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, 6 insertions, 5 deletions

diff --git a/drivers/gpu/drm/ttm/tests/ttm_bo_validate_test.c b/drivers/gpu/drm/ttm/tests/ttm_bo_validate_test.c
index 17a570af296c..2eda87882e65 100644
--- a/drivers/gpu/drm/ttm/tests/ttm_bo_validate_test.c
+++ b/drivers/gpu/drm/ttm/tests/ttm_bo_validate_test.c
@@ -652,7 +652,7 @@ static void ttm_bo_validate_move_fence_signaled(struct kunit *test)
 	int err;
 
 	man = ttm_manager_type(priv->ttm_dev, mem_type);
-	man->move = dma_fence_get_stub();
+	man->eviction_fences[0] = dma_fence_get_stub();
 
 	bo = ttm_bo_kunit_init(test, test->priv, size, NULL);
 	bo->type = bo_type;
@@ -669,7 +669,7 @@ static void ttm_bo_validate_move_fence_signaled(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, ctx.bytes_moved, size);
 
 	ttm_bo_fini(bo);
-	dma_fence_put(man->move);
+	dma_fence_put(man->eviction_fences[0]);
 }
 
 static const struct ttm_bo_validate_test_case ttm_bo_validate_wait_cases[] = {
@@ -733,9 +733,9 @@ static void ttm_bo_validate_move_fence_not_signaled(struct kunit *test)
 
 	spin_lock_init(&fence_lock);
 	man = ttm_manager_type(priv->ttm_dev, fst_mem);
-	man->move = alloc_mock_fence(test);
+	man->eviction_fences[0] = alloc_mock_fence(test);
 
-	task = kthread_create(threaded_fence_signal, man->move, "move-fence-signal");
+	task = kthread_create(threaded_fence_signal, man->eviction_fences[0], "move-fence-signal");
 	if (IS_ERR(task))
 		KUNIT_FAIL(test, "Couldn't create move fence signal task\n");
 
@@ -743,7 +743,8 @@ static void ttm_bo_validate_move_fence_not_signaled(struct kunit *test)
 	err = ttm_bo_validate(bo, placement_val, &ctx_val);
 	dma_resv_unlock(bo->base.resv);
 
-	dma_fence_wait_timeout(man->move, false, MAX_SCHEDULE_TIMEOUT);
+	dma_fence_wait_timeout(man->eviction_fences[0], false, MAX_SCHEDULE_TIMEOUT);
+	man->eviction_fences[0] = NULL;
 
 	KUNIT_EXPECT_EQ(test, err, 0);
 	KUNIT_EXPECT_EQ(test, ctx_val.bytes_moved, size);