From 42f752b3fbcfee9c27e4f6f6216e60e130ba98c8 Mon Sep 17 00:00:00 2001
From: Dirk Behme <dirk.behme@de.bosch.com>
Date: Tue, 9 Dec 2014 18:11:28 +0900
Subject: [PATCH] serial: imx: use dma_is_txing to synchronize dma_tx_callback
and imx_dma_tx
To synchronize between dma_tx_callback() and imx_dma_tx() use the same
variable, dma_is_txing. This prevents any race between these two functions
and ensures that a new DMA can start only after the first has been
finished.
Before the new DMA can be set up, update the circular buffer logic, first.
Therefore, change dma_is_txing after that update, instead of before.
While doing this, in dma_tx_callback() extend the locking to dma_unmap_sg()
and the update of dma_is_txing.
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/serial/imx.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 952730ab90671..1c4f367b6fb6f 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -502,18 +502,20 @@ static void dma_tx_callback(void *data)
struct circ_buf *xmit = &sport->port.state->xmit;
unsigned long flags;
- dma_unmap_sg(sport->port.dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
+ spin_lock_irqsave(&sport->port.lock, flags);
- sport->dma_is_txing = 0;
+ dma_unmap_sg(sport->port.dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
/* update the stat */
- spin_lock_irqsave(&sport->port.lock, flags);
xmit->tail = (xmit->tail + sport->tx_bytes) & (UART_XMIT_SIZE - 1);
sport->port.icount.tx += sport->tx_bytes;
- spin_unlock_irqrestore(&sport->port.lock, flags);
dev_dbg(sport->port.dev, "we finish the TX DMA.\n");
+ sport->dma_is_txing = 0;
+
+ spin_unlock_irqrestore(&sport->port.lock, flags);
+
uart_write_wakeup(&sport->port);
if (waitqueue_active(&sport->dma_wait)) {
@@ -530,11 +532,9 @@ static void imx_dma_tx(struct imx_port *sport)
struct dma_async_tx_descriptor *desc;
struct dma_chan *chan = sport->dma_chan_tx;
struct device *dev = sport->port.dev;
- enum dma_status status;
int ret;
- status = dmaengine_tx_status(chan, (dma_cookie_t)0, NULL);
- if (DMA_IN_PROGRESS == status)
+ if (sport->dma_is_txing)
return;
sport->tx_bytes = uart_circ_chars_pending(xmit);
--
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