USB: serial: cp210x: fix hardware flow-control disable

[ Upstream commit a377f9e ]

A bug in the CRTSCTS handling caused RTS to alternate between

CRTSCTS=0 => "RTS is transmit active signal" and
CRTSCTS=1 => "RTS is used for receive flow control"

instead of

CRTSCTS=0 => "RTS is statically active" and
CRTSCTS=1 => "RTS is used for receive flow control"

This only happened after first having enabled CRTSCTS.

Signed-off-by: Konstantin Shkolnyy <[email protected]>
Fixes: 39a66b8 ("[PATCH] USB: CP2101 Add support for flow control")
Cc: stable <[email protected]>
[johan: reword commit message ]
Signed-off-by: Johan Hovold <[email protected]>

Signed-off-by: Sasha Levin <[email protected]>

Author: Konstantin Shkolnyy

drivers/usb/serial/cp210x.c

@@ -785,7 +785,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
 		} else {
 			modem_ctl[0] &= ~0x7B;
 			modem_ctl[0] |= 0x01;
-			modem_ctl[1] |= 0x40;
+			modem_ctl[1] = 0x40;
 			dev_dbg(dev, "%s - flow control = NONE\n", __func__);
 		}