tty: serial: imx.c: Reset UART before activating interrupts

If the UART has been in use before this driver was loaded, IRQs might be
active and get fired as soon as we set the handler, which will crash
in the spin_lock_irqsave(&sport->port.lock, flags) because port.lock is
not initialized until the port is added at the end of probe.

Signed-off-by: David Jander <david@protonic.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 5b44d53f65b5d986590b048307521c563210cdaa..83b02d494723e3f732794d637d80f85ad9d0b6ca 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1098,10 +1098,23 @@ static void imx_disable_dma(struct imx_port *sport)
 /* half the RX buffer size */
 #define CTSTL 16
 
+static inline void imx_reset(struct imx_port *sport)
+{
+       int i = 100;
+       unsigned long temp;
+
+       temp = readl(sport->port.membase + UCR2);
+       temp &= ~UCR2_SRST;
+       writel(temp, sport->port.membase + UCR2);
+
+       while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) && (--i > 0))
+               udelay(1);
+}
+
 static int imx_startup(struct uart_port *port)
 {
        struct imx_port *sport = (struct imx_port *)port;
-       int retval, i;
+       int retval;
        unsigned long flags, temp;
 
        retval = clk_prepare_enable(sport->clk_per);
@@ -1133,14 +1146,7 @@ static int imx_startup(struct uart_port *port)
 
        spin_lock_irqsave(&sport->port.lock, flags);
        /* Reset fifo's and state machines */
-       i = 100;
-
-       temp = readl(sport->port.membase + UCR2);
-       temp &= ~UCR2_SRST;
-       writel(temp, sport->port.membase + UCR2);
-
-       while (!(readl(sport->port.membase + UCR2) & UCR2_SRST) && (--i > 0))
-               udelay(1);
+       imx_reset(sport);
 
        /*
         * Finally, clear and enable interrupts
@@ -1975,6 +1981,14 @@ static int serial_imx_probe(struct platform_device *pdev)
 
        clk_disable_unprepare(sport->clk_ipg);
 
+       /*
+        * Perform a complete reset of the UART device. Needed if we don't
+        * come straight out of reset.
+        */
+       writel(0, sport->port.membase + UCR2);
+       writel(0, sport->port.membase + UCR1);
+       imx_reset(sport);
+
        /*
         * Allocate the IRQ(s) i.MX1 has three interrupts whereas later
         * chips only have one interrupt.