[PATCH 5.19 33/48] drm/amd/display: Fix DP MST timeslot issue when fallback happened

Greg Kroah-Hartman
2022-10-10T07:14:18Z

From: Cruise Hung <Cruise.Hung@amd.com>

[ Upstream commit 20c6168b3c8aadef7d2853c925d99eb546bd5e1c ]

[Why]
When USB4 DP link training failed and fell back to lower link rate,
the time slot calculation uses the verified_link_cap.
And the verified_link_cap was not updated to the new one.
It caused the wrong VC payload time-slot was allocated.

[How]
Updated verified_link_cap with the new one from cur_link_settings
after the LT completes successfully.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Cruise Hung <Cruise.Hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

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 0c52506b367d..b4203a812c4b 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
@@ -2857,8 +2857,14 @@ bool perform_link_training_with_retries(
skip_video_pattern);

/* Transmit idle pattern once training successful. */
- if (status == LINK_TRAINING_SUCCESS && !is_link_bw_low)
+ if (status == LINK_TRAINING_SUCCESS && !is_link_bw_low) {
dp_set_hw_test_pattern(link, &pipe_ctx->link_res, DP_TEST_PATTERN_VIDEO_MODE, NULL, 0);
+ /* Update verified link settings to current one
+ * Because DPIA LT might fallback to lower link setting.
+ */
+ link->verified_link_cap.link_rate = link->cur_link_settings.link_rate;
+ link->verified_link_cap.lane_count = link->cur_link_settings.lane_count;
+ }
} else {
status = dc_link_dp_perform_link_training(link,
&pipe_ctx->link_res,
--
2.35.1