[PATCH v3 2/2] dmaengine: Add support for multiple descriptors for imx-dma.

[PATCH v3 2/2] dmaengine: Add support for multiple descriptors for imx-dma.

[Javier Martin]

dmaengine specifies the possibility that several descriptors
can be queued for transfer. It also indicates that tasklets
must be used for DMA callbacks.

Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
---
 Added comment explaining fall through in 'imxdma_xfer_desc'.

---
 drivers/dma/imx-dma.c |  332 ++++++++++++++++++++++++++++++++++++++-----------
 1 files changed, 258 insertions(+), 74 deletions(-)

diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
index 9aa6e85..c32103f 100644
--- a/drivers/dma/imx-dma.c
+++ b/drivers/dma/imx-dma.c
@@ -5,6 +5,7 @@
  * found on i.MX1/21/27
  *
  * Copyright 2010 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
+ * Copyright 2012 Javier Martin, Vista Silicon <javier.martin@vista-silicon.com>
  *
  * The code contained herein is licensed under the GNU General Public
  * License. You may obtain a copy of the GNU General Public License
@@ -13,6 +14,7 @@
  * http://www.opensource.org/licenses/gpl-license.html
  * http://www.gnu.org/copyleft/gpl.html
  */
+
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/types.h>
@@ -30,19 +32,52 @@
 #include <mach/dma-v1.h>
 #include <mach/hardware.h>
 
+#define IMXDMA_MAX_CHAN_DESCRIPTORS	16
+
+enum  imxdma_prep_type {
+	IMXDMA_DESC_MEMCPY,
+	IMXDMA_DESC_INTERLEAVED,
+	IMXDMA_DESC_SLAVE_SG,
+	IMXDMA_DESC_CYCLIC,
+};
+
+struct imxdma_desc {
+	struct list_head		node;
+	struct dma_async_tx_descriptor	desc;
+	enum dma_status			status;
+	dma_addr_t			src;
+	dma_addr_t			dest;
+	size_t				len;
+	unsigned int			dmamode;
+	enum imxdma_prep_type		type;
+	/* For memcpy and interleaved */
+	unsigned int			config_port;
+	unsigned int			config_mem;
+	/* For interleaved transfers */
+	unsigned int			x;
+	unsigned int			y;
+	unsigned int			w;
+	/* For slave sg and cyclic */
+	struct scatterlist		*sg;
+	unsigned int			sgcount;
+};
+
 struct imxdma_channel {
 	struct imxdma_engine		*imxdma;
 	unsigned int			channel;
 	unsigned int			imxdma_channel;
 
+	struct tasklet_struct		dma_tasklet;
+	struct list_head		ld_free;
+	struct list_head		ld_queue;
+	struct list_head		ld_active;
+	int				descs_allocated;
 	enum dma_slave_buswidth		word_size;
 	dma_addr_t			per_address;
 	u32				watermark_level;
 	struct dma_chan			chan;
 	spinlock_t			lock;
-	struct dma_async_tx_descriptor	desc;
 	dma_cookie_t			last_completed;
-	enum dma_status			status;
 	int				dma_request;
 	struct scatterlist		*sg_list;
 };
@@ -61,27 +96,31 @@ static struct imxdma_channel *to_imxdma_chan(struct dma_chan *chan)
 	return container_of(chan, struct imxdma_channel, chan);
 }
 
-static void imxdma_handle(struct imxdma_channel *imxdmac)
+static inline bool imxdma_chan_is_doing_cyclic(struct imxdma_channel *imxdmac)
 {
-	if (imxdmac->desc.callback)
-		imxdmac->desc.callback(imxdmac->desc.callback_param);
-	imxdmac->last_completed = imxdmac->desc.cookie;
+	struct imxdma_desc *desc;
+
+	if (!list_empty(&imxdmac->ld_active)) {
+		desc = list_first_entry(&imxdmac->ld_active, struct imxdma_desc,
+					node);
+		if (desc->type == IMXDMA_DESC_CYCLIC)
+			return true;
+	}
+	return false;
 }
 
 static void imxdma_irq_handler(int channel, void *data)
 {
 	struct imxdma_channel *imxdmac = data;
 
-	imxdmac->status = DMA_SUCCESS;
-	imxdma_handle(imxdmac);
+	tasklet_schedule(&imxdmac->dma_tasklet);
 }
 
 static void imxdma_err_handler(int channel, void *data, int error)
 {
 	struct imxdma_channel *imxdmac = data;
 
