drm/amd/display: check hpd before retry verify link cap

[why]
During detection link training if a display is disconnected,
the current code will retry 3 times of link training
on disconnected link before giving up.

[how]
Before each retry check for HPD status, only retry
verify link cap when HPD is still high.
Also put a 10ms delay between each retry to improve
the chance of success.
Signed-off-by: NWenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: NJun Lei <Jun.Lei@amd.com>
Acked-by: NAbdoulaye Berthe <Abdoulaye.Berthe@amd.com>
Acked-by: NLeo Li <sunpeng.li@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -854,16 +854,9 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
 					dc_sink_release(prev_sink);
 				} else {
 					/* Empty dongle plug in */
-					for (i = 0; i < LINK_TRAINING_MAX_VERIFY_RETRY; i++) {
-						int fail_count = 0;
-
-						dp_verify_link_cap(link,
-								  &link->reported_link_cap,
-								  &fail_count);
-
-						if (fail_count == 0)
-							break;
-					}
+					dp_verify_link_cap_with_retries(link,
+							&link->reported_link_cap,
+							LINK_TRAINING_MAX_VERIFY_RETRY);
 				}
 				return true;
 			}
@@ -967,17 +960,9 @@ bool dc_link_detect(struct dc_link *link, enum dc_detect_reason reason)
 			 */
 
 			/* deal with non-mst cases */
-			for (i = 0; i < LINK_TRAINING_MAX_VERIFY_RETRY; i++) {
-				int fail_count = 0;
-
-				dp_verify_link_cap(link,
-						  &link->reported_link_cap,
-						  &fail_count);
-
-				if (fail_count == 0)
-					break;
-			}
-
+			dp_verify_link_cap_with_retries(link,
+					&link->reported_link_cap,
+					LINK_TRAINING_MAX_VERIFY_RETRY);
 		} else {
 			// If edid is the same, then discard new sink and revert back to original sink
 			if (same_edid) {

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

@@ -1643,6 +1643,33 @@ bool dp_verify_link_cap(
 	return success;
 }
 
+bool dp_verify_link_cap_with_retries(
+	struct dc_link *link,
+	struct dc_link_settings *known_limit_link_setting,
+	int attempts)
+{
+	uint8_t i = 0;
+	bool success = false;
+
+	for (i = 0; i < attempts; i++) {
+		int fail_count = 0;
+		enum dc_connection_type type;
+
+		memset(&link->verified_link_cap, 0,
+				sizeof(struct dc_link_settings));
+		if (!dc_link_detect_sink(link, &type)) {
+			break;
+		} else if (dp_verify_link_cap(link,
+				&link->reported_link_cap,
+				&fail_count) && fail_count == 0) {
+			success = true;
+			break;
+		}
+		msleep(10);
+	}
+	return success;
+}
+
 static struct dc_link_settings get_common_supported_link_settings(
 		struct dc_link_settings link_setting_a,
 		struct dc_link_settings link_setting_b)

drivers/gpu/drm/amd/display/dc/inc/dc_link_dp.h

@@ -38,6 +38,11 @@ bool dp_verify_link_cap(
 	struct dc_link_settings *known_limit_link_setting,
 	int *fail_count);
 
+bool dp_verify_link_cap_with_retries(
+	struct dc_link *link,
+	struct dc_link_settings *known_limit_link_setting,
+	int attempts);
+
 bool dp_validate_mode_timing(
 	struct dc_link *link,
 	const struct dc_crtc_timing *timing);