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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Beomho Seo <beomho.seo@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.20 184/352] tty: serial: samsung: Properly set flags in autoCTS mode
Date:   Mon, 11 Feb 2019 15:16:51 +0100
Message-Id: <20190211141858.828673041@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 31e933645742ee6719d37573a27cce0761dcf92b ]

Commit 391f93f2ec9f ("serial: core: Rework hw-assited flow control support")
has changed the way the autoCTS mode is handled.

According to that change, serial drivers which enable H/W autoCTS mode must
set UPSTAT_AUTOCTS to prevent the serial core from inadvertently disabling
TX. This patch adds proper handling of UPSTAT_AUTOCTS flag.

Signed-off-by: Beomho Seo <beomho.seo@samsung.com>
[mszyprow: rephrased commit message]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/samsung.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index da1bd4bba8a9..2a49b6d876b8 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1365,11 +1365,14 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 	wr_regl(port, S3C2410_ULCON, ulcon);
 	wr_regl(port, S3C2410_UBRDIV, quot);
 
+	port->status &= ~UPSTAT_AUTOCTS;
+
 	umcon = rd_regl(port, S3C2410_UMCON);
 	if (termios->c_cflag & CRTSCTS) {
 		umcon |= S3C2410_UMCOM_AFC;
 		/* Disable RTS when RX FIFO contains 63 bytes */
 		umcon &= ~S3C2412_UMCON_AFC_8;
+		port->status = UPSTAT_AUTOCTS;
 	} else {
 		umcon &= ~S3C2410_UMCOM_AFC;
 	}
-- 
2.19.1