From: Yinghai Lu <Yinghai.Lu@Sun.COM>

with reverting "x86, serial: convert legacy COM ports to platform devices",
we will have the serial console before the port is probled again.

uart_add_one_port==>uart_configure_port==>set_mcttrl(port, 0) will clear
the DTR setting by uart_set_options().  then I will lose my output from
serial console again.

So try to keep DTR in uart_configure_port()

Signed-off-by: Yinghai Lu <yinghai.lu@sun.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Andi Kleen <ak@suse.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/serial/serial_core.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletion(-)

diff -puN drivers/serial/serial_core.c~serial-keep-the-dtr-setting-for-serial-console drivers/serial/serial_core.c
--- a/drivers/serial/serial_core.c~serial-keep-the-dtr-setting-for-serial-console
+++ a/drivers/serial/serial_core.c
@@ -2120,10 +2120,11 @@ uart_configure_port(struct uart_driver *
 
 		/*
 		 * Ensure that the modem control lines are de-activated.
+		 * keep the DTR setting that is set in uart_set_options()
 		 * We probably don't need a spinlock around this, but
 		 */
 		spin_lock_irqsave(&port->lock, flags);
-		port->ops->set_mctrl(port, 0);
+		port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR);
 		spin_unlock_irqrestore(&port->lock, flags);
 
 		/*
_