[Intel-gfx] [PATCH] drm/i915/gt: More delays for gen7 flushing

[Chris Wilson]

live_blt is still failing on hsw, showing the hallmark of incoherency.
Since we are fairly certain that the interrupt is after the seqno is
visible, the other possibility is that the seqno is before the writes to
memory are flushed. Throw in some more MI_FLUSH_DW before the breadcrumb
to try and flush any internal pipelines.

References: f9228f765873 ("drm/i915/gt: Try an extra flush on the Haswell blitter")
References: https://bugs.freedesktop.org/show_bug.cgi?id=112147
Testcase: igt/i915_selftest/live_blt
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_ring_submission.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
index fc29df712810..14d115891ed9 100644
--- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
@@ -454,9 +454,11 @@ 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;
+	for (i = 0; i < 7; i++) {
+		*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;
-- 
2.24.0