drm/i915/skl: Implement WaDisableDgMirrorFixInHalfSliceChicken5:skl

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_reg.h

@@ -5866,6 +5866,9 @@ enum punit_power_well {
 #define   GEN7_SINGLE_SUBSCAN_DISPATCH_ENABLE	(1<<10)
 #define   GEN7_PSD_SINGLE_PORT_DISPATCH_ENABLE	(1<<3)
 
+#define GEN9_HALF_SLICE_CHICKEN5	0xe188
+#define   GEN9_DG_MIRROR_FIX_ENABLE	(1<<5)
+
 #define GEN8_ROW_CHICKEN		0xe4f0
 #define   PARTIAL_INSTRUCTION_SHOOTDOWN_DISABLE	(1<<8)
 #define   STALL_DOP_GATING_DISABLE		(1<<5)

drivers/gpu/drm/i915/intel_pm.c

@@ -77,6 +77,14 @@ static void gen9_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
 		   GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
 
+	/*
+	 * WaDisableDgMirrorFixInHalfSliceChicken5:skl
+	 * This is a pre-production w/a.
+	 */
+	I915_WRITE(GEN9_HALF_SLICE_CHICKEN5,
+		   I915_READ(GEN9_HALF_SLICE_CHICKEN5) &
+		   ~GEN9_DG_MIRROR_FIX_ENABLE);
+
 	/* Wa4x4STCOptimizationDisable:skl */
 	I915_WRITE(CACHE_MODE_1,
 		   _MASKED_BIT_ENABLE(GEN8_4x4_STC_OPTIMIZATION_DISABLE));