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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>
This commit is contained in:
Dirk Behme 2014-12-09 18:11:28 +09:00 committed by Greg Kroah-Hartman
parent 82e86ae941
commit 42f752b3fb
1 changed files with 9 additions and 9 deletions
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18
drivers/tty/serial/imx.c
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@ -502,18 +502,20 @@ static void dma_tx_callback(void *data)
struct circ_buf *xmit = &sport->port.state->xmit;
unsigned long flags;
spin_lock_irqsave(&sport->port.lock, flags);
dma_unmap_sg(sport->port.dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
/* update the stat */
xmit->tail = (xmit->tail + sport->tx_bytes) & (UART_XMIT_SIZE - 1);
sport->port.icount.tx += sport->tx_bytes;
dev_dbg(sport->port.dev, "we finish the TX DMA.\n");
sport->dma_is_txing = 0;
/* 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");
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);