[PATCH] serial: keep the DTR setting for serial console.

[Yinghai Lu]

[PATCH] serial: keep the DTR setting for serial console.

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@xxxxxxx>
Cc: Russell King <rmk@xxxxxxxxxxxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Cc: Bjorn Helgaas <bjorn.helgaas@xxxxxx>

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 030a606..70f1106 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -2117,10 +2117,11 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
 
 		/*
 		 * 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);
 
 		/*
-
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