[PATCH 4.4 85/93] USB: serial: cp210x: fix hardware flow-control disable

From: Greg Kroah-Hartman
Date: Thu Oct 06 2016 - 05:03:17 EST

4.4-stable review patch. If anyone has any objections, please let me know.


From: Konstantin Shkolnyy <konstantin.shkolnyy@xxxxxxxxx>

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@xxxxxxxxx>
Fixes: 39a66b8d22a3 ("[PATCH] USB: CP2101 Add support for flow control")
[johan: reword commit message ]
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
[johan: backport to 4.4 ]
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>


This is a backport of an upstream fix to v4.4, which should apply too
earlier stable trees as well.


drivers/usb/serial/cp210x.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -784,7 +784,7 @@ static void cp210x_set_termios(struct tt
} 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__);