drm/i915/icl: initialize MBus during display init

This patch initializes MBus during display initialization.

Changes since V2 (from Paulo):
 - Don't forget to remove the WARN_ON(1) call.
Changes since V1:
 - Rebase to use function like Macros
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: James Ausmus <james.ausmus@intel.com>
Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180205154046.11485-6-paulo.r.zanoni@intel.com

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -2676,6 +2676,18 @@ static void icl_dbuf_disable(struct drm_i915_private *dev_priv)
 		DRM_ERROR("DBuf power disable timeout!\n");
 }
 
+static void icl_mbus_init(struct drm_i915_private *dev_priv)
+{
+	uint32_t val;
+
+	val = MBUS_ABOX_BT_CREDIT_POOL1(16) |
+	      MBUS_ABOX_BT_CREDIT_POOL2(16) |
+	      MBUS_ABOX_B_CREDIT(1) |
+	      MBUS_ABOX_BW_CREDIT(1);
+
+	I915_WRITE(MBUS_ABOX_CTL, val);
+}
+
 static void skl_display_core_init(struct drm_i915_private *dev_priv,
 				   bool resume)
 {
@@ -2990,7 +3002,7 @@ static void icl_display_core_init(struct drm_i915_private *dev_priv,
 	icl_dbuf_enable(dev_priv);
 
 	/* 7. Setup MBUS. */
-	/* FIXME: MBUS code not here yet. */
+	icl_mbus_init(dev_priv);
 
 	/* 8. CHICKEN_DCPR_1 */
 	I915_WRITE(GEN8_CHICKEN_DCPR_1, I915_READ(GEN8_CHICKEN_DCPR_1) |