drm/i915/bdw: Limit SDE poly depth FIFO to 2

BDW-A workaround

BDW Bug #1899155
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -783,6 +783,7 @@
 #define _3D_CHICKEN3	0x02090
 #define  _3D_CHICKEN_SF_DISABLE_OBJEND_CULL		(1 << 10)
 #define  _3D_CHICKEN3_SF_DISABLE_FASTCLIP_CULL		(1 << 5)
+#define  _3D_CHICKEN_SDE_LIMIT_FIFO_POLY_DEPTH(x)	((x)<<1)
 
 #define MI_MODE		0x0209c
 # define VS_TIMER_DISPATCH				(1 << 6)

drivers/gpu/drm/i915/intel_pm.c

@@ -5294,6 +5294,9 @@ static void gen8_init_clock_gating(struct drm_device *dev)
 		   _MASKED_BIT_ENABLE(GEN8_SAMPLER_POWER_BYPASS_DIS));
 	I915_WRITE(GAMTARBMODE, _MASKED_BIT_ENABLE(ARB_MODE_BWGTLB_DISABLE));
 
+	I915_WRITE(_3D_CHICKEN3,
+		   _3D_CHICKEN_SDE_LIMIT_FIFO_POLY_DEPTH(2));
+
 	/* WaSwitchSolVfFArbitrationPriority */
 	I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) | HSW_ECOCHK_ARB_PRIO_SOL);