8250: fix autoconfig to work with serial console

The autoconfig prints messages while holding the
port's spinlock and that causes a deadlock when
using serial console.

Signed-off-by: Flavio Leitner <fbl@redhat.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c
index d4e0b07..932a216 100644 (file)
--- a/drivers/tty/serial/8250/8250.c
+++ b/drivers/tty/serial/8250/8250.c
@@ -1037,6 +1037,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
        unsigned char save_lcr, save_mcr;
        struct uart_port *port = &up->port;
        unsigned long flags;
+       unsigned int old_capabilities;
 
        if (!port->iobase && !port->mapbase && !port->membase)
                return;
@@ -1087,6 +1088,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
                        /*
                         * We failed; there's nothing here
                         */
+                       spin_unlock_irqrestore(&port->lock, flags);
                        DEBUG_AUTOCONF("IER test failed (%02x, %02x) ",
                                       scratch2, scratch3);
                        goto out;
@@ -1110,6 +1112,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
                status1 = serial_in(up, UART_MSR) & 0xF0;
                serial_out(up, UART_MCR, save_mcr);
                if (status1 != 0x90) {
+                       spin_unlock_irqrestore(&port->lock, flags);
                        DEBUG_AUTOCONF("LOOP test failed (%02x) ",
                                       status1);
                        goto out;
@@ -1132,8 +1135,6 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
        serial_out(up, UART_FCR, UART_FCR_ENABLE_FIFO);
        scratch = serial_in(up, UART_IIR) >> 6;
 
-       DEBUG_AUTOCONF("iir=%d ", scratch);
-
        switch (scratch) {
        case 0:
                autoconfig_8250(up);
@@ -1167,19 +1168,13 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
 
        serial_out(up, UART_LCR, save_lcr);
 
-       if (up->capabilities != uart_config[port->type].flags) {
-               printk(KERN_WARNING
-                      "ttyS%d: detected caps %08x should be %08x\n",
-                      serial_index(port), up->capabilities,
-                      uart_config[port->type].flags);
-       }
-
        port->fifosize = uart_config[up->port.type].fifo_size;
+       old_capabilities = up->capabilities; 
        up->capabilities = uart_config[port->type].flags;
        up->tx_loadsz = uart_config[port->type].tx_loadsz;
 
        if (port->type == PORT_UNKNOWN)
-               goto out;
+               goto out_lock;
 
        /*
         * Reset the UART.
@@ -1196,8 +1191,16 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
        else
                serial_out(up, UART_IER, 0);
 
- out:
+out_lock:
        spin_unlock_irqrestore(&port->lock, flags);
+       if (up->capabilities != old_capabilities) {
+               printk(KERN_WARNING
+                      "ttyS%d: detected caps %08x should be %08x\n",
+                      serial_index(port), old_capabilities,
+                      up->capabilities);
+       }
+out:
+       DEBUG_AUTOCONF("iir=%d ", scratch);
        DEBUG_AUTOCONF("type=%s\n", uart_config[port->type].name);
 }