-	imxdmac->status = DMA_ERROR;
-	imxdma_handle(imxdmac);
+	tasklet_schedule(&imxdmac->dma_tasklet);
 }
 
 static void imxdma_progression(int channel, void *data,
@@ -89,8 +128,88 @@ static void imxdma_progression(int channel, void *data,
 {
 	struct imxdma_channel *imxdmac = data;
 
-	imxdmac->status = DMA_SUCCESS;
-	imxdma_handle(imxdmac);
+	tasklet_schedule(&imxdmac->dma_tasklet);
+}
+
+static int imxdma_xfer_desc(struct imxdma_desc *d)
+{
+	struct imxdma_channel *imxdmac = to_imxdma_chan(d->desc.chan);
+	int ret;
+
+	/* Configure and enable */
+	switch (d->type) {
+	case IMXDMA_DESC_MEMCPY:
+		ret = imx_dma_config_channel(imxdmac->imxdma_channel,
+					  d->config_port, d->config_mem, 0, 0);
+		if (ret < 0)
+			return ret;
+		ret = imx_dma_setup_single(imxdmac->imxdma_channel, d->src,
+					   d->len, d->dest, d->dmamode);
+		if (ret < 0)
+			return ret;
+		break;
+	case IMXDMA_DESC_CYCLIC:
+		ret = imx_dma_setup_progression_handler(imxdmac->imxdma_channel,
+							imxdma_progression);
+		if (ret < 0)
+			return ret;
+		/*
+		 * We fall through here since cyclic transfer is the same as
+		 * slave_sg adding a progression handler and a specific sg
+		 * configuration which is done in 'imxdma_prep_dma_cyclic'.
+		 */
+	case IMXDMA_DESC_SLAVE_SG:
+		if (d->dmamode == DMA_MODE_READ)
+			ret = imx_dma_setup_sg(imxdmac->imxdma_channel, d->sg,
+				       d->sgcount, d->len, d->src, d->dmamode);
+		else
+			ret = imx_dma_setup_sg(imxdmac->imxdma_channel, d->sg,
+				      d->sgcount, d->len, d->dest, d->dmamode);
+		if (ret < 0)
+			return ret;
+		break;
+	default:
+		return -EINVAL;
+	}
+	imx_dma_enable(imxdmac->imxdma_channel);
+	return 0;
+}
+
+static void imxdma_tasklet(unsigned long data)
+{
+	struct imxdma_channel *imxdmac = (void *)data;
+	struct imxdma_engine *imxdma = imxdmac->imxdma;
+	struct imxdma_desc *desc;
+
+	spin_lock(&imxdmac->lock);
+
+	if (list_empty(&imxdmac->ld_active)) {
+		/* Someone might have called terminate all */
+		goto out;
+	}
+	desc = list_first_entry(&imxdmac->ld_active, struct imxdma_desc, node);
+
+	if (desc->desc.callback)
+		desc->desc.callback(desc->desc.callback_param);
+
+	imxdmac->last_completed = desc->desc.cookie;
+
+	/* If we are dealing with a cyclic descriptor keep it on ld_active */
+	if (imxdma_chan_is_doing_cyclic(imxdmac))
+		goto out;
+
+	list_move_tail(imxdmac->ld_active.next, &imxdmac->ld_free);
+
+	if (!list_empty(&imxdmac->ld_queue)) {
+		desc = list_first_entry(&imxdmac->ld_queue, struct imxdma_desc,
+					node);
+		list_move_tail(imxdmac->ld_queue.next, &imxdmac->ld_active);
+		if (imxdma_xfer_desc(desc) < 0)
+			dev_warn(imxdma->dev, "%s: channel: %d couldn't xfer desc\n",
+				 __func__, imxdmac->channel);
+	}
+out:
+	spin_unlock(&imxdmac->lock);
 }
 
 static int imxdma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
@@ -99,12 +218,17 @@ static int imxdma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
 	struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
 	struct dma_slave_config *dmaengine_cfg = (void *)arg;
 	int ret;
+	unsigned long flags;
 	unsigned int mode = 0;
 
