linux-kernel - [PATCH 5.16 0517/1017] drm/msm/dp: stop link training after link training 2 failed

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Date:   Tue,  5 Apr 2022 09:23:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 0517/1017] drm/msm/dp: stop link training after link training 2 failed

From: Kuogee Hsieh <quic_khsieh@...cinc.com>

[ Upstream commit 9051d629dbf7a998a40f7eac65a9512b01bc3bb8 ]

Each DP link training contains link training 1 followed by link
training 2.  There is maximum of 5 retries of DP link training
before declared link training failed. It is required to stop link
training at end of link training 2 if it is failed so that next
link training 1 can start freshly. This patch fixes link compliance
test  case 4.3.1.13 (Source Device Link Training EQ Fallback Test).

Changes in v10:
--  group into one series

Changes in v11:
-- drop drm/msm/dp: dp_link_parse_sink_count() return immediately if aux read

Fixes: 2e0adc765d88 ("drm/msm/dp: do not end dp link training until video is ready")
Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
Reviewed-by: Stephen Boyd <swboyd@...omium.org>
Link: https://lore.kernel.org/r/1642531648-8448-5-git-send-email-quic_khsieh@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/msm/dp/dp_ctrl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index 62e75dc8afc6..4af281d97493 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -1744,6 +1744,9 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
 				/* end with failure */
 				break; /* lane == 1 already */
 			}
+
+			/* stop link training before start re training  */
+			dp_ctrl_clear_training_pattern(ctrl);
 		}
 	}
 
-- 
2.34.1