linux-kernel - [PATCH] nouveau: explicitly wait on the fence in nouveau_bo_move

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Message-Id: <20220819200928.401416-1-kherbst@redhat.com>
Date:   Fri, 19 Aug 2022 22:09:28 +0200
From:   Karol Herbst <kherbst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Ben Skeggs <bskeggs@...hat.com>, Lyude Paul <lyude@...hat.com>,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        Karol Herbst <kherbst@...hat.com>, stable@...r.kernel.org
Subject: [PATCH] nouveau: explicitly wait on the fence in nouveau_bo_move_m2mf

It is a bit unlcear to us why that's helping, but it does and unbreaks
suspend/resume on a lot of GPUs without any known drawbacks.

Cc: stable@...r.kernel.org # v5.15+
Closes: https://gitlab.freedesktop.org/drm/nouveau/-/issues/156
Signed-off-by: Karol Herbst <kherbst@...hat.com>
---
 drivers/gpu/drm/nouveau/nouveau_bo.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 35bb0bb3fe61..126b3c6e12f9 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -822,6 +822,15 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict,
 		if (ret == 0) {
 			ret = nouveau_fence_new(chan, false, &fence);
 			if (ret == 0) {
+				/* TODO: figure out a better solution here
+				 *
+				 * wait on the fence here explicitly as going through
+				 * ttm_bo_move_accel_cleanup somehow doesn't seem to do it.
+				 *
+				 * Without this the operation can timeout and we'll fallback to a
+				 * software copy, which might take several minutes to finish.
+				 */
+				nouveau_fence_wait(fence, false, false);
 				ret = ttm_bo_move_accel_cleanup(bo,
 								&fence->base,
 								evict, false,
-- 
2.37.1