[PATCH] drm/amd/display: Only revalidate bandwidth on medium and fast updates

[Li, Roman]

[AMD Public Use]

Reviewed-by: Roman Li <Roman.Li at amd.com>

-----Original Message-----
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of Nicholas Kazlauskas
Sent: Monday, June 29, 2020 4:49 PM
To: amd-gfx at lists.freedesktop.org
Cc: Lakha, Bhawanpreet <Bhawanpreet.Lakha at amd.com>; Siqueira, Rodrigo <Rodrigo.Siqueira at amd.com>; Wu, Hersen <hersenxs.wu at amd.com>; Kazlauskas, Nicholas <Nicholas.Kazlauskas at amd.com>
Subject: [PATCH] drm/amd/display: Only revalidate bandwidth on medium and fast updates

[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://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.freedesktop.org%2Fdrm%2Famd%2F-%2Fissues%2F1191&data=02%7C01%7Croman.li%40amd.com%7Cc98c2d3c363643a4fef208d81c6dfa68%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637290606647861029&sdata=%2B3rZlvLgef1c2FOYTKx37U%2Fbr%2BWOxI9GXVI2K7HjH3E%3D&reserved=0
Fixes: e1995f0909e3 ("drm/amd/display: Revalidate bandwidth before commiting DC updates")
Cc: Hersen Wu <hersenxs.wu at amd.com>
Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha at amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
---
 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 67402d75e67e..942ceb0f6383 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -2607,10 +2607,12 @@ 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(
--
2.25.1

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