From c720b26027c000d9667df2c7ffeecca3dcc744a5 Mon Sep 17 00:00:00 2001
From: Wenjing Liu <wenjing.liu@amd.com>
Date: Fri, 29 Apr 2022 15:42:30 -0400
Subject: drm/amd/display: do not calculate DP2.0 SST payload when link is off
Git-commit: c371b0d12d0b8497355cc1ac2a11accd2f5b8528
Patch-mainline: v5.19-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

[Why & How]
There is a chance where the RX issues HPD deassert in the
middle of link training, this will cause our logic to
abort link training and turn off link. However our payload
allocation logic needs to use current link settings to
determine average time slot per MTP. This will need to
use current link bandwidth as divider. This causes divide
by zero error occasionally. The fix is to skip DP2.0 payload
allocation logic if current link is not in 128b/132b mode.

Reviewed-by: George Shen <George.Shen@amd.com>
Acked-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index 48e274f9ea84..07f154fc4e56 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -3546,7 +3546,8 @@ static enum dc_status dc_link_update_sst_payload(struct pipe_ctx *pipe_ctx,
 	}
 
 	/* slot X.Y for SST payload allocate */
-	if (allocate) {
+	if (allocate && dp_get_link_encoding_format(&link->cur_link_settings) ==
+			DP_128b_132b_ENCODING) {
 		avg_time_slots_per_mtp = calculate_sst_avg_time_slots_per_mtp(stream, link);
 
 		dc_log_vcp_x_y(link, avg_time_slots_per_mtp);
-- 
2.38.1