tty: serial: samsung: Properly set flags in autoCTS mode

BugLink: https://bugs.launchpad.net/bugs/1818813

[ Upstream commit 31e93364 ]

Commit 391f93f2 ("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>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/tty/serial/samsung.c

@@ -1329,11 +1329,14 @@ 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;
 	}