[PATCH v11 4/5] drm/msm/dp: parser link-frequencies as property of dp_out endpoint

[Kuogee Hsieh]

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)

Signed-off-by: Kuogee Hsieh <quic_khs...@quicinc.com>
---
 drivers/gpu/drm/msm/dp/dp_parser.c | 27 +++++++++++++++++++++++++++
 drivers/gpu/drm/msm/dp/dp_parser.h |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c 
b/drivers/gpu/drm/msm/dp/dp_parser.c
index b5f7e70..9a7dcd4 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.c
+++ b/drivers/gpu/drm/msm/dp/dp_parser.c
@@ -91,6 +91,29 @@ 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 = 0;
+
+       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);
+
+       frequency /= 10;        /* from symbol rate to link rate */
+       frequency /= 1000;      /* kbytes */
+
+       return frequency;
+}
+
 static int dp_parser_misc(struct dp_parser *parser)
 {
        struct device_node *of_node = parser->pdev->dev.of_node;
@@ -113,6 +136,10 @@ static int dp_parser_misc(struct dp_parser *parser)
                        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; /* 540000 khz */
+
        return 0;
 }
 
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h 
b/drivers/gpu/drm/msm/dp/dp_parser.h
index 866c1a8..6b10c3e 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.h
+++ b/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 /* khz */
 
 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);
-- 
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