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drm/i915/gt: Try an extra flush on the Haswell blitter

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On gen7, including Haswell, the MI_FLUSH_DW command is not synchronous
with the command streamer nor is there an option to make it so. To hide
this we add a large delay on the CS so that the breadcrumb should always
be visible before the interrupt. However, that does not seem to be
enough to ensure the memory is actually coherent with the read of the
breadcrumb. The breadcrumb update is a post-sync op... Throw in a
preliminary MI_FLUSH_DW before the breadcrumb update in the hope that
helps.

References: https://bugs.freedesktop.org/show_bug.cgi?id=112147
Testcase: igt/i915_selftest/live_blt
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191111120957.17732-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2019-11-11 12:09:57 +00:00
parent b5b61cb4b1
commit f9228f7658
1 changed files with 4 additions and 1 deletions
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5
drivers/gpu/drm/i915/gt/intel_ring_submission.c
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@ -454,6 +454,10 @@ static u32 *gen7_xcs_emit_breadcrumb(struct i915_request *rq, u32 *cs)
GEM_BUG_ON(i915_request_active_timeline(rq)->hwsp_ggtt != rq->engine->status_page.vma);
GEM_BUG_ON(offset_in_page(i915_request_active_timeline(rq)->hwsp_offset) != I915_GEM_HWS_SEQNO_ADDR);
*cs++ = MI_FLUSH_DW;
*cs++ = 0;
*cs++ = 0;
*cs++ = MI_FLUSH_DW | MI_FLUSH_DW_OP_STOREDW | MI_FLUSH_DW_STORE_INDEX;
*cs++ = I915_GEM_HWS_SEQNO_ADDR | MI_FLUSH_DW_USE_GTT;
*cs++ = rq->fence.seqno;
@ -469,7 +473,6 @@ static u32 *gen7_xcs_emit_breadcrumb(struct i915_request *rq, u32 *cs)
*cs++ = 0;
*cs++ = MI_USER_INTERRUPT;
*cs++ = MI_NOOP;
rq->tail = intel_ring_offset(rq, cs);
assert_ring_tail_valid(rq->ring, rq->tail);