drm/msm/dp: Add capability to parser and retrieve max DP link supported rate...

drm/msm/dp: Add capability to parser and retrieve max DP link supported rate from link-frequencies property of dp_out endpoint

Changes in v6:
-- second patch after split parser patch into two patches

Changes in v7:
-- without checking cnt against DP_MAX_NUM_DP_LANES to retrieve link rate

Changes in v9:
-- separate parser link-frequencies out of data-lanes

Changes in v10:
-- add dp_parser_link_frequencies()

Changes in v11:
-- return 0 if(!endpoint)

Changes in v12:
-- replace khz with kbytes at dp_parser.h

Changes in v14:
-- replace "parser" with "parse" at commit subject
-- use do_div() for 64 bits division
Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/516100/
Link: https://lore.kernel.org/r/1672163103-31254-5-git-send-email-quic_khsieh@quicinc.comSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

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

@@ -91,6 +91,30 @@ static int dp_parser_ctrl_res(struct dp_parser *parser)
 	return 0;
 }
 
+static u32 dp_parser_link_frequencies(struct device_node *of_node)
+{
+	struct device_node *endpoint;
+	u64 frequency = 0;
+	int cnt;
+
+	endpoint = of_graph_get_endpoint_by_regs(of_node, 1, 0); /* port@1 */
+	if (!endpoint)
+		return 0;
+
+	cnt = of_property_count_u64_elems(endpoint, "link-frequencies");
+
+	if (cnt > 0)
+		of_property_read_u64_index(endpoint, "link-frequencies",
+						cnt - 1, &frequency);
+	of_node_put(endpoint);
+
+	do_div(frequency,
+		10 * /* from symbol rate to link rate */
+		1000); /* kbytes */
+
+	return frequency;
+}
+
 static int dp_parser_misc(struct dp_parser *parser)
 {
 	struct device_node *of_node = parser->pdev->dev.of_node;
@@ -110,6 +134,10 @@ static int dp_parser_misc(struct dp_parser *parser)
 	else
 		parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */
 
+	parser->max_dp_link_rate = dp_parser_link_frequencies(of_node);
+	if (!parser->max_dp_link_rate)
+		parser->max_dp_link_rate = DP_LINK_RATE_HBR2;
+
 	return 0;
 }
 

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

@@ -15,6 +15,7 @@
 #define DP_LABEL "MDSS DP DISPLAY"
 #define DP_MAX_PIXEL_CLK_KHZ	675000
 #define DP_MAX_NUM_DP_LANES	4
+#define DP_LINK_RATE_HBR2	540000 /* kbytes */
 
 enum dp_pm_type {
 	DP_CORE_PM,
@@ -119,6 +120,7 @@ struct dp_parser {
 	struct dp_io io;
 	struct dp_display_data disp_data;
 	u32 max_dp_lanes;
+	u32 max_dp_link_rate;
 	struct drm_bridge *next_bridge;
 
 	int (*parse)(struct dp_parser *parser);