xhci: Don't submit commands when the host is dead.

When the xHCI host controller dies, the USB core may attempt to reset the
devices to their default configuration before disconnecting them.  This
causes calls into the xHCI bandwidth allocation functions.  Don't allow
those functions to submit commands or work on xHCI structures if the host
controller is marked as dying.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/xhci.c

@@ -1314,8 +1314,10 @@ int xhci_drop_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
 	if (ret <= 0)
 		return ret;
 	xhci = hcd_to_xhci(hcd);
-	xhci_dbg(xhci, "%s called for udev %p\n", __func__, udev);
+	if (xhci->xhc_state & XHCI_STATE_DYING)
+		return -ENODEV;
 
+	xhci_dbg(xhci, "%s called for udev %p\n", __func__, udev);
 	drop_flag = xhci_get_endpoint_flag(&ep->desc);
 	if (drop_flag == SLOT_FLAG || drop_flag == EP0_FLAG) {
 		xhci_dbg(xhci, "xHCI %s - can't drop slot or ep 0 %#x\n",
@@ -1401,6 +1403,8 @@ int xhci_add_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
 		return ret;
 	}
 	xhci = hcd_to_xhci(hcd);
+	if (xhci->xhc_state & XHCI_STATE_DYING)
+		return -ENODEV;
 
 	added_ctxs = xhci_get_endpoint_flag(&ep->desc);
 	last_ctx = xhci_last_valid_endpoint(added_ctxs);
@@ -1676,6 +1680,8 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
 	if (ret <= 0)
 		return ret;
 	xhci = hcd_to_xhci(hcd);
+	if (xhci->xhc_state & XHCI_STATE_DYING)
+		return -ENODEV;
 
 	xhci_dbg(xhci, "%s called for udev %p\n", __func__, udev);
 	virt_dev = xhci->devs[udev->slot_id];