 	switch (cmd) {
 	case DMA_TERMINATE_ALL:
-		imxdmac->status = DMA_ERROR;
 		imx_dma_disable(imxdmac->imxdma_channel);
+
+		spin_lock_irqsave(&imxdmac->lock, flags);
+		list_splice_tail_init(&imxdmac->ld_active, &imxdmac->ld_free);
+		list_splice_tail_init(&imxdmac->ld_queue, &imxdmac->ld_free);
+		spin_unlock_irqrestore(&imxdmac->lock, flags);
 		return 0;
 	case DMA_SLAVE_CONFIG:
 		if (dmaengine_cfg->direction == DMA_DEV_TO_MEM) {
@@ -155,11 +279,14 @@ static enum dma_status imxdma_tx_status(struct dma_chan *chan,
 	struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
 	dma_cookie_t last_used;
 	enum dma_status ret;
+	unsigned long flags;
 
+	spin_lock_irqsave(&imxdmac->lock, flags);
 	last_used = chan->cookie;
 
 	ret = dma_async_is_complete(cookie, imxdmac->last_completed, last_used);
 	dma_set_tx_state(txstate, imxdmac->last_completed, last_used, 0);
+	spin_unlock_irqrestore(&imxdmac->lock, flags);
 
 	return ret;
 }
@@ -172,7 +299,6 @@ static dma_cookie_t imxdma_assign_cookie(struct imxdma_channel *imxdma)
 		cookie = 1;
 
 	imxdma->chan.cookie = cookie;
-	imxdma->desc.cookie = cookie;
 
 	return cookie;
 }
@@ -181,12 +307,15 @@ static dma_cookie_t imxdma_tx_submit(struct dma_async_tx_descriptor *tx)
 {
 	struct imxdma_channel *imxdmac = to_imxdma_chan(tx->chan);
 	dma_cookie_t cookie;
+	unsigned long flags;
 
-	spin_lock_irq(&imxdmac->lock);
+	spin_lock_irqsave(&imxdmac->lock, flags);
 
+	list_move_tail(imxdmac->ld_free.next, &imxdmac->ld_queue);
 	cookie = imxdma_assign_cookie(imxdmac);
+	tx->cookie = cookie;
 
-	spin_unlock_irq(&imxdmac->lock);
+	spin_unlock_irqrestore(&imxdmac->lock, flags);
 
 	return cookie;
 }
@@ -199,21 +328,48 @@ static int imxdma_alloc_chan_resources(struct dma_chan *chan)
 	if (data != NULL)
 		imxdmac->dma_request = data->dma_request;
 
-	dma_async_tx_descriptor_init(&imxdmac->desc, chan);
-	imxdmac->desc.tx_submit = imxdma_tx_submit;
-	/* txd.flags will be overwritten in prep funcs */
-	imxdmac->desc.flags = DMA_CTRL_ACK;
+	while (imxdmac->descs_allocated < IMXDMA_MAX_CHAN_DESCRIPTORS) {
+		struct imxdma_desc *desc;
 
-	imxdmac->status = DMA_SUCCESS;
+		desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+		if (!desc)
+			break;
+		__memzero(&desc->desc, sizeof(struct dma_async_tx_descriptor));
+		dma_async_tx_descriptor_init(&desc->desc, chan);
+		desc->desc.tx_submit = imxdma_tx_submit;
+		/* txd.flags will be overwritten in prep funcs */
+		desc->desc.flags = DMA_CTRL_ACK;
+		desc->status = DMA_SUCCESS;
+
+		list_add_tail(&desc->node, &imxdmac->ld_free);
+		imxdmac->descs_allocated++;
+	}
 
-	return 0;
+	if (!imxdmac->descs_allocated)
+		return -ENOMEM;
+
+	return imxdmac->descs_allocated;
 }
 
 static void imxdma_free_chan_resources(struct dma_chan *chan)
 {
 	struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
+	struct imxdma_desc *desc, *_desc;
+	unsigned long flags;
+
+	spin_lock_irqsave(&imxdmac->lock, flags);
 
 	imx_dma_disable(imxdmac->imxdma_channel);
+	list_splice_tail_init(&imxdmac->ld_active, &imxdmac->ld_free);
+	list_splice_tail_init(&imxdmac->ld_queue, &imxdmac->ld_free);
+
+	spin_unlock_irqrestore(&imxdmac->lock, flags);
+
+	list_for_each_entry_safe(desc, _desc, &imxdmac->ld_free, node) {
+		kfree(desc);
+		imxdmac->descs_allocated--;
+	}
+	INIT_LIST_HEAD(&imxdmac->ld_free);
 
 	if (imxdmac->sg_list) {
 		kfree(imxdmac->sg_list);
@@ -228,23 +384,19 @@ static struct dma_async_tx_descriptor *imxdma_prep_slave_sg(
 {
 	struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
 	struct scatterlist *sg;
-	int i, ret, dma_length = 0;
-	unsigned int dmamode;
+	int i, dma_length = 0;
+	struct imxdma_desc *desc;
 
