xhci: use and add separate function for checking for link trbs

Add a new is_link_trb() function that only checks for link trbs.
We want to split generic last_trb() function which is used for both
event rings without link trbs, and endpoint and command rings with links.

This will allow us to easier check for link trbs added mid segments.
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-ring.c

@@ -115,6 +115,11 @@ static int last_trb(struct xhci_hcd *xhci, struct xhci_ring *ring,
 		return TRB_TYPE_LINK_LE32(trb->link.control);
 }
 
+static bool trb_is_link(union xhci_trb *trb)
+{
+	return TRB_TYPE_LINK_LE32(trb->link.control);
+}
+
 static int enqueue_is_link_trb(struct xhci_ring *ring)
 {
 	struct xhci_link_trb *link = &ring->enqueue->link;
@@ -130,7 +135,7 @@ static void next_trb(struct xhci_hcd *xhci,
 		struct xhci_segment **seg,
 		union xhci_trb **trb)
 {
-	if (last_trb(xhci, ring, *seg, *trb)) {
+	if (trb_is_link(*trb)) {
 		*seg = (*seg)->next;
 		*trb = ((*seg)->trbs);
 	} else {
@@ -150,8 +155,7 @@ static void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring)
 	 * If this is not event ring, and the dequeue pointer
 	 * is not on a link TRB, there is one more usable TRB
 	 */
-	if (ring->type != TYPE_EVENT &&
-			!last_trb(xhci, ring, ring->deq_seg, ring->dequeue))
+	if (ring->type != TYPE_EVENT && !trb_is_link(ring->dequeue))
 		ring->num_trbs_free++;
 
 	do {
@@ -199,13 +203,13 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
 
 	chain = le32_to_cpu(ring->enqueue->generic.field[3]) & TRB_CHAIN;
 	/* If this is not event ring, there is one less usable TRB */
-	if (!last_trb(xhci, ring, ring->enq_seg, ring->enqueue))
+	if (!trb_is_link(ring->enqueue))
 		ring->num_trbs_free--;
 	next = ++(ring->enqueue);
 
 	ring->enq_updates++;
 	/* Update the dequeue pointer further if that was a link TRB */
-	while (last_trb(xhci, ring, ring->enq_seg, next)) {
+	while (trb_is_link(next)) {
 
 		/*
 		 * If the caller doesn't plan on enqueueing more TDs before
@@ -940,7 +944,7 @@ static void update_ring_for_set_deq_completion(struct xhci_hcd *xhci,
 	 * the dequeue pointer one segment further, or we'll jump off
 	 * the segment into la-la-land.
 	 */
-	if (last_trb(xhci, ep_ring, ep_ring->deq_seg, ep_ring->dequeue)) {
+	if (trb_is_link(ep_ring->dequeue)) {
 		ep_ring->deq_seg = ep_ring->deq_seg->next;
 		ep_ring->dequeue = ep_ring->deq_seg->trbs;
 	}
@@ -949,8 +953,7 @@ static void update_ring_for_set_deq_completion(struct xhci_hcd *xhci,
 		/* We have more usable TRBs */
 		ep_ring->num_trbs_free++;
 		ep_ring->dequeue++;
-		if (last_trb(xhci, ep_ring, ep_ring->deq_seg,
-				ep_ring->dequeue)) {
+		if (trb_is_link(ep_ring->dequeue)) {
 			if (ep_ring->dequeue ==
 					dev->eps[ep_index].queued_deq_ptr)
 				break;
@@ -2898,7 +2901,7 @@ static int prepare_ring(struct xhci_hcd *xhci, struct xhci_ring *ep_ring,
 
 		next = ring->enqueue;
 
-		while (last_trb(xhci, ring, ring->enq_seg, next)) {
+		while (trb_is_link(next)) {
 			/* If we're not dealing with 0.95 hardware or isoc rings
 			 * on AMD 0.96 host, clear the chain bit.
 			 */
@@ -3287,8 +3290,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		 */
 		if (enqd_len + trb_buff_len < full_len) {
 			field |= TRB_CHAIN;
-			if (last_trb(xhci, ring, ring->enq_seg,
-				     ring->enqueue + 1)) {
+			if (trb_is_link(ring->enqueue + 1)) {
 				if (xhci_align_td(xhci, urb, enqd_len,
 						  &trb_buff_len,
 						  ring->enq_seg)) {