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 0a8c6d0f963afea319b4730f6bd3d68ec418d6c1..e484c82b6de99bea2fd6eb49284a8516327d81af 100644 (file)
--- 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);
 }
 
 /*