USB: serial: io_ti: use irqsave() in USB's complete callback

The USB completion callback does not disable interrupts while acquiring
the lock. We want to remove the local_irq_disable() invocation from
__usb_hcd_giveback_urb() and therefore it is required for the callback
handler to disable the interrupts while acquiring the lock.
The callback may be invoked either in IRQ or BH context depending on the
USB host controller.
Use the _irqsave() variant of the locking primitives.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/io_ti.c

@@ -1729,6 +1729,7 @@ static void edge_bulk_in_callback(struct urb *urb)
 	struct edgeport_port *edge_port = urb->context;
 	struct device *dev = &edge_port->port->dev;
 	unsigned char *data = urb->transfer_buffer;
+	unsigned long flags;
 	int retval = 0;
 	int port_number;
 	int status = urb->status;
@@ -1780,13 +1781,13 @@ static void edge_bulk_in_callback(struct urb *urb)
 
 exit:
 	/* continue read unless stopped */
-	spin_lock(&edge_port->ep_lock);
+	spin_lock_irqsave(&edge_port->ep_lock, flags);
 	if (edge_port->ep_read_urb_state == EDGE_READ_URB_RUNNING)
 		retval = usb_submit_urb(urb, GFP_ATOMIC);
 	else if (edge_port->ep_read_urb_state == EDGE_READ_URB_STOPPING)
 		edge_port->ep_read_urb_state = EDGE_READ_URB_STOPPED;
 
-	spin_unlock(&edge_port->ep_lock);
+	spin_unlock_irqrestore(&edge_port->ep_lock, flags);
 	if (retval)
 		dev_err(dev, "%s - usb_submit_urb failed with result %d\n", __func__, retval);
 }