From: Johan Hovold <johan@kernel.org>
Date: Fri, 6 Jan 2017 18:15:12 +0000 (+0100)
Subject: USB: serial: ch341: fix modem-control and B0 handling
X-Git-Tag: firefly_0821_release~176^2~4^2~3^2~16
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=0cf23324af1c318c87fb2ea98be2443bc6a80835;p=firefly-linux-kernel-4.4.55.git

USB: serial: ch341: fix modem-control and B0 handling

commit 030ee7ae52a46a2be52ccc8242c4a330aba8d38e upstream.

The modem-control signals are managed by the tty-layer during open and
should not be asserted prematurely when set_termios is called from
driver open.

Also make sure that the signals are asserted only when changing speed
from B0.

Fixes: 664d5df92e88 ("USB: usb-serial ch341: support for DTR/RTS/CTS")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 8790679a0387..71133d96f97d 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -362,24 +362,24 @@ static void ch341_set_termios(struct tty_struct *tty,
 	baud_rate = tty_get_baud_rate(tty);
 
 	if (baud_rate) {
-		spin_lock_irqsave(&priv->lock, flags);
-		priv->line_control |= (CH341_BIT_DTR | CH341_BIT_RTS);
-		spin_unlock_irqrestore(&priv->lock, flags);
 		priv->baud_rate = baud_rate;
 		ch341_set_baudrate(port->serial->dev, priv);
-	} else {
-		spin_lock_irqsave(&priv->lock, flags);
-		priv->line_control &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
-		spin_unlock_irqrestore(&priv->lock, flags);
 	}
 
-	ch341_set_handshake(port->serial->dev, priv->line_control);
-
 	/* Unimplemented:
 	 * (cflag & CSIZE) : data bits [5, 8]
 	 * (cflag & PARENB) : parity {NONE, EVEN, ODD}
 	 * (cflag & CSTOPB) : stop bits [1, 2]
 	 */
+
+	spin_lock_irqsave(&priv->lock, flags);
+	if (C_BAUD(tty) == B0)
+		priv->line_control &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
+	else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
+		priv->line_control |= (CH341_BIT_DTR | CH341_BIT_RTS);
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	ch341_set_handshake(port->serial->dev, priv->line_control);
 }
 
 static void ch341_break_ctl(struct tty_struct *tty, int break_state)