[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, 4 deletions

diff --git a/drivers/serial/mpsc.c b/drivers/serial/mpsc.c
index e43276c6a954..efe79b1fd431 100644
--- a/drivers/serial/mpsc.c
+++ b/drivers/serial/mpsc.c
@@ -1072,18 +1072,18 @@ mpsc_get_mctrl(struct uart_port *port)
 }
 
 static void
-mpsc_stop_tx(struct uart_port *port, uint tty_start)
+mpsc_stop_tx(struct uart_port *port)
 {
         struct mpsc_port_info *pi = (struct mpsc_port_info *)port;
 
-        pr_debug("mpsc_stop_tx[%d]: tty_start: %d\n", port->line, tty_start);
+        pr_debug("mpsc_stop_tx[%d]\n", port->line);
 
         mpsc_freeze(pi);
         return;
 }
 
 static void
-mpsc_start_tx(struct uart_port *port, uint tty_start)
+mpsc_start_tx(struct uart_port *port)
 {
         struct mpsc_port_info *pi = (struct mpsc_port_info *)port;
 
@@ -1091,7 +1091,7 @@ mpsc_start_tx(struct uart_port *port, uint tty_start)
         mpsc_copy_tx_data(pi);
         mpsc_sdma_start_tx(pi);
 
-        pr_debug("mpsc_start_tx[%d]: tty_start: %d\n", port->line, tty_start);
+        pr_debug("mpsc_start_tx[%d]\n", port->line);
         return;
 }