[PATCH 4/5] usb: xhci: Shorten the TD skipping loop

[Michal Pecio <michal.pecio@gmail.com>]

Half of this loop is code which only executes once to deal with cases
where no TD matches the event and then it returns. This code needs not
to be in any kind of loop, so get it out.

Optimize conditionals remaining in the loop body.

Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
---
 drivers/usb/host/xhci-ring.c | 69 +++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 36 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 8270c63ec3bf..1f0cb6a701c5 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2843,10 +2843,9 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 		td = list_first_entry(&ep_ring->td_list, struct xhci_td,
 				      td_list);
 
-		/* Is this TRB not part of the currently executing TD? */
-		if (!trb_in_td(td, ep_trb_dma)) {
+		if (ep->skip) {
 
-			if (ep->skip) {
+			if (!trb_in_td(td, ep_trb_dma)) {
 				/* this event is unlikely to match any TD, don't skip them all */
 				if (trb_comp_code == COMP_STOPPED_LENGTH_INVALID)
 					return 0;
@@ -2884,38 +2883,6 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 				goto check_endpoint_halted;
 			}
 
-			/* TD was queued after xrun, maybe xrun was on a link, don't panic yet */
-			if (ring_xrun_event)
-				return 0;
-
-			/*
-			 * Skip the Force Stopped Event. The 'ep_trb' of FSE is not in the current
-			 * TD pointed by 'ep_ring->dequeue' because that the hardware dequeue
-			 * pointer still at the previous TRB of the current TD. The previous TRB
-			 * maybe a Link TD or the last TRB of the previous TD. The command
-			 * completion handle will take care the rest.
-			 */
-			if (trb_comp_code == COMP_STOPPED ||
-			    trb_comp_code == COMP_STOPPED_LENGTH_INVALID) {
-				return 0;
-			}
-
-			/*
-			 * Some hosts give a spurious success event after a short
-			 * transfer or error on last TRB. Ignore it.
-			 */
-			if (xhci_spurious_success_tx_event(xhci, ep_ring)) {
-				xhci_dbg(xhci, "Spurious event dma %pad, comp_code %u after %u\n",
-					 &ep_trb_dma, trb_comp_code, ep_ring->old_trb_comp_code);
-				ep_ring->old_trb_comp_code = 0;
-				return 0;
-			}
-
-			/* HC is busted, give up! */
-			goto debug_finding_td;
-		}
-
-		if (ep->skip) {
 			xhci_dbg(xhci,
 				 "Found td. Clear skip flag for slot %u ep %u.\n",
 				 slot_id, ep_index);
@@ -2932,10 +2899,40 @@ static int handle_tx_event(struct xhci_hcd *xhci,
 
 	ep_ring->old_trb_comp_code = trb_comp_code;
 
-	/* Get out if a TD was queued at enqueue after the xrun occurred */
+	/*
+	 * Underrun handling ends here. Any TD pointed by the event was enqueued after the event
+	 * occurred, so wait for its completion now. And it's not a bug if no such TD exists.
+	 */
 	if (ring_xrun_event)
 		return 0;
 
+	/* Handle events not referencing the current TD */
+	if (!trb_in_td(td, ep_trb_dma)) {
+		/*
+		 * Skip the Force Stopped Event. The 'ep_trb' of FSE is not in the current
+		 * TD pointed by 'ep_ring->dequeue' because that the hardware dequeue
+		 * pointer still at the previous TRB of the current TD. The previous TRB
+		 * maybe a Link TD or the last TRB of the previous TD. The command
+		 * completion handle will take care the rest.
+		 */
+		if (trb_comp_code == COMP_STOPPED || trb_comp_code == COMP_STOPPED_LENGTH_INVALID)
+			return 0;
+
+		/*
+		 * Some hosts give a spurious success event after a short
+		 * transfer or error on last TRB. Ignore it.
+		 */
+		if (xhci_spurious_success_tx_event(xhci, ep_ring)) {
+			xhci_dbg(xhci, "Spurious event dma %pad, comp_code %u after %u\n",
+					&ep_trb_dma, trb_comp_code, ep_ring->old_trb_comp_code);
+			ep_ring->old_trb_comp_code = 0;
+			return 0;
+		}
+
+		/* HC is busted, give up! */
+		goto debug_finding_td;
+	}
+
 	trace_xhci_handle_transfer(ep_ring, (struct xhci_generic_trb *) ep_trb, ep_trb_dma);
 
 	/*
-- 
2.48.1