drm/i915: Don't set up DP ports that aren't in the BIOS device table.

Use the child device array to decide whether the given DP output should be
initialized. If the given DP port can't be found in child device array,
it is not present and won't be initialized.
Signed-off-by: NZhao Yakui <yakui.zhao@intel.com>
Signed-off-by: NEric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_dp.c

@@ -35,6 +35,7 @@
 #include "i915_drv.h"
 #include "intel_dp.h"
 
+
 #define DP_LINK_STATUS_SIZE	6
 #define DP_LINK_CHECK_TIMEOUT	(10 * 1000)
 
@@ -1228,7 +1229,53 @@ intel_dp_hot_plug(struct intel_output *intel_output)
 	if (dp_priv->dpms_mode == DRM_MODE_DPMS_ON)
 		intel_dp_check_link_status(intel_output);
 }
-
+/*
+ * Enumerate the child dev array parsed from VBT to check whether
+ * the given DP is present.
+ * If it is present, return 1.
+ * If it is not present, return false.
+ * If no child dev is parsed from VBT, it is assumed that the given
+ * DP is present.
+ */
+int dp_is_present_in_vbt(struct drm_device *dev, int dp_reg)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct child_device_config *p_child;
+	int i, dp_port, ret;
+
+	if (!dev_priv->child_dev_num)
+		return 1;
+
+	dp_port = 0;
+	if (dp_reg == DP_B || PCH_DP_B)
+		dp_port = PORT_IDPB;
+	else if (dp_reg == DP_C || PCH_DP_C)
+		dp_port = PORT_IDPC;
+	else if (dp_reg == DP_D || PCH_DP_D)
+		dp_port = PORT_IDPD;
+
+	ret = 0;
+	for (i = 0; i < dev_priv->child_dev_num; i++) {
+		p_child = dev_priv->child_dev + i;
+		/*
+		 * If the device type is not DP, continue.
+		 */
+		if (p_child->device_type != DEVICE_TYPE_DP &&
+			p_child->device_type != DEVICE_TYPE_eDP)
+			continue;
+		/* Find the eDP port */
+		if (dp_reg == DP_A && p_child->device_type == DEVICE_TYPE_eDP) {
+			ret = 1;
+			break;
+		}
+		/* Find the DP port */
+		if (p_child->dvo_port == dp_port) {
+			ret = 1;
+			break;
+		}
+	}
+	return ret;
+}
 void
 intel_dp_init(struct drm_device *dev, int output_reg)
 {
@@ -1238,6 +1285,10 @@ intel_dp_init(struct drm_device *dev, int output_reg)
 	struct intel_dp_priv *dp_priv;
 	const char *name = NULL;
 
+	if (!dp_is_present_in_vbt(dev, output_reg)) {
+		DRM_DEBUG_KMS("DP is not present. Ignore it\n");
+		return;
+	}
 	intel_output = kcalloc(sizeof(struct intel_output) + 
 			       sizeof(struct intel_dp_priv), 1, GFP_KERNEL);
 	if (!intel_output)