drm/i915: "Flush Me Harder" required on gen6+
The prep to remove the flushing list in commit cc889e0f Author: Daniel Vetter <daniel.vetter@ffwll.ch> Date: Wed Jun 13 20:45:19 2012 +0200 drm/i915: disable flushing_list/gpu_write_list causes quite some decent regressions. We can fix this by setting the CS_STALL bit to ensure that the following seqno write happens only after the cache flush has completed. But only do that when the caller actually wants the flush (and not also when we invalidate caches before starting the next batch). I've looked through all our ancient scrolls about gen6+ pipe control workarounds, and this seems to be indeed a legal combination: We're allowed to set the CS_STALL bit when we flush the render cache (which we do). While yelling at this code, also pass back the return value from intel_emit_post_sync_nonzero_flush properly. v2: Instead of emitting more pipe controls, set the CS_STALL bit on the write flush as suggested by Chris Wilson. It seems to work, too. Cc: Eric Anholt <eric@anholt.net> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51436 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51429 Tested-by: Lu Hua <huax.lu@intel.com> Tested-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
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