linux-kernel - [PATCH v14 4/5] drm/msm/dp: parse link-frequencies as property of dp

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Date:   Fri, 16 Dec 2022 11:11:32 -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>, <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 v14 4/5] drm/msm/dp: parse 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

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@...cinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
---
 drivers/gpu/drm/msm/dp/dp_parser.c | 28 ++++++++++++++++++++++++++++
 drivers/gpu/drm/msm/dp/dp_parser.h |  2 ++
 2 files changed, 30 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
index d42987a..21ba40d 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.c
+++ b/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;
@@ -113,6 +137,10 @@ 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;
+
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h b/drivers/gpu/drm/msm/dp/dp_parser.h
index 866c1a8..526131ee 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 /* 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);
-- 
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