drm/amd/display: Retry when fail reading lane status during LT

[Why]
In dp_get_lane_status_and_lane_adjust(), we call core_link_read_dpcd()
to get lane status but we ignore the return value of the function. If
there is problem with AUX and we eventually can only get partial data
from monitor, we might misuse the data to jude the link training result.
Which could have us trapped in the dc_link_dp_perform_link_training()
since we thought that we can still give a try on another link setting.

[How]
In dp_get_lane_status_and_lane_adjust(), take return value of
core_link_read_dpcd() into account. If we fail to read all requested
data, we treat lanes status as previous one and repeat LT steps again.
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Agustin Gutierrez <agustin.gutierrez@amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin@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/core/dc_link_dp.c

@@ -984,6 +984,14 @@ enum dc_status dp_get_lane_status_and_lane_adjust(
 		(uint8_t *)(dpcd_buf),
 		sizeof(dpcd_buf));
 
+	if (status != DC_OK) {
+		DC_LOG_HW_LINK_TRAINING("%s:\n Failed to read from address 0x%X,"
+			" keep current lane status and lane adjust unchanged",
+			__func__,
+			lane01_status_address);
+		return status;
+	}
+
 	for (lane = 0; lane <
 		(uint32_t)(link_training_setting->link_settings.lane_count);
 		lane++) {
@@ -1124,6 +1132,9 @@ static bool perform_post_lt_adj_req_sequence(
 	uint32_t adj_req_timer;
 	bool req_drv_setting_changed;
 	uint32_t lane;
+	union lane_status dpcd_lane_status[LANE_COUNT_DP_MAX] = {0};
+	union lane_align_status_updated dpcd_lane_status_updated = {0};
+	union lane_adjust dpcd_lane_adjust[LANE_COUNT_DP_MAX] = {0};
 
 	req_drv_setting_changed = false;
 	for (adj_req_count = 0; adj_req_count < POST_LT_ADJ_REQ_LIMIT;
@@ -1135,11 +1146,6 @@ static bool perform_post_lt_adj_req_sequence(
 			adj_req_timer < POST_LT_ADJ_REQ_TIMEOUT;
 			adj_req_timer++) {
 
-			union lane_status dpcd_lane_status[LANE_COUNT_DP_MAX];
-			union lane_align_status_updated
-				dpcd_lane_status_updated;
-			union lane_adjust dpcd_lane_adjust[LANE_COUNT_DP_MAX] = { { {0} } };
-
 			dp_get_lane_status_and_lane_adjust(
 				link,
 				lt_settings,
@@ -1366,6 +1372,10 @@ static enum link_training_result perform_clock_recovery_sequence(
 	retries_cr = 0;
 	retry_count = 0;
 
+	memset(&dpcd_lane_status, '\0', sizeof(dpcd_lane_status));
+	memset(&dpcd_lane_status_updated, '\0',
+	sizeof(dpcd_lane_status_updated));
+
 	if (!link->ctx->dc->work_arounds.lt_early_cr_pattern)
 		dp_set_hw_training_pattern(link, link_res, lt_settings->pattern_for_cr, offset);
 
@@ -1377,9 +1387,6 @@ static enum link_training_result perform_clock_recovery_sequence(
 	while ((retries_cr < LINK_TRAINING_MAX_RETRY_COUNT) &&
 		(retry_count < LINK_TRAINING_MAX_CR_RETRY)) {
 
-		memset(&dpcd_lane_status, '\0', sizeof(dpcd_lane_status));
-		memset(&dpcd_lane_status_updated, '\0',
-		sizeof(dpcd_lane_status_updated));
 
 		/* 1. call HWSS to set lane settings*/
 		dp_set_hw_lane_settings(
@@ -2475,12 +2482,13 @@ static enum link_training_result dp_perform_fixed_vs_pe_training_sequence(
 		retries_cr = 0;
 		retry_count = 0;
 
+		memset(&dpcd_lane_status, '\0', sizeof(dpcd_lane_status));
+		memset(&dpcd_lane_status_updated, '\0',
+		sizeof(dpcd_lane_status_updated));
+
 		while ((retries_cr < LINK_TRAINING_MAX_RETRY_COUNT) &&
 			(retry_count < LINK_TRAINING_MAX_CR_RETRY)) {
 
-			memset(&dpcd_lane_status, '\0', sizeof(dpcd_lane_status));
-			memset(&dpcd_lane_status_updated, '\0',
-			sizeof(dpcd_lane_status_updated));
 
 			/* 1. call HWSS to set lane settings */
 			dp_set_hw_lane_settings(