[PATCH 05/15] drm/amd/display: do not calculate DP2.0 SST payload when link is off

[Stylon Wang]

From: Wenjing Liu <wenjing.liu at amd.com>

[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 at amd.com>
Acked-by: Stylon Wang <stylon.wang at amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu at amd.com>
---
 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);
-- 
2.35.1