2 files changed, 9 insertions, 0 deletions

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index bd10bbd56446..9d8796e77188 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1255,6 +1255,13 @@ static void uart_set_termios(struct tty_struct *tty,
                 uart_set_mctrl(uport, mask);
         }
 
+        /*
+         * If the port is doing h/w assisted flow control, do nothing.
+         * We assume that tty->hw_stopped has never been set.
+         */
+        if (uport->flags & UPF_HARD_FLOW)
+                return;
+
         /* Handle turning off CRTSCTS */
         if ((old_termios->c_cflag & CRTSCTS) && !(cflag & CRTSCTS)) {
                 spin_lock_irqsave(&uport->lock, flags);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 00051388de3c..e2cda5d04e48 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -163,6 +163,8 @@ struct uart_port {
 #define UPF_BUGGY_UART          ((__force upf_t) (1 << 14))
 #define UPF_NO_TXEN_TEST        ((__force upf_t) (1 << 15))
 #define UPF_MAGIC_MULTIPLIER    ((__force upf_t) (1 << 16))
+/* Port has hardware-assisted h/w flow control (iow, auto-RTS *not* auto-CTS) */
+#define UPF_HARD_FLOW           ((__force upf_t) (1 << 21))
 /* Port has hardware-assisted s/w flow control */
 #define UPF_SOFT_FLOW           ((__force upf_t) (1 << 22))
 #define UPF_CONS_FLOW           ((__force upf_t) (1 << 23))