-	if (imxdmac->status == DMA_IN_PROGRESS)
+	if (list_empty(&imxdmac->ld_free) ||
+	    imxdma_chan_is_doing_cyclic(imxdmac))
 		return NULL;
 
-	imxdmac->status = DMA_IN_PROGRESS;
+	desc = list_first_entry(&imxdmac->ld_free, struct imxdma_desc, node);
 
 	for_each_sg(sgl, sg, sg_len, i) {
 		dma_length += sg->length;
 	}
 
-	if (direction == DMA_DEV_TO_MEM)
-		dmamode = DMA_MODE_READ;
-	else
-		dmamode = DMA_MODE_WRITE;
-
 	switch (imxdmac->word_size) {
 	case DMA_SLAVE_BUSWIDTH_4_BYTES:
 		if (sgl->length & 3 || sgl->dma_address & 3)
@@ -260,12 +412,21 @@ static struct dma_async_tx_descriptor *imxdma_prep_slave_sg(
 		return NULL;
 	}
 
-	ret = imx_dma_setup_sg(imxdmac->imxdma_channel, sgl, sg_len,
-		 dma_length, imxdmac->per_address, dmamode);
-	if (ret)
-		return NULL;
+	desc->type = IMXDMA_DESC_SLAVE_SG;
+	desc->sg = sgl;
+	desc->sgcount = sg_len;
+	desc->len = dma_length;
+	if (direction == DMA_DEV_TO_MEM) {
+		desc->dmamode = DMA_MODE_READ;
+		desc->src = imxdmac->per_address;
+	} else {
+		desc->dmamode = DMA_MODE_WRITE;
+		desc->dest = imxdmac->per_address;
+	}
+	desc->desc.callback = NULL;
+	desc->desc.callback_param = NULL;
 
-	return &imxdmac->desc;
+	return &desc->desc;
 }
 
 static struct dma_async_tx_descriptor *imxdma_prep_dma_cyclic(
@@ -274,23 +435,18 @@ static struct dma_async_tx_descriptor *imxdma_prep_dma_cyclic(
 {
 	struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
 	struct imxdma_engine *imxdma = imxdmac->imxdma;
-	int i, ret;
+	struct imxdma_desc *desc;
+	int i;
 	unsigned int periods = buf_len / period_len;
-	unsigned int dmamode;
 
 	dev_dbg(imxdma->dev, "%s channel: %d buf_len=%d period_len=%d\n",
 			__func__, imxdmac->channel, buf_len, period_len);
 
-	if (imxdmac->status == DMA_IN_PROGRESS)
+	if (list_empty(&imxdmac->ld_free) ||
+	    imxdma_chan_is_doing_cyclic(imxdmac))
 		return NULL;
-	imxdmac->status = DMA_IN_PROGRESS;
 
-	ret = imx_dma_setup_progression_handler(imxdmac->imxdma_channel,
-			imxdma_progression);
-	if (ret) {
-		dev_err(imxdma->dev, "Failed to setup the DMA handler\n");
-		return NULL;
-	}
+	desc = list_first_entry(&imxdmac->ld_free, struct imxdma_desc, node);
 
 	if (imxdmac->sg_list)
 		kfree(imxdmac->sg_list);
@@ -316,17 +472,21 @@ static struct dma_async_tx_descriptor *imxdma_prep_dma_cyclic(
 	imxdmac->sg_list[periods].page_link =
 		((unsigned long)imxdmac->sg_list | 0x01) & ~0x02;
 
