serial: bfin-uart: Don't access tty circular buffer in TX DMA interrupt after it...

When kernel reboot, tty circular buffer is reset before last TX DMA interrupt is called,
while the buffer tail is updated in TX DMA interrupt handler. So, don't update the buffer
tail if it is reset.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/bfin_uart.c b/drivers/tty/serial/bfin_uart.c
index 26953bf..5832fde 100644 (file)
--- a/drivers/tty/serial/bfin_uart.c
+++ b/drivers/tty/serial/bfin_uart.c
@@ -535,11 +535,13 @@ static irqreturn_t bfin_serial_dma_tx_int(int irq, void *dev_id)
                 *              when start a new tx.
                 */
                UART_CLEAR_IER(uart, ETBEI);
-               xmit->tail = (xmit->tail + uart->tx_count) & (UART_XMIT_SIZE - 1);
                uart->port.icount.tx += uart->tx_count;
+               if (!uart_circ_empty(xmit)) {
+                       xmit->tail = (xmit->tail + uart->tx_count) & (UART_XMIT_SIZE - 1);
 
-               if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-                       uart_write_wakeup(&uart->port);
+                       if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+                               uart_write_wakeup(&uart->port);
+               }
 
                bfin_serial_dma_tx_chars(uart);
        }