drm/i915: Insert a command barrier on BLT/BSD cache flushes

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This looked like an odd regression from

commit ec5cc0f9b0
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Jun 12 10:28:55 2014 +0100

    drm/i915: Restrict GPU boost to the RCS engine

but in reality it undercovered a much older coherency bug. The issue that
boosting the GPU frequency on the BCS ring was masking was that we could
wake the CPU up after completion of a BCS batch and inspect memory prior
to the write cache being fully evicted. In order to serialise the
breadcrumb interrupt (and so ensure that the CPU's view of memory is
coherent) we need to perform a post-sync operation in the MI_FLUSH_DW.

v2: Fix all the MI_FLUSH_DW (bsd plus the duplication in execlists).

Also fix the invalidate_domains mask in gen8_emit_flush() for ring !=
VCS.

Testcase: gpuX-rcs-gpu-read-after-write
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

...

This commit is contained in:

Chris Wilson 2015-01-22 13:42:00 +00:00 • committed by Jani Nikula

parent 0ca0968554

commit f0a1fb10e5

2 changed files with 30 additions and 13 deletions

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20

drivers/gpu/drm/i915/intel_lrc.c

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23

drivers/gpu/drm/i915/intel_ringbuffer.c

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