linux-kernel - [PATCH 1/9] serial: 8250

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Message-Id: <1365602312-25436-2-git-send-email-heikki.krogerus@linux.intel.com>
Date:	Wed, 10 Apr 2013 16:58:24 +0300
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: [PATCH 1/9] 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@...ux.intel.com>
---
 drivers/tty/serial/8250/8250_dma.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index b9f7fd2..ce2518d 100644
--- 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,
-- 
1.7.10.4

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