From: Sergey Organov <sorganov@gmail.com>
Date: Fri, 26 Jul 2019 21:52:40 +0300
Subject: serial: imx: set_mctrl(): correctly restore autoRTS state
Git-commit: 197540dc8301a296e8ae7aa062f9f61f047eea05
Patch-mainline: v5.4-rc1
References: jsc#SLE-16106

imx_uart_set_mctrl() happened to set UCR2_CTSC bit whenever TIOCM_RTS
was set, no matter if RTS/CTS handshake is enabled or not. Now fixed by
turning handshake on only when CRTSCTS bit for the port is set.

Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Sergey Organov <sorganov@gmail.com>
Link: https://lore.kernel.org/r/1564167161-3972-3-git-send-email-sorganov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
 drivers/tty/serial/imx.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 32f36d86a960..059ba354d17e 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -974,10 +974,22 @@ static void imx_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
 	if (!(port->rs485.flags & SER_RS485_ENABLED)) {
 		u32 ucr2;
 
+		/*
+		 * Turn off autoRTS if RTS is lowered and restore autoRTS
+		 * setting if RTS is raised.
+		 */
 		ucr2 = imx_uart_readl(sport, UCR2);
 		ucr2 &= ~(UCR2_CTS | UCR2_CTSC);
-		if (mctrl & TIOCM_RTS)
-			ucr2 |= UCR2_CTS | UCR2_CTSC;
+		if (mctrl & TIOCM_RTS) {
+			ucr2 |= UCR2_CTS;
+			/*
+			 * UCR2_IRTS is unset if and only if the port is
+			 * configured for CRTSCTS, so we use inverted UCR2_IRTS
+			 * to get the state to restore to.
+			 */
+			if (!(ucr2 & UCR2_IRTS))
+				ucr2 |= UCR2_CTSC;
+		}
 		imx_uart_writel(sport, ucr2, UCR2);
 	}