From 42f752b3fbcfee9c27e4f6f6216e60e130ba98c8 Mon Sep 17 00:00:00 2001 From: Dirk Behme 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 Signed-off-by: Greg Kroah-Hartman --- 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 952730ab9067..1c4f367b6fb6 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); -- 2.20.1