[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, 4 insertions, 6 deletions

diff --git a/drivers/serial/s3c2410.c b/drivers/serial/s3c2410.c
index 7365d4b50b95..c361c6fb0809 100644
--- a/drivers/serial/s3c2410.c
+++ b/drivers/serial/s3c2410.c
@@ -246,8 +246,7 @@ static void s3c24xx_serial_rx_disable(struct uart_port *port)
 	spin_unlock_irqrestore(&port->lock, flags);
 }
 
-static void
-s3c24xx_serial_stop_tx(struct uart_port *port, unsigned int tty_stop)
+static void s3c24xx_serial_stop_tx(struct uart_port *port)
 {
 	if (tx_enabled(port)) {
 		disable_irq(TX_IRQ(port));
@@ -257,8 +256,7 @@ s3c24xx_serial_stop_tx(struct uart_port *port, unsigned int tty_stop)
 	}
 }
 
-static void
-s3c24xx_serial_start_tx(struct uart_port *port, unsigned int tty_start)
+static void s3c24xx_serial_start_tx(struct uart_port *port)
 {
 	if (!tx_enabled(port)) {
 		if (port->flags & UPF_CONS_FLOW)
@@ -424,7 +422,7 @@ static irqreturn_t s3c24xx_serial_tx_chars(int irq, void *id, struct pt_regs *re
 	*/
 
 	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
-		s3c24xx_serial_stop_tx(port, 0);
+		s3c24xx_serial_stop_tx(port);
 		goto out;
 	}
 
@@ -443,7 +441,7 @@ static irqreturn_t s3c24xx_serial_tx_chars(int irq, void *id, struct pt_regs *re
 		uart_write_wakeup(port);
 
 	if (uart_circ_empty(xmit))
-		s3c24xx_serial_stop_tx(port, 0);
+		s3c24xx_serial_stop_tx(port);
 
  out:
 	return IRQ_HANDLED;