1 files changed, 27 insertions, 5 deletions

diff --git a/drivers/usb/host/xhci-hcd.c b/drivers/usb/host/xhci-hcd.c
index 0d5a8564ed17..5e92c72df642 100644
--- a/drivers/usb/host/xhci-hcd.c
+++ b/drivers/usb/host/xhci-hcd.c
@@ -1262,13 +1262,35 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
                         LAST_CTX_TO_EP_NUM(slot_ctx->dev_info));
 
         xhci_zero_in_ctx(xhci, virt_dev);
-        /* Free any old rings */
+        /* Install new rings and free or cache any old rings */
         for (i = 1; i < 31; ++i) {
-                if (virt_dev->eps[i].new_ring) {
-                        xhci_ring_free(xhci, virt_dev->eps[i].ring);
-                        virt_dev->eps[i].ring = virt_dev->eps[i].new_ring;
-                        virt_dev->eps[i].new_ring = NULL;
+                int rings_cached;
+
+                if (!virt_dev->eps[i].new_ring)
+                        continue;
+                /* Only cache or free the old ring if it exists.
+                 * It may not if this is the first add of an endpoint.
+                 */
+                if (virt_dev->eps[i].ring) {
+                        rings_cached = virt_dev->num_rings_cached;
+                        if (rings_cached < XHCI_MAX_RINGS_CACHED) {
+                                virt_dev->num_rings_cached++;
+                                rings_cached = virt_dev->num_rings_cached;
+                                virt_dev->ring_cache[rings_cached] =
+                                        virt_dev->eps[i].ring;
+                                xhci_dbg(xhci, "Cached old ring, "
+                                                "%d ring%s cached\n",
+                                                rings_cached,
+                                                (rings_cached > 1) ? "s" : "");
+                        } else {
+                                xhci_ring_free(xhci, virt_dev->eps[i].ring);
+                                xhci_dbg(xhci, "Ring cache full (%d rings), "
+                                                "freeing ring\n",
+                                                virt_dev->num_rings_cached);
+                        }
                 }
+                virt_dev->eps[i].ring = virt_dev->eps[i].new_ring;
+                virt_dev->eps[i].new_ring = NULL;
         }
 
         return ret;