linux-kernel - [PATCH v2] serial: imx: protect Soft Reset of port with lock

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Date:	Mon, 13 Apr 2015 18:31:43 +0900
From:	Jiada Wang <jiada_wang@...tor.com>
To:	<gregkh@...uxfoundation.org>, <jslaby@...e.cz>
CC:	<linux-serial@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<jiada_wang@...tor.com>
Subject: [PATCH v2] serial: imx: protect Soft Reset of port with lock

Previously Soft Reset (clear of SRST bit in UCR2 register)
of UART in startup is not protected by lock, which may have race
with console_write, as console_write may occur at anytime even
when UART port is shutdown.

To avoid this race, protect Soft reset of UART port with spin_lock.

Signed-off-by: Jiada Wang <jiada_wang@...tor.com>
---
 drivers/tty/serial/imx.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index c8cfa06..38717c7 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1114,6 +1114,12 @@ static int imx_startup(struct uart_port *port)
 
 	writel(temp & ~UCR4_DREN, sport->port.membase + UCR4);
 
+	/* Can we enable the DMA support? */
+	if (is_imx6q_uart(sport) && !uart_console(port) &&
+	    !sport->dma_is_inited)
+		imx_uart_dma_init(sport);
+
+	spin_lock_irqsave(&sport->port.lock, flags);
 	/* Reset fifo's and state machines */
 	i = 100;
 
@@ -1124,13 +1130,6 @@ static int imx_startup(struct uart_port *port)
 	while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) && (--i > 0))
 		udelay(1);
 
-	/* Can we enable the DMA support? */
-	if (is_imx6q_uart(sport) && !uart_console(port) &&
-	    !sport->dma_is_inited)
-		imx_uart_dma_init(sport);
-
-	spin_lock_irqsave(&sport->port.lock, flags);
-
 	/*
 	 * Finally, clear and enable interrupts
 	 */
-- 
1.9.3

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