[PATCH 23/30] drm/amd/display: Fix link training fallback logic

[Timo Aaltonen]

From: Jimmy Kizito <Jimmy.Kizito at amd.com>

BugLink: https://bugs.launchpad.net/bugs/1951868

[Why]
Link training should fail if stream bandwidth exceeds link bandwidth.

[How]
Correct fallback logic and use named variables to make intention clear.

Reviewed-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram at amd.com>
Reviewed-by: Jun Lei <Jun.Lei at amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito at amd.com>
Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
(cherry picked from commit 4de0bfe67bc98fb2a1115bc58ef3b9bc21717629)
Signed-off-by: Timo Aaltonen <timo.aaltonen at canonical.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index af721ded8458..350cd7e1e515 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -1891,12 +1891,16 @@ bool perform_link_training_with_retries(
 			if (type == dc_connection_none)
 				break;
 		} else if (do_fallback) {
+			uint32_t req_bw;
+			uint32_t link_bw;
+
 			decide_fallback_link_setting(*link_setting, &current_setting, status);
 			/* Fail link training if reduced link bandwidth no longer meets
 			 * stream requirements.
 			 */
-			if (dc_bandwidth_in_kbps_from_timing(&stream->timing) <
-					dc_link_bandwidth_kbps(link, &current_setting))
+			req_bw = dc_bandwidth_in_kbps_from_timing(&stream->timing);
+			link_bw = dc_link_bandwidth_kbps(link, &current_setting);
+			if (req_bw > link_bw)
 				break;
 		}
 
-- 
2.32.0