[ARM] 4417/1: Serial: Fix AMBA drivers locking

The -rt patch triggered a lockdep warning in the amba serial drivers, which never
shows up on UP kernels. On SMP systems this would trigger as well.

Release the port lock before calling tty_flip_buffer_push() and reacquire it after
the call. This matches the code in the 8250 serial driver.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 4 insertions, 2 deletions

diff --git a/drivers/serial/amba-pl010.c b/drivers/serial/amba-pl010.c
index 1a9a24b82636..00d1255e4c12 100644
--- a/drivers/serial/amba-pl010.c
+++ b/drivers/serial/amba-pl010.c
@@ -167,8 +167,9 @@ static void pl010_rx_chars(struct uart_amba_port *uap)
         ignore_char:
                 status = readb(uap->port.membase + UART01x_FR);
         }
+        spin_unlock(&port->lock);
         tty_flip_buffer_push(tty);
-        return;
+        spin_lock(&port->lock);
 }
 
 static void pl010_tx_chars(struct uart_amba_port *uap)
diff --git a/drivers/serial/amba-pl011.c b/drivers/serial/amba-pl011.c
index 44639e71372a..954073c6ce3a 100644
--- a/drivers/serial/amba-pl011.c
+++ b/drivers/serial/amba-pl011.c
@@ -153,8 +153,9 @@ static void pl011_rx_chars(struct uart_amba_port *uap)
         ignore_char:
                 status = readw(uap->port.membase + UART01x_FR);
         }
+        spin_unlock(&uap->port.lock);
         tty_flip_buffer_push(tty);
-        return;
+        spin_lock(&uap->port.lock);
 }
 
 static void pl011_tx_chars(struct uart_amba_port *uap)