-	if (direction == DMA_DEV_TO_MEM)
-		dmamode = DMA_MODE_READ;
-	else
-		dmamode = DMA_MODE_WRITE;
-
-	ret = imx_dma_setup_sg(imxdmac->imxdma_channel, imxdmac->sg_list, periods,
-		 IMX_DMA_LENGTH_LOOP, imxdmac->per_address, dmamode);
-	if (ret)
-		return NULL;
+	desc->type = IMXDMA_DESC_CYCLIC;
+	desc->sg = imxdmac->sg_list;
+	desc->sgcount = periods;
+	desc->len = IMX_DMA_LENGTH_LOOP;
+	if (direction == DMA_DEV_TO_MEM) {
+		desc->dmamode = DMA_MODE_READ;
+		desc->src = imxdmac->per_address;
+	} else {
+		desc->dmamode = DMA_MODE_WRITE;
+		desc->dest = imxdmac->per_address;
+	}
+	desc->desc.callback = NULL;
+	desc->desc.callback_param = NULL;
 
-	return &imxdmac->desc;
+	return &desc->desc;
 }
 
 static struct dma_async_tx_descriptor *imxdma_prep_dma_memcpy(
@@ -335,36 +495,53 @@ static struct dma_async_tx_descriptor *imxdma_prep_dma_memcpy(
 {
 	struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
 	struct imxdma_engine *imxdma = imxdmac->imxdma;
-	int ret;
+	struct imxdma_desc *desc;
 
 	dev_dbg(imxdma->dev, "%s channel: %d src=0x%x dst=0x%x len=%d\n",
 			__func__, imxdmac->channel, src, dest, len);
 
-	if (imxdmac->status == DMA_IN_PROGRESS)
+	if (list_empty(&imxdmac->ld_free) ||
+	    imxdma_chan_is_doing_cyclic(imxdmac))
 		return NULL;
-	imxdmac->status = DMA_IN_PROGRESS;
 
-	ret = imx_dma_config_channel(imxdmac->imxdma_channel,
-			       IMX_DMA_MEMSIZE_32 | IMX_DMA_TYPE_LINEAR,
-			       IMX_DMA_MEMSIZE_32 | IMX_DMA_TYPE_LINEAR,
-			       0, 0);
-	if (ret)
-		return NULL;
+	desc = list_first_entry(&imxdmac->ld_free, struct imxdma_desc, node);
 
-	ret = imx_dma_setup_single(imxdmac->imxdma_channel, src, len,
-				   dest, DMA_MODE_WRITE);
-	if (ret)
-		return NULL;
+	desc->type = IMXDMA_DESC_MEMCPY;
+	desc->src = src;
+	desc->dest = dest;
+	desc->len = len;
+	desc->dmamode = DMA_MODE_WRITE;
+	desc->config_port = IMX_DMA_MEMSIZE_32 | IMX_DMA_TYPE_LINEAR;
+	desc->config_mem = IMX_DMA_MEMSIZE_32 | IMX_DMA_TYPE_LINEAR;
+	desc->desc.callback = NULL;
+	desc->desc.callback_param = NULL;
 
-	return &imxdmac->desc;
+	return &desc->desc;
 }
 
 static void imxdma_issue_pending(struct dma_chan *chan)
 {
 	struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
-
-	if (imxdmac->status == DMA_IN_PROGRESS)
-		imx_dma_enable(imxdmac->imxdma_channel);
+	struct imxdma_engine *imxdma = imxdmac->imxdma;
+	struct imxdma_desc *desc;
+	unsigned long flags;
+
+	spin_lock_irqsave(&imxdmac->lock, flags);
+	if (list_empty(&imxdmac->ld_active) &&
+	    !list_empty(&imxdmac->ld_queue)) {
+		desc = list_first_entry(&imxdmac->ld_queue,
+					struct imxdma_desc, node);
+
+		if (imxdma_xfer_desc(desc) < 0) {
+			dev_warn(imxdma->dev,
+				 "%s: channel: %d couldn't issue DMA xfer\n",
+				 __func__, imxdmac->channel);
+		} else {
+			list_move_tail(imxdmac->ld_queue.next,
+				       &imxdmac->ld_active);
+		}
+	}
+	spin_unlock_irqrestore(&imxdmac->lock, flags);
 }
 
 static int __init imxdma_probe(struct platform_device *pdev)
@@ -399,11 +576,18 @@ static int __init imxdma_probe(struct platform_device *pdev)
 		imxdmac->imxdma = imxdma;
 		spin_lock_init(&imxdmac->lock);
 
