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From bab52b2a79a219932a497777198c86614a467849 Mon Sep 17 00:00:00 2001
From: Samson Tam <Samson.Tam@amd.com>
Date: Tue, 4 Jun 2019 15:52:59 -0400
Subject: [PATCH 3024/4256] drm/amd/display: skip retrain in
dc_link_set_preferred_link_settings() if using passive dongle
[Why]
Fixes issue when we have a display connected using a passive
dongle and then emulate over it using a DP connection at 1 x 1.62 Ghz.
System hangs because register bus returns back 0xFFFFFFFF for all
register reads after setting register DIG_BE_CNTL in
dcn10_link_encoder_connect_dig_be_to_fe(). Hang occurs later
when trying to do a register read.
[How]
At the start of the emulation, dc_link_set_preferred_link_settings()
and dp_retrain_link_dp_test() is called, even though it is connected
using a passive dongle.
Add an extra condition in dp_retrain_link_dp_test() to check for
link->dongle_max_pix_clk > 0. This is the only way we know if the
connection is using passive dongle so we don't retrain DP.
Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
---
drivers/gpu/drm/amd/display/dc/core/dc_link.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index accd0f72e03f..551fff68a5dc 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -2998,8 +2998,10 @@ void dc_link_set_preferred_link_settings(struct dc *dc,
/* Retrain with preferred link settings only relevant for
* DP signal type
+ * Check for non-DP signal or if passive dongle present
*/
- if (!dc_is_dp_signal(link->connector_signal))
+ if (!dc_is_dp_signal(link->connector_signal) ||
+ link->dongle_max_pix_clk > 0)
return;
for (i = 0; i < MAX_PIPES; i++) {
--
2.17.1
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