linux-kernel - [PATCH v2 2/2] drm/msm/dp: add supported max link rate specified from dtsi

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Date:   Thu, 18 Feb 2021 12:55:04 -0800
From:   Kuogee Hsieh <khsieh@...eaurora.org>
To:     robdclark@...il.com, sean@...rly.run, swboyd@...omium.org
Cc:     tanmay@...eaurora.org, abhinavk@...eaurora.org,
        aravindh@...eaurora.org, khsieh@...eaurora.org, airlied@...ux.ie,
        daniel@...ll.ch, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] drm/msm/dp: add supported max link rate specified from dtsi

Allow supported link rate to be limited to the value specified at
dtsi. If it is not specified, then link rate is derived from dpcd
directly. Below are examples,
link-rate = <162000> for max link rate limited at 1.62G
link-rate = <270000> for max link rate limited at 2.7G
link-rate = <540000> for max link rate limited at 5.4G
link-rate = <810000> for max link rate limited at 8.1G

Changes in V2:
-- allow supported max link rate specified from dtsi

Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
---
 drivers/gpu/drm/msm/dp/dp_display.c |  1 +
 drivers/gpu/drm/msm/dp/dp_panel.c   |  7 ++++---
 drivers/gpu/drm/msm/dp/dp_panel.h   |  1 +
 drivers/gpu/drm/msm/dp/dp_parser.c  | 13 +++++++++++++
 drivers/gpu/drm/msm/dp/dp_parser.h  |  1 +
 5 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 5a39da6..f633ba6 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -322,6 +322,7 @@ static int dp_display_process_hpd_high(struct dp_display_private *dp)
 	struct edid *edid;
 
 	dp->panel->max_dp_lanes = dp->parser->max_dp_lanes;
+	dp->panel->max_link_rate = dp->parser->max_link_rate;
 
 	rc = dp_panel_read_sink_caps(dp->panel, dp->dp_display.connector);
 	if (rc)
diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
index 9cc8166..be7f102 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.c
+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
@@ -76,9 +76,10 @@ static int dp_panel_read_dpcd(struct dp_panel *dp_panel)
 	if (link_info->num_lanes > dp_panel->max_dp_lanes)
 		link_info->num_lanes = dp_panel->max_dp_lanes;
 
-	/* Limit support upto HBR2 until HBR3 support is added */
-	if (link_info->rate >= (drm_dp_bw_code_to_link_rate(DP_LINK_BW_5_4)))
-		link_info->rate = drm_dp_bw_code_to_link_rate(DP_LINK_BW_5_4);
+	/* Limit support of ink rate if specified */
+	if (dp_panel->max_link_rate &&
+			(link_info->rate > dp_panel->max_link_rate))
+		link_info->rate = dp_panel->max_link_rate;
 
 	DRM_DEBUG_DP("version: %d.%d\n", major, minor);
 	DRM_DEBUG_DP("link_rate=%d\n", link_info->rate);
diff --git a/drivers/gpu/drm/msm/dp/dp_panel.h b/drivers/gpu/drm/msm/dp/dp_panel.h
index 9023e5b..1876f5e 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.h
+++ b/drivers/gpu/drm/msm/dp/dp_panel.h
@@ -51,6 +51,7 @@ struct dp_panel {
 	u32 vic;
 	u32 max_pclk_khz;
 	u32 max_dp_lanes;
+	u32 max_link_rate;
 
 	u32 max_bw_code;
 };
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.c b/drivers/gpu/drm/msm/dp/dp_parser.c
index 0519dd3..d8b6898 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.c
+++ b/drivers/gpu/drm/msm/dp/dp_parser.c
@@ -87,6 +87,8 @@ static int dp_parser_misc(struct dp_parser *parser)
 	struct device_node *of_node = parser->pdev->dev.of_node;
 	int len = 0;
 	const char *data_lane_property = "data-lanes";
+	const char *link_rate_property = "link-rate";
+	u32 rate = 0;
 
 	len = of_property_count_elems_of_size(of_node,
 			 data_lane_property, sizeof(u32));
@@ -97,6 +99,17 @@ static int dp_parser_misc(struct dp_parser *parser)
 	}
 
 	parser->max_dp_lanes = len;
+
+	len = of_property_count_elems_of_size(of_node,
+			 link_rate_property, sizeof(u32));
+
+	if (len == 1) {
+		of_property_read_u32_index(of_node,
+				link_rate_property, 0, &rate);
+
+		parser->max_link_rate = rate;
+	}
+
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/msm/dp/dp_parser.h b/drivers/gpu/drm/msm/dp/dp_parser.h
index 34b4962..7046fce 100644
--- a/drivers/gpu/drm/msm/dp/dp_parser.h
+++ b/drivers/gpu/drm/msm/dp/dp_parser.h
@@ -116,6 +116,7 @@ struct dp_parser {
 	struct dp_display_data disp_data;
 	const struct dp_regulator_cfg *regulator_cfg;
 	u32 max_dp_lanes;
+	u32 max_link_rate;
 
 	int (*parse)(struct dp_parser *parser);
 };
-- 
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