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/

drivers/dma-buf/dma-fence-chain.c

@@ -193,6 +193,7 @@ static void dma_fence_chain_release(struct dma_fence *fence)
 }
 
 const struct dma_fence_ops dma_fence_chain_ops = {
+	.use_64bit_seqno = true,
 	.get_driver_name = dma_fence_chain_get_driver_name,
 	.get_timeline_name = dma_fence_chain_get_timeline_name,
 	.enable_signaling = dma_fence_chain_enable_signaling,
@@ -225,7 +226,7 @@ void dma_fence_chain_init(struct dma_fence_chain *chain,
 	init_irq_work(&chain->work, dma_fence_chain_irq_work);
 
 	/* Try to reuse the context of the previous chain node. */
-	if (prev_chain && __dma_fence_is_later(seqno, prev->seqno)) {
+	if (prev_chain && __dma_fence_is_later(seqno, prev->seqno, prev->ops)) {
 		context = prev->context;
 		chain->prev_seqno = prev->seqno;
 	} else {

drivers/dma-buf/sw_sync.c

@@ -161,7 +161,7 @@ static bool timeline_fence_signaled(struct dma_fence *fence)
 {
 	struct sync_timeline *parent = dma_fence_parent(fence);
 
-	return !__dma_fence_is_later(fence->seqno, parent->value);
+	return !__dma_fence_is_later(fence->seqno, parent->value, fence->ops);
 }
 
 static bool timeline_fence_enable_signaling(struct dma_fence *fence)

drivers/dma-buf/sync_file.c

@@ -258,7 +258,8 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
 
 			i_b++;
 		} else {
-			if (__dma_fence_is_later(pt_a->seqno, pt_b->seqno))
+			if (__dma_fence_is_later(pt_a->seqno, pt_b->seqno,
+						 pt_a->ops))
 				add_fence(fences, &i, pt_a);
 			else
 				add_fence(fences, &i, pt_b);

include/linux/dma-fence.h

@@ -111,6 +111,14 @@ 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:
 	 *
@@ -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);
 }
 
 /**