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

commit a377f9e906af4df9071ba8ddba60188cb4013d93 upstream.

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 <konstantin.shkolnyy@gmail.com>
Fixes: 39a66b8d22a3 ("[PATCH] USB: CP2101 Add support for flow control")
[johan: reword commit message ]
Signed-off-by: Johan Hovold <johan@kernel.org>
[johan: backport to 4.4 ]
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index 0093261ccc57dcf9b0a15b7841b511d987b0db82..d1582d83342c7b3448016ecb08c6f30250f8ddf2 100644 (file)
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -793,7 +793,7 @@ 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__);
                }