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

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>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/tty/serial/bfin_uart.c b/drivers/tty/serial/bfin_uart.c
index 26953bfa6922..5832fdef11e9 100644
--- 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);
         }