tty: serial: 8250_core: allow to set ->throttle / ->unthrottle callbacks

The OMAP UART provides support for HW assisted flow control. What is
missing is the support to throttle / unthrottle callbacks which are used
by the omap-serial driver at the moment.
This patch adds the callbacks. It should be safe to add them since they
are only invoked from the serial_core (uart_throttle()) if the feature
flags are set.

Reviewed-by: Tony Lindgren <tony@atomide.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index a0c1d64f34c5..68c44d97091b 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1319,6 +1319,16 @@ static void serial8250_start_tx(struct uart_port *port)
         }
 }
 
+static void serial8250_throttle(struct uart_port *port)
+{
+        port->throttle(port);
+}
+
+static void serial8250_unthrottle(struct uart_port *port)
+{
+        port->unthrottle(port);
+}
+
 static void serial8250_stop_rx(struct uart_port *port)
 {
         struct uart_8250_port *up = up_to_u8250p(port);
@@ -2912,6 +2922,8 @@ static struct uart_ops serial8250_pops = {
         .get_mctrl      = serial8250_get_mctrl,
         .stop_tx        = serial8250_stop_tx,
         .start_tx       = serial8250_start_tx,
+        .throttle       = serial8250_throttle,
+        .unthrottle     = serial8250_unthrottle,
         .stop_rx        = serial8250_stop_rx,
         .enable_ms      = serial8250_enable_ms,
         .break_ctl      = serial8250_break_ctl,
@@ -3462,6 +3474,8 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
                 uart->capabilities      = up->capabilities;
                 uart->rs485_config      = up->rs485_config;
                 uart->rs485             = up->rs485;
+                uart->port.throttle     = up->port.throttle;
+                uart->port.unthrottle   = up->port.unthrottle;
 
                 /* Take tx_loadsz from fifosize if it wasn't set separately */
                 if (uart->port.fifosize && !uart->tx_loadsz)