @@ gen8_ring_sync(struct intel_engine_cs *waiter,
intel_ring_emit(waiter, MI_SEMAPHORE_WAIT |
MI_SEMAPHORE_GLOBAL_GTT |
MI_SEMAPHORE_POLL |
MI_SEMAPHORE_SAD_GTE_SDD);
intel_ring_emit(waiter, seqno);
intel_ring_emit(waiter,