From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Date: Wed, 16 Jan 2013 12:08:14 +0000 (+0200)
Subject: serial: 8250_dma: TX optimisation
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a3b0397fdf19b3c23f37012532482c787e01d4a0;p=linux-beck.git

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>
---

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 02333fc17f41..b9f7fd28112e 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -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,