[PATCH AUTOSEL 5.6 21/47] drm/amd/display: DP training to set properly SCRAMBLING_DISABLE

Sasha Levin
2020-05-28T12:05:52Z

From: Vladimir Stempen <vladimir.stempen@amd.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@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.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