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

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Message-id: <200708171641.56603.yinghai.lu@sun.com>
Date:	Fri, 17 Aug 2007 16:41:55 -0700
From:	Yinghai Lu <Yinghai.Lu@....COM>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <rmk@....linux.org.uk>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, Andi Kleen <ak@...e.de>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] serial: keep the DTR setting for serial console.

[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@....com>
Cc: Russell King <rmk@....linux.org.uk>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Andi Kleen <ak@...e.de>
Cc: Bjorn Helgaas <bjorn.helgaas@...com>

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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