drm/i915/bxt: Add WaDisableSbeCacheDispatchPortSharing

Note that we also need this for skl.
Signed-off-by: Nick Hoath <nicholas.hoath@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
[danvet: Note that we also need this for skl, requested by Imre.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -6738,6 +6738,7 @@ enum skl_disp_power_wells {
 #define GEN7_HALF_SLICE_CHICKEN1_GT2	0xf100
 #define   GEN7_MAX_PS_THREAD_DEP		(8<<12)
 #define   GEN7_SINGLE_SUBSCAN_DISPATCH_ENABLE	(1<<10)
+#define   GEN7_SBE_SS_CACHE_DISPATCH_PORT_SHARING_DISABLE	(1<<4)
 #define   GEN7_PSD_SINGLE_PORT_DISPATCH_ENABLE	(1<<3)
 
 #define GEN9_HALF_SLICE_CHICKEN5	0xe188

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1050,6 +1050,13 @@ static int bxt_init_workarounds(struct intel_engine_cs *ring)
 	WA_SET_BIT_MASKED(GEN8_ROW_CHICKEN,
 			  STALL_DOP_GATING_DISABLE);
 
+	/* WaDisableSbeCacheDispatchPortSharing:bxt */
+	if (INTEL_REVID(dev) <= BXT_REVID_B0) {
+		WA_SET_BIT_MASKED(
+			GEN7_HALF_SLICE_CHICKEN1,
+			GEN7_SBE_SS_CACHE_DISPATCH_PORT_SHARING_DISABLE);
+	}
+
 	return 0;
 }