drm/amd/display: Add delay to improve LTTPR UHBR interop

[WHY]
Avoid race condition which puts LTTPR into bad state during UHBR LT.

[HOW]
Delay 30ms between starting UHBR TPS1 PHY output and sending TPS1 via DPCD.
Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Michael Strauss <michael.strauss@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/link/hwss/link_hwss_hpo_fixed_vs_pe_retimer_dp.c

@@ -165,7 +165,12 @@ static void set_hpo_fixed_vs_pe_retimer_dp_link_test_pattern(struct dc_link *lin
 		link_res->hpo_dp_link_enc->funcs->set_link_test_pattern(
 				link_res->hpo_dp_link_enc, tp_params);
 	}
+
 	link->dc->link_srv->dp_trace_source_sequence(link, DPCD_SOURCE_SEQ_AFTER_SET_SOURCE_PATTERN);
+
+	// Give retimer extra time to lock before updating DP_TRAINING_PATTERN_SET to TPS1
+	if (tp_params->dp_phy_pattern == DP_TEST_PATTERN_128b_132b_TPS1_TRAINING_MODE)
+		msleep(30);
 }
 
 static void set_hpo_fixed_vs_pe_retimer_dp_lane_settings(struct dc_link *link,