linux-kernel - [PATCH] drm/amd/display: Add dp_decide_lane

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Message-ID: <20250320032725.909-1-vulab@iscas.ac.cn>
Date: Thu, 20 Mar 2025 11:27:25 +0800
From: Wentao Liang <vulab@...as.ac.cn>
To: harry.wentland@....com,
	sunpeng.li@....com,
	Rodrigo.Siqueira@....com,
	alexander.deucher@....com,
	christian.koenig@....com,
	Xinhui.Pan@....com,
	airlied@...il.com,
	simona@...ll.ch
Cc: amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Wentao Liang <vulab@...as.ac.cn>,
	stable@...r.kernel.org
Subject: [PATCH] drm/amd/display: Add dp_decide_lane_settings() to ensure compatibility

The dp_perform_128b_132b_channel_eq_done_sequence() calls
dp_get_lane_status_and_lane_adjust() but lacks dp_decide_lane_settings().
The dp_get_lane_status_and_lane_adjust() and dp_decide_lane_settings()
functions are essential for DisplayPort link training in the Linux kernel,
with the former retrieving lane status and adjustment needs, and the
latter determining optimal lane configurations. This omission risks
compatibility issues, particularly with lower-quality cables or displays,
as the system cannot dynamically adjust to hardware limitations,
potentially leading to failed connections. Add dp_decide_lane_settings()
to enable adaptive lane configuration.

Fixes: 630168a97314 ("drm/amd/display: move dp link training logic to link_dp_training")
Cc: stable@...r.kernel.org # 6.3+
Signed-off-by: Wentao Liang <vulab@...as.ac.cn>
---
 .../amd/display/dc/link/protocols/link_dp_training_128b_132b.c  | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training_128b_132b.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training_128b_132b.c
index db87cfe37b5c..99aae3e43106 100644
--- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training_128b_132b.c
+++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training_128b_132b.c
@@ -176,6 +176,8 @@ static enum link_training_result dp_perform_128b_132b_cds_done_sequence(
 		wait_time += lt_settings->cds_pattern_time;
 		status = dp_get_lane_status_and_lane_adjust(link, lt_settings, dpcd_lane_status,
 						&dpcd_lane_status_updated, dpcd_lane_adjust, DPRX);
+		dp_decide_lane_settings(lt_settings, dpcd_lane_adjust,
+				lt_settings->hw_lane_settings, lt_settings->dpcd_lane_settings);
 		if (status != DC_OK) {
 			result = LINK_TRAINING_ABORT;
 		} else if (dp_is_symbol_locked(lt_settings->link_settings.lane_count, dpcd_lane_status) &&
-- 
2.42.0.windows.2