linux-kernel - [PATCH v1 3/3] serial: 8250_port: Disable DMA operations for kernel console

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Message-Id: <20180515183409.78046-4-andriy.shevchenko@linux.intel.com>
Date:   Tue, 15 May 2018 21:34:09 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v1 3/3] serial: 8250_port: Disable DMA operations for kernel console

It will be too tricky and error prone to allow DMA operations on kernel
console.

Disable any kind of DMA operations in such case.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 drivers/tty/serial/8250/8250_port.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index db97222a1bf4..9a4696ea728b 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2371,7 +2371,10 @@ int serial8250_do_startup(struct uart_port *port)
 	 * Request DMA channels for both RX and TX.
 	 */
 	if (up->dma) {
-		retval = serial8250_request_dma(up);
+		if (uart_console(port))
+			retval = -ENXIO;
+		else
+			retval = serial8250_request_dma(up);
 		if (retval)
 			pr_warn_ratelimited("ttyS%d - failed to request DMA\n",
 					    serial_index(port));
-- 
2.17.0