SERIAL: omap: fix set_mctrl() breakage

c538d20c7f (and maybe previous commits) broke set_mctrl() by making
it only capable of setting bits in the MCR register.  This prevents
software controlled flow control and modem control line manipulation
via TIOCMSET/TIOCMBIC from working correctly.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 6ef4cc49d81e..fb06def4d982 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -504,7 +504,7 @@ static unsigned int serial_omap_get_mctrl(struct uart_port *port)
 static void serial_omap_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
         struct uart_omap_port *up = to_uart_omap_port(port);
-        unsigned char mcr = 0;
+        unsigned char mcr = 0, old_mcr;
 
         dev_dbg(up->port.dev, "serial_omap_set_mctrl+%d\n", up->port.line);
         if (mctrl & TIOCM_RTS)
@@ -519,8 +519,10 @@ static void serial_omap_set_mctrl(struct uart_port *port, unsigned int mctrl)
                 mcr |= UART_MCR_LOOP;
 
         pm_runtime_get_sync(up->dev);
-        up->mcr = serial_in(up, UART_MCR);
-        up->mcr |= mcr;
+        old_mcr = serial_in(up, UART_MCR);
+        old_mcr &= ~(UART_MCR_LOOP | UART_MCR_OUT2 | UART_MCR_OUT1 |
+                     UART_MCR_DTR | UART_MCR_RTS);
+        up->mcr = old_mcr | mcr;
         serial_out(up, UART_MCR, up->mcr);
         pm_runtime_mark_last_busy(up->dev);
         pm_runtime_put_autosuspend(up->dev);