serial: pl011: Fix incorrect rs485 RTS polarity on set_mctrl

Commit 8d479237727c ("serial: amba-pl011: add RS485 support") sought to
keep RTS deasserted on set_mctrl if rs485 is enabled.  However it did so
only if deasserted RTS polarity is high.  Fix it in case it's low.

Fixes: 8d479237727c ("serial: amba-pl011: add RS485 support")
Cc: stable@vger.kernel.org # v5.15+
Cc: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Jochen Mades <jochen@mades.net>
[lukas: copyedit commit message, add stable designation]
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/85fa3323ba8c307943969b7343e23f34c3e652ba.1642909284.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 1f1df46..f64c475 100644 (file)
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1582,8 +1582,12 @@ static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl)
            container_of(port, struct uart_amba_port, port);
        unsigned int cr;
 
-       if (port->rs485.flags & SER_RS485_ENABLED)
-               mctrl &= ~TIOCM_RTS;
+       if (port->rs485.flags & SER_RS485_ENABLED) {
+               if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
+                       mctrl &= ~TIOCM_RTS;
+               else
+                       mctrl |= TIOCM_RTS;
+       }
 
        cr = pl011_read(uap, REG_CR);