xhci: free xhci virtual devices with leaf nodes first

the tt_info provided by a HS hub might be in use to by a child device
Make sure we free the devices in the correct order.

This is needed in special cases such as when xhci controller is
reset when resuming from hibernate, and all virt_devices are freed.

Also free the virt_devices starting from max slot_id as children
more commonly have higher slot_id than parent.

CC: <stable@vger.kernel.org>
Reported-by: NGuenter Roeck <groeck@chromium.org>
Tested-by: NGuenter Roeck <groeck@chromium.org>
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-mem.c

@@ -979,6 +979,40 @@ void xhci_free_virt_device(struct xhci_hcd *xhci, int slot_id)
 	xhci->devs[slot_id] = NULL;
 }
 
+/*
+ * Free a virt_device structure.
+ * If the virt_device added a tt_info (a hub) and has children pointing to
+ * that tt_info, then free the child first. Recursive.
+ * We can't rely on udev at this point to find child-parent relationships.
+ */
+void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
+{
+	struct xhci_virt_device *vdev;
+	struct list_head *tt_list_head;
+	struct xhci_tt_bw_info *tt_info, *next;
+	int i;
+
+	vdev = xhci->devs[slot_id];
+	if (!vdev)
+		return;
+
+	tt_list_head = &(xhci->rh_bw[vdev->real_port - 1].tts);
+	list_for_each_entry_safe(tt_info, next, tt_list_head, tt_list) {
+		/* is this a hub device that added a tt_info to the tts list */
+		if (tt_info->slot_id == slot_id) {
+			/* are any devices using this tt_info? */
+			for (i = 1; i < HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
+				vdev = xhci->devs[i];
+				if (vdev && (vdev->tt_info == tt_info))
+					xhci_free_virt_devices_depth_first(
+						xhci, i);
+			}
+		}
+	}
+	/* we are now at a leaf device */
+	xhci_free_virt_device(xhci, slot_id);
+}
+
 int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
 		struct usb_device *udev, gfp_t flags)
 {
@@ -1828,8 +1862,8 @@ void xhci_mem_cleanup(struct xhci_hcd *xhci)
 		}
 	}
 
-	for (i = 1; i < MAX_HC_SLOTS; ++i)
-		xhci_free_virt_device(xhci, i);
+	for (i = HCS_MAX_SLOTS(xhci->hcs_params1); i > 0; i--)
+		xhci_free_virt_devices_depth_first(xhci, i);
 
 	dma_pool_destroy(xhci->segment_pool);
 	xhci->segment_pool = NULL;