linux-kernel - [PATCH AUTOSEL 6.12 158/486] drm/amd/display: not abort link train when bw is low

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Message-Id: <20250505223922.2682012-158-sashal@kernel.org>
Date: Mon,  5 May 2025 18:33:54 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Peichen Huang <PeiChen.Huang@....com>,
	Cruise Hung <cruise.hung@....com>,
	Meenakshikumar Somasundaram <meenakshikumar.somasundaram@....com>,
	Tom Chung <chiahsuan.chung@....com>,
	Daniel Wheeler <daniel.wheeler@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>,
	harry.wentland@....com,
	sunpeng.li@....com,
	christian.koenig@....com,
	airlied@...il.com,
	simona@...ll.ch,
	wenjing.liu@....com,
	alex.hung@....com,
	Jerry.Zuo@....com,
	michael.strauss@....com,
	Brendan.Tam@....com,
	ivlipski@....com,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.12 158/486] drm/amd/display: not abort link train when bw is low

From: Peichen Huang <PeiChen.Huang@....com>

[ Upstream commit 8a21da2842bb22b2b80e5902d0438030d729bfd3 ]

[WHY]
DP tunneling should not abort link train even bandwidth become
too low after downgrade. Otherwise, it would fail compliance test.

[HOW}
Do link train with downgrade settings even bandwidth is not enough

Reviewed-by: Cruise Hung <cruise.hung@....com>
Reviewed-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@....com>
Signed-off-by: Peichen Huang <PeiChen.Huang@....com>
Signed-off-by: Tom Chung <chiahsuan.chung@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../gpu/drm/amd/display/dc/link/protocols/link_dp_training.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c
index 27b881f947e8b..9385a32a471b8 100644
--- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c
+++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_training.c
@@ -1769,13 +1769,10 @@ bool perform_link_training_with_retries(
 			is_link_bw_min = ((cur_link_settings.link_rate <= LINK_RATE_LOW) &&
 				(cur_link_settings.lane_count <= LANE_COUNT_ONE));
 
-			if (is_link_bw_low) {
+			if (is_link_bw_low)
 				DC_LOG_WARNING(
 					"%s: Link(%d) bandwidth too low after fallback req_bw(%d) > link_bw(%d)\n",
 					__func__, link->link_index, req_bw, link_bw);
-
-				return false;
-			}
 		}
 
 		msleep(delay_between_attempts);
-- 
2.39.5