SERIAL: core: add hardware assisted h/w flow control support

Ports which are handling h/w flow control in hardware must not have
their RTS state altered depending on the tty's hardware-stopped state.
Avoid this additional logic when setting the termios state.

Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 7 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);