dma-buf: make fence sequence numbers 64 bit v2

For a lot of use cases we need 64bit sequence numbers. Currently drivers
overload the dma_fence structure to store the additional bits.

Stop doing that and make the sequence number in the dma_fence always
64bit.

For compatibility with hardware which can do only 32bit sequences the
comparisons in __dma_fence_is_later only takes the lower 32bits as significant
when the upper 32bits are all zero.

v2: change the logic in __dma_fence_is_later

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Link: https://patchwork.freedesktop.org/patch/266927/

1 files changed, 15 insertions, 7 deletions

diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 999e4b104410..6b788467b2e3 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -77,7 +77,7 @@ struct dma_fence {
 	struct list_head cb_list;
 	spinlock_t *lock;
 	u64 context;
-	unsigned seqno;
+	u64 seqno;
 	unsigned long flags;
 	ktime_t timestamp;
 	int error;
@@ -244,7 +244,7 @@ struct dma_fence_ops {
 };
 
 void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
-		    spinlock_t *lock, u64 context, unsigned seqno);
+		    spinlock_t *lock, u64 context, u64 seqno);
 
 void dma_fence_release(struct kref *kref);
 void dma_fence_free(struct dma_fence *fence);
@@ -414,9 +414,17 @@ dma_fence_is_signaled(struct dma_fence *fence)
  * 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(u32 f1, u32 f2)
+static inline bool __dma_fence_is_later(u64 f1, u64 f2)
 {
-	return (int)(f1 - f2) > 0;
+	/* 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.
+	 */
+	if (upper_32_bits(f1) || upper_32_bits(f2))
+		return f1 > f2;
+
+	return (int)(lower_32_bits(f1) - lower_32_bits(f2)) > 0;
 }
 
 /**
@@ -548,21 +556,21 @@ u64 dma_fence_context_alloc(unsigned num);
 	do {								\
 		struct dma_fence *__ff = (f);				\
 		if (IS_ENABLED(CONFIG_DMA_FENCE_TRACE))			\
-			pr_info("f %llu#%u: " fmt,			\
+			pr_info("f %llu#%llu: " fmt,			\
 				__ff->context, __ff->seqno, ##args);	\
 	} while (0)
 
 #define DMA_FENCE_WARN(f, fmt, args...) \
 	do {								\
 		struct dma_fence *__ff = (f);				\
-		pr_warn("f %llu#%u: " fmt, __ff->context, __ff->seqno,	\
+		pr_warn("f %llu#%llu: " fmt, __ff->context, __ff->seqno,\
 			 ##args);					\
 	} while (0)
 
 #define DMA_FENCE_ERR(f, fmt, args...) \
 	do {								\
 		struct dma_fence *__ff = (f);				\
-		pr_err("f %llu#%u: " fmt, __ff->context, __ff->seqno,	\
+		pr_err("f %llu#%llu: " fmt, __ff->context, __ff->seqno,	\
 			##args);					\
 	} while (0)