linux-kernel - [PATCH v3 3/4] drm/msm/dp: Prepare for link training per-segment for LTTPRs

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Message-ID: <20250417021349.148911-4-alex.vinarskis@gmail.com>
Date: Thu, 17 Apr 2025 04:10:34 +0200
From: Aleksandrs Vinarskis <alex.vinarskis@...il.com>
To: Dmitry Baryshkov <lumag@...nel.org>,
	linux-arm-msm@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	freedreno@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	dmitry.baryshkov@....qualcomm.com
Cc: Rob Clark <robdclark@...il.com>,
	Abhinav Kumar <quic_abhinavk@...cinc.com>,
	Sean Paul <sean@...rly.run>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	laurentiu.tudor1@...l.com,
	abel.vesa@...aro.org,
	johan@...nel.org,
	Aleksandrs Vinarskis <alex.vinarskis@...il.com>
Subject: [PATCH v3 3/4] drm/msm/dp: Prepare for link training per-segment for LTTPRs

Per-segment link training requires knowing the number of LTTPRs
(if any) present. Store the count during LTTPRs' initialization.

Signed-off-by: Aleksandrs Vinarskis <alex.vinarskis@...il.com>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 17 +++++++++++------
 drivers/gpu/drm/msm/dp/dp_link.h    |  1 +
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index 5c57c1d7ac60..ab8c1f19dcb4 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -367,16 +367,21 @@ static int msm_dp_display_send_hpd_notification(struct msm_dp_display_private *d
 	return 0;
 }
 
-static void msm_dp_display_lttpr_init(struct msm_dp_display_private *dp, u8 *dpcd)
+static int msm_dp_display_lttpr_init(struct msm_dp_display_private *dp, u8 *dpcd)
 {
-	int rc;
+	int rc, lttpr_count;
 
 	if (drm_dp_read_lttpr_common_caps(dp->aux, dpcd, dp->link->lttpr_common_caps))
-		return;
+		return 0;
 
-	rc = drm_dp_lttpr_init(dp->aux, drm_dp_lttpr_count(dp->link->lttpr_common_caps));
-	if (rc)
+	lttpr_count = drm_dp_lttpr_count(dp->link->lttpr_common_caps);
+	rc = drm_dp_lttpr_init(dp->aux, lttpr_count);
+	if (rc) {
 		DRM_ERROR("failed to set LTTPRs transparency mode, rc=%d\n", rc);
+		return 0;
+	}
+
+	return lttpr_count;
 }
 
 static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
@@ -390,7 +395,7 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
 	if (rc)
 		goto end;
 
-	msm_dp_display_lttpr_init(dp, dpcd);
+	dp->link->lttpr_count = msm_dp_display_lttpr_init(dp, dpcd);
 
 	rc = msm_dp_panel_read_sink_caps(dp->panel, connector);
 	if (rc)
diff --git a/drivers/gpu/drm/msm/dp/dp_link.h b/drivers/gpu/drm/msm/dp/dp_link.h
index c47d75cfc720..ba47c6d19fbf 100644
--- a/drivers/gpu/drm/msm/dp/dp_link.h
+++ b/drivers/gpu/drm/msm/dp/dp_link.h
@@ -62,6 +62,7 @@ struct msm_dp_link_phy_params {
 
 struct msm_dp_link {
 	u8 lttpr_common_caps[DP_LTTPR_COMMON_CAP_SIZE];
+	int lttpr_count;
 
 	u32 sink_request;
 	u32 test_response;
-- 
2.45.2