drm/i915: Only insert the mb() before updating the fence parameter

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With a fence, we only need to insert a memory barrier around the actual
fence alteration for CPU accesses through the GTT. Performing the
barrier in flush-fence was inserting unnecessary and expensive barriers
for never fenced objects.

Note removing the barriers from flush-fence, which was effectively a
barrier before every direct access through the GTT, revealed that we
where missing a barrier before the first access through the GTT. Lack of
that barrier was sufficient to cause GPU hangs.

v2: Add a couple more comments to explain the new barriers

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

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Chris Wilson 2012-10-09 19:24:37 +01:00 • committed by Daniel Vetter

parent 1f83fee08d

commit d0a57789d5

1 changed files with 30 additions and 10 deletions

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drivers/gpu/drm/i915/i915_gem.c

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