linux-kernel - [PATCH 1/4] mmc: dw_mmc: fix stop when fallen back to PIO

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Message-ID: <4E0AE23B.2010107@imgtec.com>
Date:	Wed, 29 Jun 2011 09:28:43 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	James Hogan <james.hogan@...tec.com>
CC:	Chris Ball <cjb@...top.org>, Will <will.newton@...tec.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/4] mmc: dw_mmc: fix stop when fallen back to PIO

There are several situations when dw_mci_submit_data_dma() decides to
fall back to PIO mode instead of using DMA, due to a short (to avoid
overhead) or "complex" (e.g. with unaligned buffers) transaction, even
though host->use_dma is set. However dw_mci_stop_dma() decides whether
to stop DMA or set the EVENT_XFER_COMPLETE event based on host->use_dma.
When falling back to PIO mode this results in data timeout errors
getting missed and the driver locking up.

Therefore add host->using_dma to indicate whether the current
transaction is using dma or not, and adjust dw_mci_stop_dma() to use
that instead.

Signed-off-by: James Hogan <james.hogan@...tec.com>
---
 drivers/mmc/host/dw_mmc.c  |    6 +++++-
 include/linux/mmc/dw_mmc.h |    2 ++
 2 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 10b6979..fcff3c0 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -287,7 +287,7 @@ static void send_stop_cmd(struct dw_mci *host, struct mmc_data *data)
 /* DMA interface functions */
 static void dw_mci_stop_dma(struct dw_mci *host)
 {
-	if (host->use_dma) {
+	if (host->using_dma) {
 		host->dma_ops->stop(host);
 		host->dma_ops->cleanup(host);
 	} else {
@@ -435,6 +435,8 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
 	unsigned int i, direction, sg_len;
 	u32 temp;
 
+	host->using_dma = 0;
+
 	/* If we don't have a channel, we can't do DMA */
 	if (!host->use_dma)
 		return -ENODEV;
@@ -454,6 +456,8 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
 			return -EINVAL;
 	}
 
+	host->using_dma = 1;
+
 	if (data->flags & MMC_DATA_READ)
 		direction = DMA_FROM_DEVICE;
 	else
diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
index f3f68ee..6b46819 100644
--- a/include/linux/mmc/dw_mmc.h
+++ b/include/linux/mmc/dw_mmc.h
@@ -48,6 +48,7 @@ struct mmc_data;
  * @data: The data currently being transferred, or NULL if no data
  *	transfer is in progress.
  * @use_dma: Whether DMA channel is initialized or not.
+ * @using_dma: Whether DMA is in use for the current transfer.
  * @sg_dma: Bus address of DMA buffer.
  * @sg_cpu: Virtual address of DMA buffer.
  * @dma_ops: Pointer to platform-specific DMA callbacks.
@@ -121,6 +122,7 @@ struct dw_mci {
 
 	/* DMA interface members*/
 	int			use_dma;
+	int			using_dma;
 
 	dma_addr_t		sg_dma;
 	void			*sg_cpu;
-- 
1.7.2.3


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