dma-buf: explicitely note that dma-fence-chains use 64bit seqno

Instead of checking the upper values of the sequence number use an explicit
field in the dma_fence_ops structure to note if a sequence should be 32bit
or 64bit.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/299655/

1 files changed, 15 insertions, 6 deletions

diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 6b788467b2e3..974717d6ac0c 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -112,6 +112,14 @@ struct dma_fence_cb {
  */
 struct dma_fence_ops {
 	/**
+	 * @use_64bit_seqno:
+	 *
+	 * True if this dma_fence implementation uses 64bit seqno, false
+	 * otherwise.
+	 */
+	bool use_64bit_seqno;
+
+	/**
 	 * @get_driver_name:
 	 *
 	 * Returns the driver name. This is a callback to allow drivers to
@@ -410,18 +418,19 @@ dma_fence_is_signaled(struct dma_fence *fence)
  * __dma_fence_is_later - return if f1 is chronologically later than f2
  * @f1: the first fence's seqno
  * @f2: the second fence's seqno from the same context
+ * @ops: dma_fence_ops associated with the seqno
  *
  * Returns true if f1 is chronologically later than f2. Both fences must be
  * from the same context, since a seqno is not common across contexts.
  */
-static inline bool __dma_fence_is_later(u64 f1, u64 f2)
+static inline bool __dma_fence_is_later(u64 f1, u64 f2,
+					const struct dma_fence_ops *ops)
 {
 	/* This is for backward compatibility with drivers which can only handle
-	 * 32bit sequence numbers. Use a 64bit compare when any of the higher
-	 * bits are none zero, otherwise use a 32bit compare with wrap around
-	 * handling.
+	 * 32bit sequence numbers. Use a 64bit compare when the driver says to
+	 * do so.
 	 */
-	if (upper_32_bits(f1) || upper_32_bits(f2))
+	if (ops->use_64bit_seqno)
 		return f1 > f2;
 
 	return (int)(lower_32_bits(f1) - lower_32_bits(f2)) > 0;
@@ -441,7 +450,7 @@ static inline bool dma_fence_is_later(struct dma_fence *f1,
 	if (WARN_ON(f1->context != f2->context))
 		return false;
 
-	return __dma_fence_is_later(f1->seqno, f2->seqno);
+	return __dma_fence_is_later(f1->seqno, f2->seqno, f1->ops);
 }
 
 /**