drm/amd/display: refine to decide the verified link setting

[WHY]
We return false by default when link training fail at link loss.
It will cause we get a fail verified link caps directly.

[HOW]
Record the highest verified link caps. Use the recorded value as
the verified link caps if it is not successful in the last attempt
to avoid to use the lowest link setting.

Reviewed-by: Wenjing Liu <[email protected]>
Acked-by: Alan Liu <[email protected]>
Signed-off-by: Zhikai Zhai <[email protected]>
Tested-by: Daniel Wheeler <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

1 files changed, 12 insertions, 5 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
index 3a5e80b57711..03aae0c25022 100644
--- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
+++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c
@@ -2165,7 +2165,9 @@ static bool dp_verify_link_cap(
 							link,
 							&irq_data))
 				(*fail_count)++;
-
+		} else if (status == LINK_TRAINING_LINK_LOSS) {
+			success = true;
+			(*fail_count)++;
 		} else {
 			(*fail_count)++;
 		}
@@ -2188,6 +2190,7 @@ bool dp_verify_link_cap_with_retries(
 	int i = 0;
 	bool success = false;
 	int fail_count = 0;
+	struct dc_link_settings last_verified_link_cap = fail_safe_link_settings;
 
 	dp_trace_detect_lt_init(link);
 
@@ -2204,10 +2207,14 @@ bool dp_verify_link_cap_with_retries(
 		if (!link_detect_connection_type(link, &type) || type == dc_connection_none) {
 			link->verified_link_cap = fail_safe_link_settings;
 			break;
-		} else if (dp_verify_link_cap(link, known_limit_link_setting,
-				&fail_count) && fail_count == 0) {
-			success = true;
-			break;
+		} else if (dp_verify_link_cap(link, known_limit_link_setting, &fail_count)) {
+			last_verified_link_cap = link->verified_link_cap;
+			if (fail_count == 0) {
+				success = true;
+				break;
+			}
+		} else {
+			link->verified_link_cap = last_verified_link_cap;
 		}
 		fsleep(10 * 1000);
 	}