linux-kernel - [PATCH 3.12 71/84] USB: serial: cp210x: fix hardware flow-control disable

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Date:   Mon, 17 Oct 2016 09:51:58 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>,
        Johan Hovold <johan@...nel.org>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 71/84] USB: serial: cp210x: fix hardware flow-control disable

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

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

===============

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: Jiri Slaby <jslaby@...e.cz>
---
 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 4063099f429a..17f737222b58 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -858,7 +858,7 @@ 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__);
 		}
 
-- 
2.10.1