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

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>
Cc: stable@vger.kernel.org  # 3.2+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index b1fcddd..2a8f528 100644 (file)
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -316,8 +316,7 @@ static int atmel_config_rs485(struct uart_port *port,
        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");
@@ -355,8 +354,7 @@ static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
 
        /* override mode to RS485 if needed, otherwise keep the current mode */
        if (port->rs485.flags & SER_RS485_ENABLED) {
-               if ((port->rs485.delay_rts_after_send) > 0)
-                       UART_PUT_TTGR(port, port->rs485.delay_rts_after_send);
+               UART_PUT_TTGR(port, port->rs485.delay_rts_after_send);
                mode &= ~ATMEL_US_USMODE;
                mode |= ATMEL_US_USMODE_RS485;
        }
@@ -2062,8 +2060,7 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 
        /* mode */
        if (port->rs485.flags & SER_RS485_ENABLED) {
-               if ((port->rs485.delay_rts_after_send) > 0)
-                       UART_PUT_TTGR(port, port->rs485.delay_rts_after_send);
+               UART_PUT_TTGR(port, port->rs485.delay_rts_after_send);
                mode |= ATMEL_US_USMODE_RS485;
        } else if (termios->c_cflag & CRTSCTS) {
                /* RS232 with hardware handshake (RTS/CTS) */