pch_uart: fix exclusive access issue

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/tty/serial/pch_uart.c

@@ -636,8 +636,7 @@ static void pch_dma_tx_complete(void *arg)
 	priv->tx_dma_use = 0;
 	priv->nent = 0;
 	kfree(priv->sg_tx_p);
-	if (uart_circ_chars_pending(xmit))
-		pch_uart_hal_enable_interrupt(priv, PCH_UART_HAL_TX_INT);
+	pch_uart_hal_enable_interrupt(priv, PCH_UART_HAL_TX_INT);
 }
 
 static int pop_tx(struct eg20t_port *priv, int size)
@@ -793,6 +792,14 @@ static unsigned int dma_handle_tx(struct eg20t_port *priv)
 		return 0;
 	}
 
+	if (priv->tx_dma_use) {
+		dev_dbg(priv->port.dev, "%s:Tx is not completed. (%lu)\n",
+			__func__, jiffies);
+		pch_uart_hal_disable_interrupt(priv, PCH_UART_HAL_TX_INT);
+		priv->tx_empty = 1;
+		return 0;
+	}
+
 	fifo_size = max(priv->fifo_size, 1);
 	tx_empty = 1;
 	if (pop_tx_x(priv, xmit->buf)) {