From: Xinyu Chen <xinyu.chen@freescale.com>
Date: Fri, 2 Dec 2011 06:38:21 +0000 (+0800)
Subject: ENGR00163703 uart: console write routing is unsafe on SMP
X-Git-Tag: v3.0.35-fsl~1827
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=e4b3ccb5426bec41cd5ecf6ad3f655e9b8cb000f;p=karo-tx-linux.git

ENGR00163703 uart: console write routing is unsafe on SMP

The console feature's write routing is unsafe on SMP with
the startup/shutdown call. It happend to cause Android bootup
without shell runnable.

Actually on Android boot, there's 3 consumers of the console
* the kernel printk
* the init process using /dev/kmsg to call printk to show log
* shell, which open /dev/console and write with sys_write()

The shell goes into the normal uart open/write routing,
but the other two go into the console operations.
The open routing calls imx serial startup, which will write USR1/2
register without any lock and critical with imx_console_write call.

Here add spin_lock for startup/shutdown/console_write routing.
Remove the imx_setup_ufcr() call on startup when CONSOLE enabled,
as this will cause clock reinit, and output garbage.

Signed-off-by: Xinyu Chen <xinyu.chen@freescale.com>
---

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 0a8c6d0f963a..e484c82b6de9 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -902,7 +902,9 @@ static int imx_startup(struct uart_port *port)
 	unsigned long flags, temp;
 	struct tty_struct *tty;
 
+#ifndef CONFIG_SERIAL_CORE_CONSOLE
 	imx_setup_ufcr(sport, 0);
+#endif
 
 	/* disable the DREN bit (Data Ready interrupt enable) before
 	 * requesting IRQs
@@ -976,6 +978,7 @@ static int imx_startup(struct uart_port *port)
 		INIT_WORK(&sport->tsk_dma_rx, dma_rx_work);
 	}
 
+	spin_lock_irqsave(&sport->port.lock, flags);
 	/*
 	 * Finally, clear and enable interrupts
 	 */
@@ -1040,7 +1043,6 @@ static int imx_startup(struct uart_port *port)
 	/*
 	 * Enable modem status interrupts
 	 */
-	spin_lock_irqsave(&sport->port.lock,flags);
 	imx_enable_ms(&sport->port);
 	spin_unlock_irqrestore(&sport->port.lock,flags);
 
@@ -1074,10 +1076,13 @@ static void imx_shutdown(struct uart_port *port)
 {
 	struct imx_port *sport = (struct imx_port *)port;
 	unsigned long temp;
+	unsigned long flags;
 
+	spin_lock_irqsave(&sport->port.lock, flags);
 	temp = readl(sport->port.membase + UCR2);
 	temp &= ~(UCR2_TXEN);
 	writel(temp, sport->port.membase + UCR2);
+	spin_unlock_irqrestore(&sport->port.lock, flags);
 
 	if (USE_IRDA(sport)) {
 		struct imxuart_platform_data *pdata;
@@ -1106,12 +1111,15 @@ static void imx_shutdown(struct uart_port *port)
 	 * Disable all interrupts, port and break condition.
 	 */
 
+	spin_lock_irqsave(&sport->port.lock, flags);
 	temp = readl(sport->port.membase + UCR1);
 	temp &= ~(UCR1_TXMPTYEN | UCR1_RRDYEN | UCR1_RTSDEN | UCR1_UARTEN);
 	if (USE_IRDA(sport))
 		temp &= ~(UCR1_IREN);
 
 	writel(temp, sport->port.membase + UCR1);
+	spin_unlock_irqrestore(&sport->port.lock, flags);
+
 	if (sport->enable_dma)
 		imx_uart_dma_exit(sport);
 }
@@ -1272,6 +1280,7 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
 
 	if (UART_ENABLE_MS(&sport->port, termios->c_cflag))
 		imx_enable_ms(&sport->port);
+
 }
 
 static const char *imx_type(struct uart_port *port)
@@ -1392,7 +1401,9 @@ imx_console_write(struct console *co, const char *s, unsigned int count)
 {
 	struct imx_port *sport = imx_ports[co->index];
 	unsigned int old_ucr1, old_ucr2, ucr1;
+	unsigned long flags;
 
+	spin_lock_irqsave(&sport->port.lock, flags);
 	/*
 	 *	First, save UCR1/2 and then disable interrupts
 	 */
@@ -1418,6 +1429,7 @@ imx_console_write(struct console *co, const char *s, unsigned int count)
 
 	writel(old_ucr1, sport->port.membase + UCR1);
 	writel(old_ucr2, sport->port.membase + UCR2);
+	spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 
 /*