linux-kernel - [PATCH 5.7 104/112] drm/amd/display: Only revalidate bandwidth on medium and fast updates

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Date:   Tue,  7 Jul 2020 17:17:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Roman Li <Roman.Li@....com>
Subject: [PATCH 5.7 104/112] drm/amd/display: Only revalidate bandwidth on medium and fast updates

From: Nicholas Kazlauskas <nicholas.kazlauskas@....com>

commit 6eb3cf2e06d22b2b08e6b0ab48cb9c05a8e1a107 upstream.

[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@....com>
Acked-by: Alex Deucher <alexander.deucher@....com>
Reviewed-by: Roman Li <Roman.Li@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -2533,10 +2533,12 @@ void dc_commit_updates_for_stream(struct
 
 	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(