Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756226AbaLIJXs (ORCPT ); Tue, 9 Dec 2014 04:23:48 -0500 Received: from relay1.mentorg.com ([192.94.38.131]:62445 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755320AbaLIJLt (ORCPT ); Tue, 9 Dec 2014 04:11:49 -0500 From: Jiada Wang To: , , , CC: , , Subject: [PATCH v1 07/15] serial: imx: use dma_is_txing to synchronize dma_tx_callback and imx_dma_tx Date: Tue, 9 Dec 2014 18:11:28 +0900 Message-ID: <1418116296-12082-8-git-send-email-jiada_wang@mentor.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1418116296-12082-1-git-send-email-jiada_wang@mentor.com> References: <1418116296-12082-1-git-send-email-jiada_wang@mentor.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dirk Behme 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 --- 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 e53a058..3db6a5b 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); -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/