linux-kernel - [PATCH] drm/msm/dp: add support of tps4 (training pattern 4) for HBR3

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Date:   Tue, 28 Dec 2021 10:51:29 -0800
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     <robdclark@...il.com>, <sean@...rly.run>, <swboyd@...omium.org>,
        <vkoul@...nel.org>, <daniel@...ll.ch>, <airlied@...ux.ie>,
        <agross@...nel.org>, <dmitry.baryshkov@...aro.org>,
        <bjorn.andersson@...aro.org>
CC:     <quic_abhinavk@...cinc.com>, <aravindh@...eaurora.org>,
        <quic_khsieh@...cinc.com>, <quic_sbillaka@...cinc.com>,
        <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Kuogee Hsieh <khsieh@...eaurora.org>
Subject: [PATCH] drm/msm/dp: add support of tps4 (training pattern 4) for HBR3

From: Kuogee Hsieh <khsieh@...eaurora.org>

Some DP sinkers prefer to use tps4 instead of tps3 during training #2.
This patch will use tps4 to perform link training #2 if sinker's DPCD
supports it.

Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
---
 drivers/gpu/drm/msm/dp/dp_ctrl.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index 39558a2..c7b0657 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -1181,7 +1181,7 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
 			int *training_step)
 {
 	int tries = 0, ret = 0;
-	char pattern;
+	char pattern, state_ctrl_bit;
 	int const maximum_retries = 5;
 	u8 link_status[DP_LINK_STATUS_SIZE];
 
@@ -1189,12 +1189,20 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
 
 	*training_step = DP_TRAINING_2;
 
-	if (drm_dp_tps3_supported(ctrl->panel->dpcd))
+	if (drm_dp_tps4_supported(ctrl->panel->dpcd)) {
+		pattern = DP_TRAINING_PATTERN_4;
+		state_ctrl_bit = 4;
+	}
+	else if (drm_dp_tps3_supported(ctrl->panel->dpcd)) {
 		pattern = DP_TRAINING_PATTERN_3;
-	else
+		state_ctrl_bit = 3;
+	}
+	else {
 		pattern = DP_TRAINING_PATTERN_2;
+		state_ctrl_bit = 2;
+	}
 
-	ret = dp_catalog_ctrl_set_pattern(ctrl->catalog, pattern);
+	ret = dp_catalog_ctrl_set_pattern(ctrl->catalog, state_ctrl_bit);
 	if (ret)
 		return ret;
 
-- 
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