usb: xhci: Don't try to recover an endpoint if port is in error state.

A USB3 device needs to be reset and re-enumarated if the port it
connects to goes to a error state, with link state inactive.

There is no use in trying to recover failed transactions by resetting
endpoints at this stage. Tests show that in rare cases, after multiple
endpoint resets of a roothub port the whole host controller might stop
completely.

Several retries to recover from transaction error can happen as
it can take a long time before the hub thread discovers the USB3
port error and inactive link.

We can't reliably detect the port error from slot or endpoint context
due to a limitation in xhci, see xhci specs section 4.8.3:
"There are several cases where the EP State field in the Output
Endpoint Context may not reflect the current state of an endpoint"
and
"Software should maintain an accurate value for EP State, by tracking it
with an internal variable that is driven by Events and Doorbell accesses"

Same appears to be true for slot state.

set a flag to the corresponding slot if a USB3 roothub port link goes
inactive to prevent both queueing new URBs and resetting endpoints.

Reported-by: Rapolu Chiranjeevi <chiranjeevi.rapolu@intel.com>
Tested-by: Rapolu Chiranjeevi <chiranjeevi.rapolu@intel.com>
Cc: <stable@vger.kernel.org>
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

@@ -1612,8 +1612,13 @@ static void handle_port_status(struct xhci_hcd *xhci,
 		usb_hcd_resume_root_hub(hcd);
 	}
 
-	if (hcd->speed >= HCD_USB3 && (portsc & PORT_PLS_MASK) == XDEV_INACTIVE)
+	if (hcd->speed >= HCD_USB3 &&
+	    (portsc & PORT_PLS_MASK) == XDEV_INACTIVE) {
+		slot_id = xhci_find_slot_id_by_port(hcd, xhci, hcd_portnum + 1);
+		if (slot_id && xhci->devs[slot_id])
+			xhci->devs[slot_id]->flags |= VDEV_PORT_ERROR;
 		bus_state->port_remote_wakeup &= ~(1 << hcd_portnum);
+	}
 
 	if ((portsc & PORT_PLC) && (portsc & PORT_PLS_MASK) == XDEV_RESUME) {
 		xhci_dbg(xhci, "port resume event for port %d\n", port_id);
@@ -1801,6 +1806,14 @@ static void xhci_cleanup_halted_endpoint(struct xhci_hcd *xhci,
 {
 	struct xhci_virt_ep *ep = &xhci->devs[slot_id]->eps[ep_index];
 	struct xhci_command *command;
+
+	/*
+	 * Avoid resetting endpoint if link is inactive. Can cause host hang.
+	 * Device will be reset soon to recover the link so don't do anything
+	 */
+	if (xhci->devs[slot_id]->flags & VDEV_PORT_ERROR)
+		return;
+
 	command = xhci_alloc_command(xhci, false, GFP_ATOMIC);
 	if (!command)
 		return;