xhci: fix 20000ms port resume timeout

commit a54408d upstream.

A uncleared PLC (port link change) bit will prevent furuther port event
interrupts for that port. Leaving it uncleared caused get_port_status()
to timeout after 20000ms while waiting to get the final port event
interrupt for resume -> U0 state change.

This is a targeted fix for a specific case where we get a port resume event
racing with xhci resume. The port event interrupt handler notices xHC is
not yet running and bails out early, leaving PLC uncleared.

The whole xhci port resuming needs more attention, but while working on it
it anyways makes sense to always ensure PLC is cleared in get_port_status
before setting a new link state and waiting for its completion.

Signed-off-by: Mathias Nyman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: matnyman

drivers/usb/host/xhci-hub.c

@@ -768,6 +768,9 @@ static u32 xhci_get_port_status(struct usb_hcd *hcd,
 			clear_bit(wIndex, &bus_state->resuming_ports);
 
 			set_bit(wIndex, &bus_state->rexit_ports);
+
+			xhci_test_and_clear_bit(xhci, port_array, wIndex,
+						PORT_PLC);
 			xhci_set_link_state(xhci, port_array, wIndex,
 					XDEV_U0);