drm/i915/bdw: WaSingleSubspanDispatchOnAALinesAndPoints

Implement WaSingleSubspanDispatchOnAALinesAndPoints

BDW-A workaround.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -5001,6 +5001,7 @@
 #define GEN7_HALF_SLICE_CHICKEN1	0xe100 /* IVB GT1 + VLV */
 #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_PSD_SINGLE_PORT_DISPATCH_ENABLE	(1<<3)
 
 #define GEN7_ROW_CHICKEN2		0xe4f4

drivers/gpu/drm/i915/intel_pm.c

@@ -5300,6 +5300,9 @@ static void gen8_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(COMMON_SLICE_CHICKEN2,
 		   _MASKED_BIT_ENABLE(GEN8_CSC2_SBE_VUE_CACHE_CONSERVATIVE));
 
+	I915_WRITE(GEN7_HALF_SLICE_CHICKEN1,
+		   _MASKED_BIT_ENABLE(GEN7_SINGLE_SUBSCAN_DISPATCH_ENABLE));
+
 	/* WaSwitchSolVfFArbitrationPriority */
 	I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) | HSW_ECOCHK_ARB_PRIO_SOL);