drm/amd/display: Clear lane settings after LTTPRs have been trained

[Why]
The voltage swing has to start from the minimum level when transmit TPS1 over
Main-Link in clock recovery sequence.
The lane settings from current design will inherit the existing VS/PE values
that could be adjusted by Repeater X, and to use the adjusted voltage swing level
in Repeater X-1 or DPRX could violate DP specs.

[How]
To reset VS from lane settings after LTTPRs have been trained to meet the requirement.

Signed-off-by: Martin Tsai <[e-mail]>
Reviewed-by: Wenjing Liu <[e-mail]>
Acked-by: Bindu Ramamurthy <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

···
 
 	uint8_t repeater_cnt;
 	uint8_t repeater_id;
+	uint8_t lane = 0;
 
 	if (link->ctx->dc->work_arounds.lt_early_cr_pattern)
 		start_clock_recovery_pattern_early(link, lt_settings, DPRX);
···
 
 			repeater_training_done(link, repeater_id);
 		}
+
+		for (lane = 0; lane < (uint8_t)lt_settings->link_settings.lane_count; lane++)
+			lt_settings->lane_settings[lane].VOLTAGE_SWING = VOLTAGE_SWING_LEVEL0;
 	}
 
 	if (status == LINK_TRAINING_SUCCESS) {