[SERIAL] Clean up and fix tty transmission start/stoping

The start_tx and stop_tx methods were passed a flag to indicate
whether the start/stop was from the tty start/stop callbacks, and
some drivers used this flag to decide whether to ask the UART to
immediately stop transmission (where the UART supports such a
feature.)

There are other cases when we wish this to occur - when CTS is
lowered, or if we change from soft to hard flow control and CTS
is inactive.  In these cases, this flag was false, and we would
allow the transmitter to drain before stopping.

There is really only one case where we want to let the transmitter
drain before disabling, and that's when we run out of characters
to send.

Hence, re-jig the start_tx and stop_tx methods to eliminate this
flag, and introduce new functions for the special "disable and
allow transmitter to drain" case.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 3 insertions, 5 deletions

diff --git a/drivers/serial/sn_console.c b/drivers/serial/sn_console.c
index 12d1f14e78ce..313f9df24a2d 100644
--- a/drivers/serial/sn_console.c
+++ b/drivers/serial/sn_console.c
@@ -259,10 +259,9 @@ static unsigned int snp_tx_empty(struct uart_port *port)
 /**
  * snp_stop_tx - stop the transmitter - no-op for us
  * @port: Port to operat eon - we ignore - no-op function
- * @tty_stop: Set to 1 if called via uart_stop
  *
  */
-static void snp_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void snp_stop_tx(struct uart_port *port)
 {
 }
 
@@ -325,10 +324,9 @@ static void snp_stop_rx(struct uart_port *port)
 /**
  * snp_start_tx - Start transmitter
  * @port: Port to operate on
- * @tty_stop: Set to 1 if called via uart_start
  *
  */
-static void snp_start_tx(struct uart_port *port, unsigned int tty_stop)
+static void snp_start_tx(struct uart_port *port)
 {
         if (sal_console_port.sc_ops->sal_wakeup_transmit)
                 sal_console_port.sc_ops->sal_wakeup_transmit(&sal_console_port,
@@ -615,7 +613,7 @@ static void sn_transmit_chars(struct sn_cons_port *port, int raw)
                 uart_write_wakeup(&port->sc_port);
 
         if (uart_circ_empty(xmit))
-                snp_stop_tx(&port->sc_port, 0); /* no-op for us */
+                snp_stop_tx(&port->sc_port);    /* no-op for us */
 }
 
 /**