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serial: 8250_dma: TX optimisation 

Remove one useless wakeup, and do not use DMA with zero byte
transfers.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Heikki Krogerus 2013-01-16 14:08:14 +02:00 committed by Greg Kroah-Hartman
parent 6f3fe3b102
commit a3b0397fdf
1 changed files with 3 additions and 3 deletions
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6
drivers/tty/serial/8250/8250_dma.c
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@ -67,12 +67,12 @@ 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) {
uart_write_wakeup(&p->port);
if (dma->tx_running)
return -EBUSY;
}
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,