serial: imx: use locking to stop concurrent access of UCR1

Several places are accessing the UCR1 register without locking.
This probably will cause a race issue when another thread
is accessing the same register.
Add locking to preventing concurrent access of the UCR1 register.

Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index eb2210fa972e..c851247a27cb 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -731,6 +731,9 @@ static int start_rx_dma(struct imx_port *sport);
 static void imx_dma_rxint(struct imx_port *sport)
 {
         unsigned long temp;
+        unsigned long flags;
+
+        spin_lock_irqsave(&sport->port.lock, flags);
 
         temp = readl(sport->port.membase + USR2);
         if ((temp & USR2_RDR) && !sport->dma_is_rxing) {
@@ -744,6 +747,8 @@ static void imx_dma_rxint(struct imx_port *sport)
                 /* tell the DMA to receive the data. */
                 start_rx_dma(sport);
         }
+
+        spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 
 static irqreturn_t imx_int(int irq, void *dev_id)
@@ -873,6 +878,9 @@ static int imx_setup_ufcr(struct imx_port *sport, unsigned int mode)
 static void imx_rx_dma_done(struct imx_port *sport)
 {
         unsigned long temp;
+        unsigned long flags;
+
+        spin_lock_irqsave(&sport->port.lock, flags);
 
         /* Enable this interrupt when the RXFIFO is empty. */
         temp = readl(sport->port.membase + UCR1);
@@ -884,6 +892,8 @@ static void imx_rx_dma_done(struct imx_port *sport)
         /* Is the shutdown waiting for us? */
         if (waitqueue_active(&sport->dma_wait))
                 wake_up(&sport->dma_wait);
+
+        spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 
 /*
@@ -1194,9 +1204,11 @@ static void imx_shutdown(struct uart_port *port)
                         dmaengine_terminate_all(sport->dma_chan_tx);
                         dmaengine_terminate_all(sport->dma_chan_rx);
                 }
+                spin_lock_irqsave(&sport->port.lock, flags);
                 imx_stop_tx(port);
                 imx_stop_rx(port);
                 imx_disable_dma(sport);
+                spin_unlock_irqrestore(&sport->port.lock, flags);
                 imx_uart_dma_exit(sport);
         }