[PATCH] Serial: Adjust serial locking

This patch changes the way serial ports are locked when getting modem
status.  This change is necessary because we will need to atomically
read the modem status and take action depending on the CTS status.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/serial/ip22zilog.c b/drivers/serial/ip22zilog.c
index 3ea46c069f6..ea5bf4d4daa 100644
--- a/drivers/serial/ip22zilog.c
+++ b/drivers/serial/ip22zilog.c
@@ -518,27 +518,28 @@ static irqreturn_t ip22zilog_interrupt(int irq, void *dev_id, struct pt_regs *re
 static __inline__ unsigned char ip22zilog_read_channel_status(struct uart_port *port)
 {
         struct zilog_channel *channel;
-        unsigned long flags;
         unsigned char status;
 
-        spin_lock_irqsave(&port->lock, flags);
-
         channel = ZILOG_CHANNEL_FROM_PORT(port);
         status = readb(&channel->control);
         ZSDELAY();
 
-        spin_unlock_irqrestore(&port->lock, flags);
-
         return status;
 }
 
 /* The port lock is not held.  */
 static unsigned int ip22zilog_tx_empty(struct uart_port *port)
 {
+        unsigned long flags;
         unsigned char status;
         unsigned int ret;
 
+        spin_lock_irqsave(&port->lock, flags);
+
         status = ip22zilog_read_channel_status(port);
+
+        spin_unlock_irqrestore(&port->lock, flags);
+
         if (status & Tx_BUF_EMP)
                 ret = TIOCSER_TEMT;
         else
@@ -547,7 +548,7 @@ static unsigned int ip22zilog_tx_empty(struct uart_port *port)
         return ret;
 }
 
-/* The port lock is not held.  */
+/* The port lock is held and interrupts are disabled.  */
 static unsigned int ip22zilog_get_mctrl(struct uart_port *port)
 {
         unsigned char status;