+		INIT_LIST_HEAD(&imxdmac->ld_queue);
+		INIT_LIST_HEAD(&imxdmac->ld_free);
+		INIT_LIST_HEAD(&imxdmac->ld_active);
+
+		tasklet_init(&imxdmac->dma_tasklet, imxdma_tasklet,
+			     (unsigned long)imxdmac);
 		imxdmac->chan.device = &imxdma->dma_device;
 		imxdmac->channel = i;
 
 		/* Add the channel to the DMAC list */
-		list_add_tail(&imxdmac->chan.device_node, &imxdma->dma_device.channels);
+		list_add_tail(&imxdmac->chan.device_node,
+			      &imxdma->dma_device.channels);
 	}
 
 	imxdma->dev = &pdev->dev;
-- 
1.7.0.4

[PATCH v3 2/2] dmaengine: Add support for multiple descriptors for imx-dma.

[Vinod Koul]

On Fri, 2012-03-02 at 09:28 +0100, Javier Martin wrote:
> dmaengine specifies the possibility that several descriptors
> can be queued for transfer. It also indicates that tasklets
> must be used for DMA callbacks.
> 
> Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
> Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
> ---
Applied this and 1/2 or previous one

-- 
~Vinod

[BUG ?] ARM: imx27: dmaengine: imx-dma: SD-Card: copy hangs forever

[Vinod Koul]

On Sun, Jun 09, 2013 at 11:39:06PM +0200, Christoph Fritz wrote:
> Hi,
Thanks for the bug report, we are discussing this issue in [1]

