From 099506cbbc79c0bd52b19cb6b930f256dabc3950 Mon Sep 17 00:00:00 2001
From: "George G. Davis" <george_davis@mentor.com>
Date: Tue, 14 May 2019 23:29:34 -0400
Subject: [PATCH] serial: sh-sci: disable DMA for uart_console
Git-commit: 099506cbbc79c0bd52b19cb6b930f256dabc3950
Patch-mainline: v5.2-rc3
References: bsc#1051510

As noted in commit 84b40e3b57ee ("serial: 8250: omap: Disable DMA for
console UART"), UART console lines use low-level PIO only access functions
which will conflict with use of the line when DMA is enabled, e.g. when
the console line is also used for systemd messages. So disable DMA
support for UART console lines.

Reported-by: Michael Rodin <mrodin@de.adit-jv.com>
Link: https://patchwork.kernel.org/patch/10929511/
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: stable@vger.kernel.org
Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/tty/serial/sh-sci.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 3cd139752d3f..abc705716aa0 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1557,6 +1557,13 @@ static void sci_request_dma(struct uart_port *port)
 
 	dev_dbg(port->dev, "%s: port %d\n", __func__, port->line);
 
+	/*
+	 * DMA on console may interfere with Kernel log messages which use
+	 * plain putchar(). So, simply don't use it with a console.
+	 */
+	if (uart_console(port))
+		return;
+
 	if (!port->dev->of_node)
 		return;
 
-- 
2.16.4