USB: serial: sierra driver read path bug fix

This patch fixes a problem in function sierra_indat_callback() which
would stop receiving traffic from a modem if a number of URB failures
occur.  Failed URBs are not resubmitted for the next read and there is
only a limited number of URBs allocated for the IN path. After this
number of failures, the receive path stops working on a particular
interface.
Signed-off-by: Elina Pasheva <epasheva@sierrawireless.com>

drivers/usb/serial/sierra.c

@@ -509,24 +509,30 @@ static void sierra_indat_callback(struct urb *urb)
 	unsigned char *data = urb->transfer_buffer;
 	int status = urb->status;
 
-	dbg("%s: %p", __func__, urb);
-
 	endpoint = usb_pipeendpoint(urb->pipe);
 	port = urb->context;
 
+	dev_dbg(&port->dev, "%s: %p\n", __func__, urb);
+
 	if (status) {
 		dev_dbg(&port->dev, "%s: nonzero status: %d on"
 			" endpoint %02x\n", __func__, status, endpoint);
 	} else {
 		if (urb->actual_length) {
 			tty = tty_port_tty_get(&port->port);
+
 			tty_buffer_request_room(tty, urb->actual_length);
 			tty_insert_flip_string(tty, data, urb->actual_length);
 			tty_flip_buffer_push(tty);
+
 			tty_kref_put(tty);
-		} else
+			usb_serial_debug_data(debug, &port->dev, __func__,
+				urb->actual_length, data);
+		} else {
 			dev_dbg(&port->dev, "%s: empty read urb"
 				" received\n", __func__);
+		}
+	}
 
 	/* Resubmit urb so we continue receiving */
 	if (port->port.count && status != -ESHUTDOWN && status != -EPERM) {
@@ -535,7 +541,7 @@ static void sierra_indat_callback(struct urb *urb)
 			dev_err(&port->dev, "resubmit read urb failed."
 				"(%d)\n", err);
 	}
-	}
+
 	return;
 }