drm/i915: Mimic skl with WaForceEnableNonCoherent

Past evidence with system hangs and hsds tie
WaForceEnableNonCoherent and WaDisableHDCInvalidation to
WaForceContextSaveRestoreNonCoherent. Documentation
states that WaForceContextSaveRestoreNonCoherent would
not be needed on skl past E0 but evidence proved otherwise. See
commit <510650e8> ("drm/i915/skl: Fix spurious gpu hang with gt3/gt4
revs"). In this scope consider kbl to be skl with a bigger revision than
E0 so play it safe and bind these two workarounds to the
WaForceContextSaveRestoreNonCoherent, and apply to all gen9.

v2: fix comment (Matthew)

References: HSD#2134449, HSD#2131413
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-7-git-send-email-mika.kuoppala@intel.com

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -972,6 +972,27 @@ static int gen9_init_workarounds(struct intel_engine_cs *engine)
 			  HDC_FORCE_CONTEXT_SAVE_RESTORE_NON_COHERENT |
 			  HDC_FORCE_CSR_NON_COHERENT_OVR_DISABLE);
 
+	/* WaForceEnableNonCoherent and WaDisableHDCInvalidation are
+	 * both tied to WaForceContextSaveRestoreNonCoherent
+	 * in some hsds for skl. We keep the tie for all gen9. The
+	 * documentation is a bit hazy and so we want to get common behaviour,
+	 * even though there is no clear evidence we would need both on kbl/bxt.
+	 * This area has been source of system hangs so we play it safe
+	 * and mimic the skl regardless of what bspec says.
+	 *
+	 * Use Force Non-Coherent whenever executing a 3D context. This
+	 * is a workaround for a possible hang in the unlikely event
+	 * a TLB invalidation occurs during a PSD flush.
+	 */
+
+	/* WaForceEnableNonCoherent:skl,bxt,kbl */
+	WA_SET_BIT_MASKED(HDC_CHICKEN0,
+			  HDC_FORCE_NON_COHERENT);
+
+	/* WaDisableHDCInvalidation:skl,bxt,kbl */
+	I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) |
+		   BDW_DISABLE_HDC_INVALIDATION);
+
 	/* WaDisableSamplerPowerBypassForSOPingPong:skl,bxt,kbl */
 	if (IS_SKYLAKE(dev_priv) ||
 	    IS_KABYLAKE(dev_priv) ||
@@ -1089,22 +1110,6 @@ static int skl_init_workarounds(struct intel_engine_cs *engine)
 		WA_SET_BIT_MASKED(HIZ_CHICKEN,
 				  BDW_HIZ_POWER_COMPILER_CLOCK_GATING_DISABLE);
 
-	/* This is tied to WaForceContextSaveRestoreNonCoherent */
-	if (IS_SKL_REVID(dev_priv, 0, REVID_FOREVER)) {
-		/*
-		 *Use Force Non-Coherent whenever executing a 3D context. This
-		 * is a workaround for a possible hang in the unlikely event
-		 * a TLB invalidation occurs during a PSD flush.
-		 */
-		/* WaForceEnableNonCoherent:skl */
-		WA_SET_BIT_MASKED(HDC_CHICKEN0,
-				  HDC_FORCE_NON_COHERENT);
-
-		/* WaDisableHDCInvalidation:skl */
-		I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) |
-			   BDW_DISABLE_HDC_INVALIDATION);
-	}
-
 	/* WaBarrierPerformanceFixDisable:skl */
 	if (IS_SKL_REVID(dev_priv, SKL_REVID_C0, SKL_REVID_D0))
 		WA_SET_BIT_MASKED(HDC_CHICKEN0,