drm/ttm: rework pipelined eviction fence handling

Until now ttm stored a single pipelined eviction fence which means
drivers had to use a single entity for these evictions.

To lift this requirement, this commit allows up to 8 entities to
be used.

Ideally a dma_resv object would have been used as a container of
the eviction fences, but the locking rules makes it complex.
dma_resv all have the same ww_class, which means "Attempting to
lock more mutexes after ww_acquire_done." is an error.

One alternative considered was to introduced a 2nd ww_class for
specific resv to hold a single "transient" lock (= the resv lock
would only be held for a short period, without taking any other
locks).

The other option, is to statically reserve a fence array, and
extend the existing code to deal with N fences, instead of 1.

The driver is still responsible to reserve the correct number
of fence slots.

Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Link: https://lore.kernel.org/r/20251121101315.3585-20-pierre-eric.pelloux-prayer@amd.com
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>

1 files changed, 20 insertions, 13 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 1a39c30f22fb..f5aa29dc6ec0 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -524,14 +524,15 @@ void ttm_resource_manager_init(struct ttm_resource_manager *man,
 {
 	unsigned i;
 
-	spin_lock_init(&man->move_lock);
 	man->bdev = bdev;
 	man->size = size;
 	man->usage = 0;
 
 	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i)
 		INIT_LIST_HEAD(&man->lru[i]);
-	man->move = NULL;
+	spin_lock_init(&man->eviction_lock);
+	for (i = 0; i < TTM_NUM_MOVE_FENCES; i++)
+		man->eviction_fences[i] = NULL;
 }
 EXPORT_SYMBOL(ttm_resource_manager_init);
 
@@ -552,7 +553,7 @@ int ttm_resource_manager_evict_all(struct ttm_device *bdev,
 		.no_wait_gpu = false,
 	};
 	struct dma_fence *fence;
-	int ret;
+	int ret, i;
 
 	do {
 		ret = ttm_bo_evict_first(bdev, man, &ctx);
@@ -562,18 +563,24 @@ int ttm_resource_manager_evict_all(struct ttm_device *bdev,
 	if (ret && ret != -ENOENT)
 		return ret;
 
-	spin_lock(&man->move_lock);
-	fence = dma_fence_get(man->move);
-	spin_unlock(&man->move_lock);
-
-	if (fence) {
-		ret = dma_fence_wait(fence, false);
-		dma_fence_put(fence);
-		if (ret)
-			return ret;
+	ret = 0;
+
+	spin_lock(&man->eviction_lock);
+	for (i = 0; i < TTM_NUM_MOVE_FENCES; i++) {
+		fence = man->eviction_fences[i];
+		if (fence && !dma_fence_is_signaled(fence)) {
+			dma_fence_get(fence);
+			spin_unlock(&man->eviction_lock);
+			ret = dma_fence_wait(fence, false);
+			dma_fence_put(fence);
+			if (ret)
+				return ret;
+			spin_lock(&man->eviction_lock);
+		}
 	}
+	spin_unlock(&man->eviction_lock);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL(ttm_resource_manager_evict_all);