drm/msm/dp: parse data-lanes as property of dp_out endpoint

Add capability to parser data-lanes as property of dp_out endpoint.
Also retain the original capability to parser data-lanes as property
of mdss_dp node to handle legacy case.

Changes in v6:
-- first patch after split parser patch into two

Changes in v7:
-- check "data-lanes" from endpoint first

Changes in v14:
-- replace "parser" with "parse" at commit subject
-- add matching brackets at dp_parser_misc()

Changes in v15:
-- concise dp_parser_misc()
Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/516096/
Link: https://lore.kernel.org/r/1672163103-31254-4-git-send-email-quic_khsieh@quicinc.comSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/dp/dp_parser.c

@@ -94,16 +94,22 @@ static int dp_parser_ctrl_res(struct dp_parser *parser)
 static int dp_parser_misc(struct dp_parser *parser)
 {
 	struct device_node *of_node = parser->pdev->dev.of_node;
-	int len;
-
-	len = drm_of_get_data_lanes_count(of_node, 1, DP_MAX_NUM_DP_LANES);
-	if (len < 0) {
-		DRM_WARN("Invalid property \"data-lanes\", default max DP lanes = %d\n",
-			 DP_MAX_NUM_DP_LANES);
-		len = DP_MAX_NUM_DP_LANES;
+	int cnt;
+
+	/*
+	 * data-lanes is the property of dp_out endpoint
+	 */
+	cnt = drm_of_get_data_lanes_count_ep(of_node, 1, 0, 1, DP_MAX_NUM_DP_LANES);
+	if (cnt < 0) {
+		/* legacy code, data-lanes is the property of mdss_dp node */
+		cnt = drm_of_get_data_lanes_count(of_node, 1, DP_MAX_NUM_DP_LANES);
 	}
 
-	parser->max_dp_lanes = len;
+	if (cnt > 0)
+		parser->max_dp_lanes = cnt;
+	else
+		parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */
+
 	return 0;
 }