drm/i915/bdw: WaDisableFenceDestinationToSLM

This WA affect BDW GT3 pre-production steppings.
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
[danvet: Don't mention steppings ...]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -4836,6 +4836,7 @@ enum punit_power_well {
 /* GEN8 chicken */
 #define HDC_CHICKEN0				0x7300
 #define  HDC_FORCE_NON_COHERENT			(1<<4)
+#define  HDC_FENCE_DEST_SLM_DISABLE		(1<<14)
 
 /* WaCatErrorRejectionIssue */
 #define GEN7_SQ_CHICKEN_MBCUNIT_CONFIG		0x9030

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -740,8 +740,12 @@ static int bdw_init_workarounds(struct intel_engine_cs *ring)
 	 * workaround for for a possible hang in the unlikely event a TLB
 	 * invalidation occurs during a PSD flush.
 	 */
+	/* WaDisableFenceDestinationToSLM:bdw (GT3 pre-production) */
 	intel_ring_emit_wa(ring, HDC_CHICKEN0,
-			   _MASKED_BIT_ENABLE(HDC_FORCE_NON_COHERENT));
+			   _MASKED_BIT_ENABLE(HDC_FORCE_NON_COHERENT |
+					      (IS_BDW_GT3(dev) ?
+					       HDC_FENCE_DEST_SLM_DISABLE : 0)
+				   ));
 
 	/* Wa4x4STCOptimizationDisable:bdw */
 	intel_ring_emit_wa(ring, CACHE_MODE_1,