linux-kernel - [PATCH 5.6 21/43] drm/amd/display: DP training to set properly SCRAMBLING

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Date:   Fri,  5 Jun 2020 16:14:51 +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,
        Vladimir Stempen <vladimir.stempen@....com>,
        Wenjing Liu <Wenjing.Liu@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.6 21/43] drm/amd/display: DP training to set properly SCRAMBLING_DISABLE

From: Vladimir Stempen <vladimir.stempen@....com>

[ Upstream commit b6ef55ccba7ed00fc10e3e6f619c8f886162427f ]

[Why]
DP training sequence to set SCRAMBLING_DISABLE bit properly based on
training pattern - per DP Spec.

[How]
Update dpcd_pattern.v1_4.SCRAMBLING_DISABLE with 1 for TPS1, TPS2, TPS3,
but not for TPS4.

Signed-off-by: Vladimir Stempen <vladimir.stempen@....com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@....com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../gpu/drm/amd/display/dc/core/dc_link_dp.c  | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 1b6c75a4dd60..fbcd979438e2 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -220,6 +220,30 @@ static enum dpcd_training_patterns
 	return dpcd_tr_pattern;
 }
 
+static uint8_t dc_dp_initialize_scrambling_data_symbols(
+	struct dc_link *link,
+	enum dc_dp_training_pattern pattern)
+{
+	uint8_t disable_scrabled_data_symbols = 0;
+
+	switch (pattern) {
+	case DP_TRAINING_PATTERN_SEQUENCE_1:
+	case DP_TRAINING_PATTERN_SEQUENCE_2:
+	case DP_TRAINING_PATTERN_SEQUENCE_3:
+		disable_scrabled_data_symbols = 1;
+		break;
+	case DP_TRAINING_PATTERN_SEQUENCE_4:
+		disable_scrabled_data_symbols = 0;
+		break;
+	default:
+		ASSERT(0);
+		DC_LOG_HW_LINK_TRAINING("%s: Invalid HW Training pattern: %d\n",
+			__func__, pattern);
+		break;
+	}
+	return disable_scrabled_data_symbols;
+}
+
 static inline bool is_repeater(struct dc_link *link, uint32_t offset)
 {
 	return (!link->is_lttpr_mode_transparent && offset != 0);
@@ -252,6 +276,9 @@ static void dpcd_set_lt_pattern_and_lane_settings(
 	dpcd_pattern.v1_4.TRAINING_PATTERN_SET =
 		dc_dp_training_pattern_to_dpcd_training_pattern(link, pattern);
 
+	dpcd_pattern.v1_4.SCRAMBLING_DISABLE =
+		dc_dp_initialize_scrambling_data_symbols(link, pattern);
+
 	dpcd_lt_buffer[DP_TRAINING_PATTERN_SET - DP_TRAINING_PATTERN_SET]
 		= dpcd_pattern.raw;
 
-- 
2.25.1