linux-kernel - [PATCH 3.10 117/319] USB: serial: cp210x: fix hardware flow-control disable

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Message-Id: <1486322541-8206-18-git-send-email-w@1wt.eu>
Date:   Sun,  5 Feb 2017 20:18:59 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>,
        Johan Hovold <johan@...nel.org>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 117/319] USB: serial: cp210x: fix hardware flow-control disable

From: Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>

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@...il.com>
Fixes: 39a66b8d22a3 ("[PATCH] USB: CP2101 Add support for flow control")
[johan: reword commit message ]
Signed-off-by: Johan Hovold <johan@...nel.org>
[johan: backport to 4.4 ]
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 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 0093261..d1582d8 100644
--- 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__);
 		}
 
-- 
2.8.0.rc2.1.gbe9624a