dma-buf: cleanup dma_fence_describe v3

The driver and timeline name are meaningless for signaled fences.

Drop them and also print the context number.

v2: avoid the calls when the BO is already signaled.
v3: use same format as trace points for context and seqno.

Signed-off-by: Christian König <[e-mail]>
Reviewed-by: Tvrtko Ursulin <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/dma-buf/dma-fence.c

···
  */
 void dma_fence_describe(struct dma_fence *fence, struct seq_file *seq)
 {
-	const char __rcu *timeline;
-	const char __rcu *driver;
+	const char __rcu *timeline = "";
+	const char __rcu *driver = "";
+	const char *signaled = "";
 
 	rcu_read_lock();
 
-	timeline = dma_fence_timeline_name(fence);
-	driver = dma_fence_driver_name(fence);
+	if (!dma_fence_is_signaled(fence)) {
+		timeline = dma_fence_timeline_name(fence);
+		driver = dma_fence_driver_name(fence);
+		signaled = "un";
+	}
 
-	seq_printf(seq, "%s %s seq %llu %ssignalled\n",
-		   rcu_dereference(driver),
-		   rcu_dereference(timeline),
-		   fence->seqno,
-		   dma_fence_is_signaled(fence) ? "" : "un");
+	seq_printf(seq, "%llu:%llu %s %s %ssignalled\n",
+		   fence->context, fence->seqno, timeline, driver,
+		   signaled);
 
 	rcu_read_unlock();
 }