linux-kernel - [PATCH v8 4/5] drm/msm/dp: parser link-frequencies as property of dp

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Message-ID: <1670267670-15832-5-git-send-email-quic_khsieh@quicinc.com>
Date:   Mon, 5 Dec 2022 11:14:29 -0800
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     <dri-devel@...ts.freedesktop.org>, <robdclark@...il.com>,
        <sean@...rly.run>, <swboyd@...omium.org>, <dianders@...omium.org>,
        <vkoul@...nel.org>, <daniel@...ll.ch>, <airlied@...ux.ie>,
        <agross@...nel.org>, <dmitry.baryshkov@...aro.org>,
        <andersson@...nel.org>, <konrad.dybcio@...ainline.org>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <devicetree@...r.kernel.org>, <airlied@...il.com>
CC:     Kuogee Hsieh <quic_khsieh@...cinc.com>,
        <quic_abhinavk@...cinc.com>, <quic_sbillaka@...cinc.com>,
        <freedreno@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v8 4/5] drm/msm/dp: parser link-frequencies as property of dp_out endpoint

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

Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
---
 drivers/gpu/drm/msm/dp/dp_parser.c | 19 +++++++++++++++++--
 drivers/gpu/drm/msm/dp/dp_parser.h |  2 ++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
index b5f7e70..037dad8 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.c
+++ b/drivers/gpu/drm/msm/dp/dp_parser.c
@@ -94,15 +94,28 @@ 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;
+	struct device_node *endpoint;
+	u64 frequency;
 	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)
+	if (cnt > 0) {
 		parser->max_dp_lanes = cnt;
-	else {
+
+		endpoint = of_graph_get_endpoint_by_regs(of_node, 1, 0); /* port@1 */
+		cnt = of_property_count_u64_elems(endpoint, "link-frequencies");
+		if (cnt > 0) {
+			of_property_read_u64_index(endpoint, "link-frequencies",
+							cnt - 1, &frequency);
+			frequency /= 10;	/* from symbol rate to link rate */
+			parser->max_dp_link_rate = (frequency / 1000); /* kbits */
+		} else {
+			parser->max_dp_link_rate = DP_LINK_RATE_HBR2; /* 540000 khz */
+		}
+	} else {
 		/*
 		 * legacy code, data-lanes is the property of mdss_dp node
 		 */
@@ -111,6 +124,8 @@ static int dp_parser_misc(struct dp_parser *parser)
 			parser->max_dp_lanes = cnt;
 		else
 			parser->max_dp_lanes = DP_MAX_NUM_DP_LANES; /* 4 lanes */
+
+		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..3ddf639 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
 
 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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