serial: 8250_dma: TX cleanup

Removing one unneeded uart_write_wakeup(). There is no need
to start PIO transfer unless DMA fails, so this also changes
serial8250_tx_dma() to return 0 unless that is the case.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index b9f7fd2..ce2518d 100644 (file)
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -33,10 +33,8 @@ static void __dma_tx_complete(void *param)
        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(&p->port);
 
-       if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port)) {
+       if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port))
                serial8250_tx_dma(p);
-               uart_write_wakeup(&p->port);
-       }
 }
 
 static void __dma_rx_complete(void *param)
@@ -67,12 +65,11 @@ int serial8250_tx_dma(struct uart_8250_port *p)
        struct circ_buf                 *xmit = &p->port.state->xmit;
        struct dma_async_tx_descriptor  *desc;
 
-       if (dma->tx_running)
-               return -EBUSY;
+       if (uart_tx_stopped(&p->port) || dma->tx_running ||
+           uart_circ_empty(xmit))
+               return 0;
 
        dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
-       if (!dma->tx_size)
-               return -EINVAL;
 
        desc = dmaengine_prep_slave_single(dma->txchan,
                                           dma->tx_addr + xmit->tail,