[3.19.y-ckt stable] Patch "USB: serial: cp210x: fix hardware flow-control disable" has been added to the 3.19.y-ckt tree

Kamal Mostafa kamal at canonical.com
Wed Jul 6 21:00:29 UTC 2016

This is a note to let you know that I have just added a patch titled

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

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:


This patch is scheduled to be released in version 3.19.8-ckt23.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see



>From 3d22e3fec0e83f65f25707324067d532a52cb155 Mon Sep 17 00:00:00 2001
From: Konstantin Shkolnyy <konstantin.shkolnyy at gmail.com>
Date: Wed, 4 May 2016 16:56:52 -0500
Subject: 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 at gmail.com>
Fixes: 39a66b8d22a3 ("[PATCH] USB: CP2101 Add support for flow control")
[johan: reword commit message ]
Signed-off-by: Johan Hovold <johan at kernel.org>
[ kamal: backport to 4.2-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 drivers/usb/serial/cp210x.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index a2b43a6..c33dfff 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -784,7 +784,7 @@ 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__);


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