tty: serial: imx: disable UCR4_OREN in .stop_rx() instead of .shutdown()

[ Upstream commit 028e083832 ]

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: Sasha Levin <sashal@kernel.org>

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);