[Intel-gfx] [PATCH] drm/i915: Disable SAMPLER_STATE prefetching on all Gen11 steppings.

[Chris Wilson]

From: Kenneth Graunke <kenneth at whitecape.org>

The Demand Prefetch workaround (binding table prefetching) only applies
to Icelake A0/B0.  But the Sampler Prefetch workaround needs to be
applied to all Gen11 steppings, according to a programming note in the
SARCHKMD documentation.

Using the Intel Gallium driver, I have seen intermittent failures in
the dEQP-GLES31.functional.copy_image.non_compressed.* tests.  After
applying this workaround, the tests reliably pass.

v2: Remove the overlap with a pre-production w/a

BSpec: 9663
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/i915/gt/intel_workarounds.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
index c70445adfb02..993804d09517 100644
--- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
@@ -1252,8 +1252,12 @@ rcs_engine_wa_init(struct intel_engine_cs *engine, struct i915_wa_list *wal)
 		if (IS_ICL_REVID(i915, ICL_REVID_A0, ICL_REVID_B0))
 			wa_write_or(wal,
 				    GEN7_SARCHKMD,
-				    GEN7_DISABLE_DEMAND_PREFETCH |
-				    GEN7_DISABLE_SAMPLER_PREFETCH);
+				    GEN7_DISABLE_DEMAND_PREFETCH);
+
+		/* Wa_1606682166:icl */
+		wa_write_or(wal,
+			    GEN7_SARCHKMD,
+			    GEN7_DISABLE_SAMPLER_PREFETCH);
 	}
 
 	if (IS_GEN_RANGE(i915, 9, 11)) {
-- 
2.20.1