[PATCH][for 4.14] xhci: allow TRACE to work with EVENT ring dequeue

[Adam Wallis]

inc_deq() currently bails earlier for EVENT rings than the common return
point of the function, due to the fact that EVENT rings do not have
link TRBs. The unfortunate side effect of this is that the very useful
trace_xhci_inc_deq() function is not called/usable for EVENT ring
debug.

This patch provides a refactor by removing the multiple return exit
points into a single return which additionally allows for all rings to
use the trace function.

Signed-off-by: Adam Wallis <awallis at codeaurora.org>
---
 drivers/usb/host/xhci-ring.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index a944365..10afd50 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -171,25 +171,24 @@ static void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring)
 	if (ring->type == TYPE_EVENT) {
 		if (!last_trb_on_seg(ring->deq_seg, ring->dequeue)) {
 			ring->dequeue++;
-			return;
+		} else {
+			if (last_trb_on_ring(ring, ring->deq_seg,
+				ring->dequeue))
+				ring->cycle_state ^= 1;
+			ring->deq_seg = ring->deq_seg->next;
+			ring->dequeue = ring->deq_seg->trbs;
+		}
+	} else {
+		/* All other rings have link trbs */
+		if (!trb_is_link(ring->dequeue)) {
+			ring->dequeue++;
+			ring->num_trbs_free++;
+		}
+		while (trb_is_link(ring->dequeue)) {
+			ring->deq_seg = ring->deq_seg->next;
+			ring->dequeue = ring->deq_seg->trbs;
 		}
-		if (last_trb_on_ring(ring, ring->deq_seg, ring->dequeue))
-			ring->cycle_state ^= 1;
-		ring->deq_seg = ring->deq_seg->next;
-		ring->dequeue = ring->deq_seg->trbs;
-		return;
-	}
-
-	/* All other rings have link trbs */
-	if (!trb_is_link(ring->dequeue)) {
-		ring->dequeue++;
-		ring->num_trbs_free++;
-	}
-	while (trb_is_link(ring->dequeue)) {
-		ring->deq_seg = ring->deq_seg->next;
-		ring->dequeue = ring->deq_seg->trbs;
 	}
-
 	trace_xhci_inc_deq(ring);
 
 	return;
-- 
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