--
~Vinod

[1]: http://www.spinics.net/lists/arm-kernel/msg249815.html
> 
>  an imx27-board (pca100) hits a DEADLOCK with current stable Kernel
> 3.4.47 while adding a SD-Card:
> 
> =================================
> [ INFO: inconsistent lock state ]
> 3.4.47-00059-ga5527fe #213 Not tainted
> ---------------------------------
> inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
> swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
>  (&(&imxdma->lock)->rlock){?.-...}, at: [<c01b9d18>] imxdma_tasklet+0x1c/0x138
> {IN-HARDIRQ-W} state was registered at:
>   [<c004e96c>] __lock_acquire+0x97c/0x1900
>   [<c004fd98>] lock_acquire+0x64/0x78
>   [<c03bcd18>] _raw_spin_lock+0x40/0x50
>   [<c01ba018>] dma_irq_handler+0xc8/0x358
>   [<c005c750>] handle_irq_event_percpu+0x50/0x1c8
>   [<c005c904>] handle_irq_event+0x3c/0x5c
>   [<c005ea5c>] handle_level_irq+0x8c/0xd8
>   [<c005c0c8>] generic_handle_irq+0x34/0x48
>   [<c000975c>] handle_IRQ+0x30/0x84
>   [<c00086e8>] avic_handle_irq+0x2c/0x4c
>   [<c03bd924>] __irq_svc+0x44/0x74
>   [<c00098c4>] default_idle+0x40/0x48
>   [<c0009a60>] cpu_idle+0x6c/0xe8
>   [<c0525700>] start_kernel+0x264/0x2a4
> irq event stamp: 20208
> hardirqs last  enabled at (20208): [<c001c0fc>] tasklet_action+0x30/0xe0
> hardirqs last disabled at (20207): [<c001c0e4>] tasklet_action+0x18/0xe0
> softirqs last  enabled at (20202): [<c001bc8c>] irq_enter+0x6c/0x70
> softirqs last disabled at (20203): [<c001bd2c>] irq_exit+0x9c/0xa8
> 
> other info that might help us debug this:
>  Possible unsafe locking scenario:
> 
>        CPU0
>        ----
>   lock(&(&imxdma->lock)->rlock);
>   <Interrupt>
>     lock(&(&imxdma->lock)->rlock);
> 
>  *** DEADLOCK ***
> 
> no locks held by swapper/0.
> 
> stack backtrace:
> [<c000d428>] (unwind_backtrace+0x0/0xf0) from [<c03b7724>] (print_usage_bug.part.25+0x208/0x268)
> [<c03b7724>] (print_usage_bug.part.25+0x208/0x268) from [<c004decc>] (mark_lock+0x4fc/0x620)
> [<c004decc>] (mark_lock+0x4fc/0x620) from [<c004e870>] (__lock_acquire+0x880/0x1900)
> [<c004e870>] (__lock_acquire+0x880/0x1900) from [<c004fd98>] (lock_acquire+0x64/0x78)
> [<c004fd98>] (lock_acquire+0x64/0x78) from [<c03bcd18>] (_raw_spin_lock+0x40/0x50)
> [<c03bcd18>] (_raw_spin_lock+0x40/0x50) from [<c01b9d18>] (imxdma_tasklet+0x1c/0x138)
> [<c01b9d18>] (imxdma_tasklet+0x1c/0x138) from [<c001c144>] (tasklet_action+0x78/0xe0)
> [<c001c144>] (tasklet_action+0x78/0xe0) from [<c001b76c>] (__do_softirq+0xc8/0x17c)
> [<c001b76c>] (__do_softirq+0xc8/0x17c) from [<c001bd2c>] (irq_exit+0x9c/0xa8)
> [<c001bd2c>] (irq_exit+0x9c/0xa8) from [<c0009760>] (handle_IRQ+0x34/0x84)
> [<c0009760>] (handle_IRQ+0x34/0x84) from [<c00086e8>] (avic_handle_irq+0x2c/0x4c)
> [<c00086e8>] (avic_handle_irq+0x2c/0x4c) from [<c03bd924>] (__irq_svc+0x44/0x74)
> Exception stack(0xc0549f60 to 0xc0549fa8)
> 9f60: 00000001 00000001 00000000 20000013 c0548000 c058dae8 c0554118 c0548000
> 9f80: c0b96500 41069264 a053ff1c 00000000 600000d3 c0549fa8 c0050664 c00098c4
> 9fa0: 20000013 ffffffff
> [<c03bd924>] (__irq_svc+0x44/0x74) from [<c00098c4>] (default_idle+0x40/0x48)
> [<c00098c4>] (default_idle+0x40/0x48) from [<c0009a60>] (cpu_idle+0x6c/0xe8)
> [<c0009a60>] (cpu_idle+0x6c/0xe8) from [<c0525700>] (start_kernel+0x264/0x2a4)
> 
> 
> This is also curious and may be related:
> 
> When CONFIG_IMX_DMA is disabled, copying a file to SD-Card is relatively
> fast:
>     $ dd if=/dev/zero of=/mnt/test count=102400  bs=1K
>     102400+0 records in
>     102400+0 records out
>     104857600 bytes (105 MB) copied, 33.573 s, 3.1 MB/s
> 
> When CONFIG_IMX_DMA is enabled, copying a file to SD-Card is
> very slow for small files and takes forever for files roughly bigger
> than 1.0MB:
> 
>     $ dd if=/dev/zero of=/mnt/test count=100000  bs=10
>     100000+0 records in
>     100000+0 records out
>     1000000 bytes (1.0 MB) copied, 18.3172 s, 54.6 kB/s
> 
>     $ dd if=/dev/zero of=/mnt/performance_test.102400KB count=100000  bs=20
> 
