xHCI: check enqueue pointer advance into dequeue seg

When a urb is submitted to xHCI driver, check if queueing the urb will make
the enqueue pointer advance into dequeue seg and expand the ring if it
occurs. This is to guarantee the safety of ring expansion.
Signed-off-by: NAndiry Xu <andiry.xu@amd.com>
Signed-off-by: NSarah Sharp <sarah.a.sharp@linux.intel.com>
Tested-by: NPaul Zimmerman <Paul.Zimmerman@synopsys.com>

drivers/usb/host/xhci-ring.c

@@ -249,16 +249,24 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
 }
 
 /*
- * Check to see if there's room to enqueue num_trbs on the ring.  See rules
- * above.
+ * Check to see if there's room to enqueue num_trbs on the ring and make sure
+ * enqueue pointer will not advance into dequeue segment. See rules above.
  */
 static inline int room_on_ring(struct xhci_hcd *xhci, struct xhci_ring *ring,
 		unsigned int num_trbs)
 {
-	if (ring->num_trbs_free >= num_trbs)
-		return 1;
+	int num_trbs_in_deq_seg;
 
-	return 0;
+	if (ring->num_trbs_free < num_trbs)
+		return 0;
+
+	if (ring->type != TYPE_COMMAND && ring->type != TYPE_EVENT) {
+		num_trbs_in_deq_seg = ring->dequeue - ring->deq_seg->trbs;
+		if (ring->num_trbs_free < num_trbs + num_trbs_in_deq_seg)
+			return 0;
+	}
+
+	return 1;
 }
 
 /* Ring the host controller doorbell after placing a command on the ring */
@@ -2529,13 +2537,6 @@ static int prepare_ring(struct xhci_hcd *xhci, struct xhci_ring *ep_ring,
 			return -ENOMEM;
 		}
 
-		if (ep_ring->enq_seg == ep_ring->deq_seg &&
-				ep_ring->dequeue > ep_ring->enqueue) {
-			xhci_err(xhci, "Can not expand the ring while dequeue "
-				"pointer has not passed the link TRB\n");
-			return -ENOMEM;
-		}
-
 		xhci_dbg(xhci, "ERROR no room on ep ring, "
 					"try ring expansion\n");
 		num_trbs_needed = num_trbs - ep_ring->num_trbs_free;