serial: core: Consider rs485 settings to drive RTS

Previously the rs485 settings weren't considered when setting the RTS
line, so e.g. closing and reopening a port made serial_core to drive
the line as if rs485 was disabled.

This patch fixes those issues.

Signed-off-by: Rafael Gago Castano <rgc@hms.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 220e1d088c9b2a6348a18bf7adffadfb0fc72af8..3a14cccbd7fffd6428d0a833afabe3045d017d09 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -165,6 +165,27 @@ uart_update_mctrl(struct uart_port *port, unsigned int set, unsigned int clear)
 #define uart_set_mctrl(port, set)      uart_update_mctrl(port, set, 0)
 #define uart_clear_mctrl(port, clear)  uart_update_mctrl(port, 0, clear)
 
+static void uart_port_dtr_rts(struct uart_port *uport, int raise)
+{
+       int rs485_on = uport->rs485_config &&
+               (uport->rs485.flags & SER_RS485_ENABLED);
+       int RTS_after_send = !!(uport->rs485.flags & SER_RS485_RTS_AFTER_SEND);
+
+       if (raise) {
+               if (rs485_on && !RTS_after_send) {
+                       uart_set_mctrl(uport, TIOCM_DTR);
+                       uart_clear_mctrl(uport, TIOCM_RTS);
+               } else {
+                       uart_set_mctrl(uport, TIOCM_DTR | TIOCM_RTS);
+               }
+       } else {
+               unsigned int clear = TIOCM_DTR;
+
+               clear |= (!rs485_on || !RTS_after_send) ? TIOCM_RTS : 0;
+               uart_clear_mctrl(uport, clear);
+       }
+}
+
 /*
  * Startup the port.  This will be called once per open.  All calls
  * will be serialised by the per-port mutex.
@@ -214,7 +235,7 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
                 * port is open and ready to respond.
                 */
                if (init_hw && C_BAUD(tty))
-                       uart_set_mctrl(uport, TIOCM_RTS | TIOCM_DTR);
+                       uart_port_dtr_rts(uport, 1);
        }
 
        /*
@@ -272,7 +293,7 @@ static void uart_shutdown(struct tty_struct *tty, struct uart_state *state)
                        uport->cons->cflag = tty->termios.c_cflag;
 
                if (!tty || C_HUPCL(tty))
-                       uart_clear_mctrl(uport, TIOCM_DTR | TIOCM_RTS);
+                       uart_port_dtr_rts(uport, 0);
 
                uart_port_shutdown(port);
        }
@@ -1658,7 +1679,7 @@ static int uart_carrier_raised(struct tty_port *port)
        return 0;
 }
 
-static void uart_dtr_rts(struct tty_port *port, int onoff)
+static void uart_dtr_rts(struct tty_port *port, int raise)
 {
        struct uart_state *state = container_of(port, struct uart_state, port);
        struct uart_port *uport;
@@ -1666,12 +1687,7 @@ static void uart_dtr_rts(struct tty_port *port, int onoff)
        uport = uart_port_ref(state);
        if (!uport)
                return;
-
-       if (onoff)
-               uart_set_mctrl(uport, TIOCM_DTR | TIOCM_RTS);
-       else
-               uart_clear_mctrl(uport, TIOCM_DTR | TIOCM_RTS);
-
+       uart_port_dtr_rts(uport, raise);
        uart_port_deref(uport);
 }