From: Fugang Duan <fugang.duan@nxp.com>
Date: Thu, 25 Nov 2021 10:03:49 +0800
Subject: tty: serial: imx: disable UCR4_OREN in .stop_rx() instead of
 .shutdown()

Git-commit: 028e083832b06fdeeb290e1e57dc1f6702c4c215
Patch-mainline: v5.17-rc1
References: jsc#SLE-19033

The UCR4_OREN should be disabled before disabling the uart receiver in
.stop_rx() instead of in the .shutdown().

Otherwise, if we have the overrun error during the receiver disable
process, the overrun interrupt will keep trigging until we disable the
OREN interrupt in the .shutdown(), because the ORE status can only be
cleared when read the rx FIFO or reset the controller.  Although the
called time between the receiver disable and OREN disable in .shutdown()
is very short, there is still the risk of endless interrupt during this
short period of time. So here change to disable OREN before the receiver
been disabled in .stop_rx().

Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20211125020349.4980-1-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 drivers/tty/serial/imx.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index fb75e3e0d828..df8a0c8b8b29 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -486,18 +486,21 @@ static void imx_uart_stop_tx(struct uart_port *port)
 static void imx_uart_stop_rx(struct uart_port *port)
 {
 	struct imx_port *sport = (struct imx_port *)port;
-	u32 ucr1, ucr2;
+	u32 ucr1, ucr2, ucr4;
 
 	ucr1 = imx_uart_readl(sport, UCR1);
 	ucr2 = imx_uart_readl(sport, UCR2);
+	ucr4 = imx_uart_readl(sport, UCR4);
 
 	if (sport->dma_is_enabled) {
 		ucr1 &= ~(UCR1_RXDMAEN | UCR1_ATDMAEN);
 	} else {
 		ucr1 &= ~UCR1_RRDYEN;
 		ucr2 &= ~UCR2_ATEN;
+		ucr4 &= ~UCR4_OREN;
 	}
 	imx_uart_writel(sport, ucr1, UCR1);
+	imx_uart_writel(sport, ucr4, UCR4);
 
 	ucr2 &= ~UCR2_RXEN;
 	imx_uart_writel(sport, ucr2, UCR2);
@@ -1544,7 +1547,7 @@ static void imx_uart_shutdown(struct uart_port *port)
 	imx_uart_writel(sport, ucr1, UCR1);
 
 	ucr4 = imx_uart_readl(sport, UCR4);
-	ucr4 &= ~(UCR4_OREN | UCR4_TCEN);
+	ucr4 &= ~UCR4_TCEN;
 	imx_uart_writel(sport, ucr4, UCR4);
 
 	spin_unlock_irqrestore(&sport->port.lock, flags);
-- 
2.31.1