drm/amd/display: prefer preferred link cap over verified link settings

[why]
when preferred link cap is set, we should always use
preferred in all validation.
we should not use preferred for some validation but use
verified for others.

[how]
create getter function that gets verified link cap.
if preferred is set, return preferred link settings instead.
Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Nikola Cornij <Nikola.Cornij@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -597,6 +597,15 @@ uint32_t dc_link_bandwidth_kbps(
 
 }
 
+const struct dc_link_settings *dc_link_get_verified_link_cap(
+		const struct dc_link *link)
+{
+	if (link->preferred_link_setting.lane_count != LANE_COUNT_UNKNOWN &&
+			link->preferred_link_setting.link_rate != LINK_RATE_UNKNOWN)
+		return &link->preferred_link_setting;
+	return &link->verified_link_cap;
+}
+
 static void destruct(struct dc *dc)
 {
 	dc_release_state(dc->current_state);

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

@@ -1549,7 +1549,7 @@ bool dp_validate_mode_timing(
 		return true;
 
 	/* We always use verified link settings */
-	link_setting = &link->verified_link_cap;
+	link_setting = dc_link_get_verified_link_cap(link);
 
 	/* TODO: DYNAMIC_VALIDATION needs to be implemented */
 	/*if (flags.DYNAMIC_VALIDATION == 1 &&

drivers/gpu/drm/amd/display/dc/dc_link.h

@@ -250,6 +250,9 @@ uint32_t dc_link_bandwidth_kbps(
 	const struct dc_link *link,
 	const struct dc_link_settings *link_setting);
 
+const struct dc_link_settings *dc_link_get_verified_link_cap(
+		const struct dc_link *link);
+
 bool dc_submit_i2c(
 		struct dc *dc,
 		uint32_t link_index,