drm/i915/bxt: add WaDisableMaskBasedCammingInRCC workaround

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Nick Hoath <nicholas.hoath@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -5346,6 +5346,10 @@ enum skl_disp_power_wells {
 #define  HDC_FORCE_NON_COHERENT			(1<<4)
 #define  HDC_BARRIER_PERFORMANCE_DISABLE	(1<<10)
 
+/* GEN9 chicken */
+#define SLICE_ECO_CHICKEN0			0x7308
+#define   PIXEL_MASK_CAMMING_DISABLE		(1 << 14)
+
 /* WaCatErrorRejectionIssue */
 #define GEN7_SQ_CHICKEN_MBCUNIT_CONFIG		0x9030
 #define  GEN7_SQ_CHICKEN_MBCUNIT_SQINTMOB	(1<<11)

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -966,6 +966,15 @@ static int gen9_init_workarounds(struct intel_engine_cs *ring)
 	WA_CLR_BIT_MASKED(GEN9_HALF_SLICE_CHICKEN5,
 			  GEN9_CCS_TLB_PREFETCH_ENABLE);
 
+	/*
+	 * FIXME: don't apply the following on BXT for stepping C. On BXT A0
+	 * the flag reads back as 0.
+	 */
+	/* WaDisableMaskBasedCammingInRCC:bxtA */
+	if (IS_BROXTON(dev))
+		WA_SET_BIT_MASKED(SLICE_ECO_CHICKEN0,
+				  PIXEL_MASK_CAMMING_DISABLE);
+
 	return 0;
 }