> INFO: task mmcqd/0:592 blocked for more than 30 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> mmcqd/0         D c03bbf14     0   592      2 0x00000000
> [<c03bbf14>] (__schedule+0x220/0x590) from [<c03ba11c>] (schedule_timeout+0x154/0x1bc)
> [<c03ba11c>] (schedule_timeout+0x154/0x1bc) from [<c03bbbac>] (wait_for_common+0xac/0x150)
> [<c03bbbac>] (wait_for_common+0xac/0x150) from [<c0285504>] (mmc_wait_for_req_done+0x1c/0x74)
> [<c0285504>] (mmc_wait_for_req_done+0x1c/0x74) from [<c028612c>] (mmc_start_req+0x54/0x118)
> [<c028612c>] (mmc_start_req+0x54/0x118) from [<c02911d0>] (mmc_blk_issue_rw_rq+0x64/0x380)
> [<c02911d0>] (mmc_blk_issue_rw_rq+0x64/0x380) from [<c029169c>] (mmc_blk_issue_rq+0x1b0/0x484)
> [<c029169c>] (mmc_blk_issue_rq+0x1b0/0x484) from [<c029293c>] (mmc_queue_thread+0x58/0xf4)
> [<c029293c>] (mmc_queue_thread+0x58/0xf4) from [<c0032acc>] (kthread+0x84/0x90)
> [<c0032acc>] (kthread+0x84/0x90) from [<c0009844>] (kernel_thread_exit+0x0/0x8)
> no locks held by mmcqd/0/592.
> INFO: task kjournald:595 blocked for more than 30 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> kjournald       D c03bbf14     0   595      2 0x00000000
> [<c03bbf14>] (__schedule+0x220/0x590) from [<c03bc3b0>] (io_schedule+0x60/0x94)
> [<c03bc3b0>] (io_schedule+0x60/0x94) from [<c00c54a0>] (sleep_on_buffer+0x8/0x10)
> [<c00c54a0>] (sleep_on_buffer+0x8/0x10) from [<c03ba24c>] (__wait_on_bit+0x74/0xb8)
> [<c03ba24c>] (__wait_on_bit+0x74/0xb8) from [<c03ba2f4>] (out_of_line_wait_on_bit+0x64/0x70)
> [<c03ba2f4>] (out_of_line_wait_on_bit+0x64/0x70) from [<c0110ad8>] (journal_commit_transaction+0x6a0/0x14ac)
> [<c0110ad8>] (journal_commit_transaction+0x6a0/0x14ac) from [<c0113ea4>] (kjournald+0xc0/0x25c)
> [<c0113ea4>] (kjournald+0xc0/0x25c) from [<c0032acc>] (kthread+0x84/0x90)
> [<c0032acc>] (kthread+0x84/0x90) from [<c0009844>] (kernel_thread_exit+0x0/0x8)
> no locks held by kjournald/595.
> INFO: task dd:601 blocked for more than 30 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> dd              D c03bbf14     0   601    586 0x00000000
> [<c03bbf14>] (__schedule+0x220/0x590) from [<c03bc3b0>] (io_schedule+0x60/0x94)
> [<c03bc3b0>] (io_schedule+0x60/0x94) from [<c007104c>] (sleep_on_page+0x8/0x10)
> [<c007104c>] (sleep_on_page+0x8/0x10) from [<c03ba24c>] (__wait_on_bit+0x74/0xb8)
> [<c03ba24c>] (__wait_on_bit+0x74/0xb8) from [<c00712d4>] (wait_on_page_bit+0xbc/0xd0)
> [<c00712d4>] (wait_on_page_bit+0xbc/0xd0) from [<c0071dc4>] (grab_cache_page_write_begin+0x98/0xc4)
> [<c0071dc4>] (grab_cache_page_write_begin+0x98/0xc4) from [<c00fa3cc>] (ext3_write_begin+0x74/0x208)
> [<c00fa3cc>] (ext3_write_begin+0x74/0x208) from [<c007176c>] (generic_file_buffered_write+0x19c/0x260)
> [<c007176c>] (generic_file_buffered_write+0x19c/0x260) from [<c007283c>] (__generic_file_aio_write+0x234/0x490)
> [<c007283c>] (__generic_file_aio_write+0x234/0x490) from [<c0072af8>] (generic_file_aio_write+0x60/0xcc)
> [<c0072af8>] (generic_file_aio_write+0x60/0xcc) from [<c009b990>] (do_sync_write+0xa8/0xdc)
> [<c009b990>] (do_sync_write+0xa8/0xdc) from [<c009c2c0>] (vfs_write+0xa8/0x138)
> [<c009c2c0>] (vfs_write+0xa8/0x138) from [<c009c530>] (sys_write+0x40/0x6c)
> [<c009c530>] (sys_write+0x40/0x6c) from [<c0008ec0>] (ret_fast_syscall+0x0/0x38)
> 1 lock held by dd/601:
>  #0:  (&sb->s_type->i_mutex_key#12){+.+.+.}, at: [<c0072adc>] generic_file_aio_write+0x44/0xcc
> INFO: task mmcqd/0:592 blocked for more than 30 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> 
> 
> With git bisect this issue was boiled down to this commit:
> 
> |   commit 9e15db7ce949e9f2d8bb6ce32a74212a4f662370
> |   Author: Javier Martin <javier.martin@vista-silicon.com>
> |   Date:   Fri Mar 2 09:28:47 2012 +0100
> |
> |       dmaengine: Add support for multiple descriptors for imx-dma.
> |
> |       dmaengine specifies the possibility that several descriptors
> |       can be queued for transfer. It also indicates that tasklets
> |       must be used for DMA callbacks.
> 
> I'm not sure if it only triggers a side effect. Any ideas?
> 
>  Thanks
>   -- Christoph
> 

--