3 files changed, 14 insertions, 0 deletions

diff --git a/Documentation/serial/driver b/Documentation/serial/driver
index 88ad615dd338..77ba0afbe4db 100644
--- a/Documentation/serial/driver
+++ b/Documentation/serial/driver
@@ -186,6 +186,17 @@ hardware.
         Locking: port_sem taken.
         Interrupts: caller dependent.
 
+  flush_buffer(port)
+        Flush any write buffers, reset any DMA state and stop any
+        ongoing DMA transfers.
+
+        This will be called whenever the port->info->xmit circular
+        buffer is cleared.
+
+        Locking: port->lock taken.
+        Interrupts: locally disabled.
+        This call must not sleep
+
   set_termios(port,termios,oldtermios)
         Change the port parameters, including word length, parity, stop
         bits.  Update read_status_mask and ignore_status_mask to indicate
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 42d2e108b679..9884bc9eecb1 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -573,6 +573,8 @@ static void uart_flush_buffer(struct tty_struct *tty)
 
         spin_lock_irqsave(&port->lock, flags);
         uart_circ_clear(&state->info->xmit);
+        if (port->ops->flush_buffer)
+                port->ops->flush_buffer(port);
         spin_unlock_irqrestore(&port->lock, flags);
         tty_wakeup(tty);
 }
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index d8f31de632c5..1d2faa6592ae 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -190,6 +190,7 @@ struct uart_ops {
         void            (*break_ctl)(struct uart_port *, int ctl);
         int             (*startup)(struct uart_port *);
         void            (*shutdown)(struct uart_port *);
+        void            (*flush_buffer)(struct uart_port *);
         void            (*set_termios)(struct uart_port *, struct ktermios *new,
                                        struct ktermios *old);
         void            (*set_ldisc)(struct uart_port *);