linux-kernel - [PATCH AUTOSEL 6.6 01/20] drm/amd/display: Add delay to improve LTTPR UHBR interop

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Message-ID: <20240728154605.2048490-1-sashal@kernel.org>
Date: Sun, 28 Jul 2024 11:44:59 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Michael Strauss <michael.strauss@....com>,
	Wenjing Liu <wenjing.liu@....com>,
	Aurabindo Pillai <aurabindo.pillai@....com>,
	Daniel Wheeler <daniel.wheeler@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>,
	harry.wentland@....com,
	sunpeng.li@....com,
	Rodrigo.Siqueira@....com,
	christian.koenig@....com,
	Xinhui.Pan@....com,
	airlied@...il.com,
	daniel@...ll.ch,
	stylon.wang@....com,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.6 01/20] drm/amd/display: Add delay to improve LTTPR UHBR interop

From: Michael Strauss <michael.strauss@....com>

[ Upstream commit 10839ee6a977ed1f7d0f4deb29f2d7e5d1f2a9dd ]

[WHY]
Avoid race condition which puts LTTPR into bad state during UHBR LT.

[HOW]
Delay 30ms between starting UHBR TPS1 PHY output and sending TPS1 via DPCD.

Reviewed-by: Wenjing Liu <wenjing.liu@....com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@....com>
Signed-off-by: Michael Strauss <michael.strauss@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../dc/link/hwss/link_hwss_hpo_fixed_vs_pe_retimer_dp.c      | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_hpo_fixed_vs_pe_retimer_dp.c b/drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_hpo_fixed_vs_pe_retimer_dp.c
index b621b97711b61..a7f5b0f6272ce 100644
--- a/drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_hpo_fixed_vs_pe_retimer_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_hpo_fixed_vs_pe_retimer_dp.c
@@ -162,7 +162,12 @@ static void set_hpo_fixed_vs_pe_retimer_dp_link_test_pattern(struct dc_link *lin
 		link_res->hpo_dp_link_enc->funcs->set_link_test_pattern(
 				link_res->hpo_dp_link_enc, tp_params);
 	}
+
 	link->dc->link_srv->dp_trace_source_sequence(link, DPCD_SOURCE_SEQ_AFTER_SET_SOURCE_PATTERN);
+
+	// Give retimer extra time to lock before updating DP_TRAINING_PATTERN_SET to TPS1
+	if (tp_params->dp_phy_pattern == DP_TEST_PATTERN_128b_132b_TPS1_TRAINING_MODE)
+		msleep(30);
 }
 
 static void set_hpo_fixed_vs_pe_retimer_dp_lane_settings(struct dc_link *link,
-- 
2.43.0