tty/serial: at91: RS485 mode: 0 is valid for delay_rts_after_send

commit 8687634b7908c42eb700e0469e110e02833611d1 upstream.

In RS485 mode, we may want to set the delay_rts_after_send value to 0.
In the datasheet, the 0 value is said to "disable" the Transmitter Timeguard but
this is exactly the expected behavior if we want no delay...

Moreover, if the value was set to non-zero value by device-tree or earlier
ioctl command, it was impossible to change it back to zero.

Reported-by: Sami Pietikäinen <Sami.Pietikainen@wapice.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 99fcb8c..9645186 100644 (file)
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -229,8 +229,7 @@ void atmel_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf)
        if (rs485conf->flags & SER_RS485_ENABLED) {
                dev_dbg(port->dev, "Setting UART to RS485\n");
                atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
-               if ((rs485conf->delay_rts_after_send) > 0)
-                       UART_PUT_TTGR(port, rs485conf->delay_rts_after_send);
+               UART_PUT_TTGR(port, rs485conf->delay_rts_after_send);
                mode |= ATMEL_US_USMODE_RS485;
        } else {
                dev_dbg(port->dev, "Setting UART to RS232\n");
@@ -305,9 +304,7 @@ static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
 
        if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
                dev_dbg(port->dev, "Setting UART to RS485\n");
-               if ((atmel_port->rs485.delay_rts_after_send) > 0)
-                       UART_PUT_TTGR(port,
-                                       atmel_port->rs485.delay_rts_after_send);
+               UART_PUT_TTGR(port, atmel_port->rs485.delay_rts_after_send);
                mode |= ATMEL_US_USMODE_RS485;
        } else {
                dev_dbg(port->dev, "Setting UART to RS232\n");
@@ -1229,9 +1226,7 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 
        if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
                dev_dbg(port->dev, "Setting UART to RS485\n");
-               if ((atmel_port->rs485.delay_rts_after_send) > 0)
-                       UART_PUT_TTGR(port,
-                                       atmel_port->rs485.delay_rts_after_send);
+               UART_PUT_TTGR(port, atmel_port->rs485.delay_rts_after_send);
                mode |= ATMEL_US_USMODE_RS485;
        } else {
                dev_dbg(port->dev, "Setting UART to RS232\n");