xHCI: factor out segments allocation and free function

Factor out the segments allocation and free part from ring allocation
and free routines since driver may call them directly when try to expand
a ring.
Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Tested-by: Paul Zimmerman <Paul.Zimmerman@synopsys.com>

drivers/usb/host/xhci-mem.c

@@ -65,6 +65,20 @@ static void xhci_segment_free(struct xhci_hcd *xhci, struct xhci_segment *seg)
 	kfree(seg);
 }
 
+static void xhci_free_segments_for_ring(struct xhci_hcd *xhci,
+				struct xhci_segment *first)
+{
+	struct xhci_segment *seg;
+
+	seg = first->next;
+	while (seg != first) {
+		struct xhci_segment *next = seg->next;
+		xhci_segment_free(xhci, seg);
+		seg = next;
+	}
+	xhci_segment_free(xhci, first);
+}
+
 /*
  * Make the prev segment point to the next segment.
  *
@@ -101,22 +115,12 @@ static void xhci_link_segments(struct xhci_hcd *xhci, struct xhci_segment *prev,
 /* XXX: Do we need the hcd structure in all these functions? */
 void xhci_ring_free(struct xhci_hcd *xhci, struct xhci_ring *ring)
 {
-	struct xhci_segment *seg;
-	struct xhci_segment *first_seg;
-
 	if (!ring)
 		return;
-	if (ring->first_seg) {
-		first_seg = ring->first_seg;
-		seg = first_seg->next;
-		while (seg != first_seg) {
-			struct xhci_segment *next = seg->next;
-			xhci_segment_free(xhci, seg);
-			seg = next;
-		}
-		xhci_segment_free(xhci, first_seg);
-		ring->first_seg = NULL;
-	}
+
+	if (ring->first_seg)
+		xhci_free_segments_for_ring(xhci, ring->first_seg);
+
 	kfree(ring);
 }
 
@@ -143,6 +147,38 @@ static void xhci_initialize_ring_info(struct xhci_ring *ring)
 	ring->num_trbs_free = ring->num_segs * (TRBS_PER_SEGMENT - 1) - 1;
 }
 
+/* Allocate segments and link them for a ring */
+static int xhci_alloc_segments_for_ring(struct xhci_hcd *xhci,
+		struct xhci_segment **first, struct xhci_segment **last,
+		unsigned int num_segs, enum xhci_ring_type type, gfp_t flags)
+{
+	struct xhci_segment *prev;
+
+	prev = xhci_segment_alloc(xhci, flags);
+	if (!prev)
+		return -ENOMEM;
+	num_segs--;
+
+	*first = prev;
+	while (num_segs > 0) {
+		struct xhci_segment	*next;
+
+		next = xhci_segment_alloc(xhci, flags);
+		if (!next) {
+			xhci_free_segments_for_ring(xhci, *first);
+			return -ENOMEM;
+		}
+		xhci_link_segments(xhci, prev, next, type);
+
+		prev = next;
+		num_segs--;
+	}
+	xhci_link_segments(xhci, prev, *first, type);
+	*last = prev;
+
+	return 0;
+}
+
 /**
  * Create a new ring with zero or more segments.
  *
@@ -154,7 +190,7 @@ static struct xhci_ring *xhci_ring_alloc(struct xhci_hcd *xhci,
 		unsigned int num_segs, enum xhci_ring_type type, gfp_t flags)
 {
 	struct xhci_ring	*ring;
-	struct xhci_segment	*prev;
+	int ret;
 
 	ring = kzalloc(sizeof *(ring), flags);
 	if (!ring)
@@ -166,30 +202,15 @@ static struct xhci_ring *xhci_ring_alloc(struct xhci_hcd *xhci,
 	if (num_segs == 0)
 		return ring;
 
-	ring->first_seg = xhci_segment_alloc(xhci, flags);
-	if (!ring->first_seg)
+	ret = xhci_alloc_segments_for_ring(xhci, &ring->first_seg,
+			&ring->last_seg, num_segs, type, flags);
+	if (ret)
 		goto fail;
-	num_segs--;
-
-	prev = ring->first_seg;
-	while (num_segs > 0) {
-		struct xhci_segment	*next;
-
-		next = xhci_segment_alloc(xhci, flags);
-		if (!next)
-			goto fail;
-		xhci_link_segments(xhci, prev, next, type);
-
-		prev = next;
-		num_segs--;
-	}
-	xhci_link_segments(xhci, prev, ring->first_seg, type);
-	ring->last_seg = prev;
 
 	/* Only event ring does not use link TRB */
 	if (type != TYPE_EVENT) {
 		/* See section 4.9.2.1 and 6.4.4.1 */
-		prev->trbs[TRBS_PER_SEGMENT-1].link.control |=
+		ring->last_seg->trbs[TRBS_PER_SEGMENT - 1].link.control |=
 			cpu_to_le32(LINK_TOGGLE);
 	}
 	xhci_initialize_ring_info(ring);