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, 3 insertions, 2 deletions

diff --git a/drivers/gpu/drm/ttm/tests/ttm_resource_test.c b/drivers/gpu/drm/ttm/tests/ttm_resource_test.c
index e6ea2bd01f07..c0e4e35e0442 100644
--- a/drivers/gpu/drm/ttm/tests/ttm_resource_test.c
+++ b/drivers/gpu/drm/ttm/tests/ttm_resource_test.c
@@ -207,6 +207,7 @@ static void ttm_resource_manager_init_basic(struct kunit *test)
 	struct ttm_resource_test_priv *priv = test->priv;
 	struct ttm_resource_manager *man;
 	size_t size = SZ_16K;
+	int i;
 
 	man = kunit_kzalloc(test, sizeof(*man), GFP_KERNEL);
 	KUNIT_ASSERT_NOT_NULL(test, man);
@@ -216,8 +217,8 @@ static void ttm_resource_manager_init_basic(struct kunit *test)
 	KUNIT_ASSERT_PTR_EQ(test, man->bdev, priv->devs->ttm_dev);
 	KUNIT_ASSERT_EQ(test, man->size, size);
 	KUNIT_ASSERT_EQ(test, man->usage, 0);
-	KUNIT_ASSERT_NULL(test, man->move);
-	KUNIT_ASSERT_NOT_NULL(test, &man->move_lock);
+	for (i = 0; i < TTM_NUM_MOVE_FENCES; i++)
+		KUNIT_ASSERT_NULL(test, man->eviction_fences[i]);
 
 	for (int i = 0; i < TTM_MAX_BO_PRIORITY; ++i)
 		KUNIT_ASSERT_TRUE(test, list_empty(&man->lru[i]));