From 6eb3cf2e06d22b2b08e6b0ab48cb9c05a8e1a107 Mon Sep 17 00:00:00 2001
From: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Date: Mon, 29 Jun 2020 13:03:52 -0400
Subject: [PATCH] drm/amd/display: Only revalidate bandwidth on medium and fast updates
Git-commit: 6eb3cf2e06d22b2b08e6b0ab48cb9c05a8e1a107
Patch-mainline: v5.8-rc4
References: git-fixes

[Why]
Changes that are fast don't require updating DLG parameters making
this call unnecessary. Considering this is an expensive call it should
not be done on every flip.

DML touches clocks, p-state support, DLG params and a few other DC
internal flags and these aren't expected during fast. A hang has been
reported with this change when called on every flip which suggests that
modifying these fields is not recommended behavior on fast updates.

[How]
Guard the validation to only happen if update type isn't FAST.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1191
Fixes: a24eaa5c51255b ("drm/amd/display: Revalidate bandwidth before commiting DC updates")
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/amd/display/dc/core/dc.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 6f93a6ca4cf0..d016f50e187c 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -2538,10 +2538,12 @@ void dc_commit_updates_for_stream(struct dc *dc,
 
 	copy_stream_update_to_stream(dc, context, stream, stream_update);
 
-	if (!dc->res_pool->funcs->validate_bandwidth(dc, context, false)) {
-		DC_ERROR("Mode validation failed for stream update!\n");
-		dc_release_state(context);
-		return;
+	if (update_type > UPDATE_TYPE_FAST) {
+		if (!dc->res_pool->funcs->validate_bandwidth(dc, context, false)) {
+			DC_ERROR("Mode validation failed for stream update!\n");
+			dc_release_state(context);
+			return;
+		}
 	}
 
 	commit_planes_for_stream(
-- 
2.16.4