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Subject[PATCH] dmaengine: bcm2835-dma: Convert to use DMA pool
Date
f93178291712 dmaengine: bcm2835-dma: Fix memory leak when stopping a
running transfer

Fixed the memleak, but introduced another issue: the terminate_all callback
might be called with interrupts disabled and the dma_free_coherent() is
not allowed to be called when IRQs are disabled.
Convert the driver to use dma_pool_* for managing the list of control
blocks for the transfer.

Fixes: f93178291712 ("dmaengine: bcm2835-dma: Fix memory leak when stopping a running transfer")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
---
Hi,

It was brought to my attention that the memleak fix broke the bcm2835 DMA. I did
not noticed the use of dma_free_coherent() in the driver when I did the memleak
fix.
Since the driver does leaking memory every time the audio is stopped, the other
option is to convert it to use DMA pool.
I do not have access the Raspberry Pi, so I can not test this patch but it
compiles ;)
Can someone test this one outif it is working?

Regards,
Peter

drivers/dma/bcm2835-dma.c | 78 ++++++++++++++++++++++++++++++++---------------
1 file changed, 54 insertions(+), 24 deletions(-)

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index c92d6a70ccf3..996c4b00d323 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -31,6 +31,7 @@
*/
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
+#include <linux/dmapool.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
@@ -62,6 +63,11 @@ struct bcm2835_dma_cb {
uint32_t pad[2];
};

+struct bcm2835_cb_entry {
+ struct bcm2835_dma_cb *cb;
+ dma_addr_t paddr;
+};
+
struct bcm2835_chan {
struct virt_dma_chan vc;
struct list_head node;
@@ -72,18 +78,18 @@ struct bcm2835_chan {

int ch;
struct bcm2835_desc *desc;
+ struct dma_pool *cb_pool;

void __iomem *chan_base;
int irq_number;
};

struct bcm2835_desc {
+ struct bcm2835_chan *c;
struct virt_dma_desc vd;
enum dma_transfer_direction dir;

- unsigned int control_block_size;
- struct bcm2835_dma_cb *control_block_base;
- dma_addr_t control_block_base_phys;
+ struct bcm2835_cb_entry *cb_list;

unsigned int frames;
size_t size;
@@ -143,10 +149,13 @@ static inline struct bcm2835_desc *to_bcm2835_dma_desc(
static void bcm2835_dma_desc_free(struct virt_dma_desc *vd)
{
struct bcm2835_desc *desc = container_of(vd, struct bcm2835_desc, vd);
- dma_free_coherent(desc->vd.tx.chan->device->dev,
- desc->control_block_size,
- desc->control_block_base,
- desc->control_block_base_phys);
+ int i;
+
+ for (i = 0; i < desc->frames; i++)
+ dma_pool_free(desc->c->cb_pool, desc->cb_list[i].cb,
+ desc->cb_list[i].paddr);
+
+ kfree(desc->cb_list);
kfree(desc);
}

@@ -199,7 +208,7 @@ static void bcm2835_dma_start_desc(struct bcm2835_chan *c)

c->desc = d = to_bcm2835_dma_desc(&vd->tx);

- writel(d->control_block_base_phys, c->chan_base + BCM2835_DMA_ADDR);
+ writel(d->cb_list[0].paddr, c->chan_base + BCM2835_DMA_ADDR);
writel(BCM2835_DMA_ACTIVE, c->chan_base + BCM2835_DMA_CS);
}

@@ -232,9 +241,16 @@ static irqreturn_t bcm2835_dma_callback(int irq, void *data)
static int bcm2835_dma_alloc_chan_resources(struct dma_chan *chan)
{
struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
+ struct device *dev = c->vc.chan.device->dev;
+
+ dev_dbg(dev, "Allocating DMA channel %d\n", c->ch);

- dev_dbg(c->vc.chan.device->dev,
- "Allocating DMA channel %d\n", c->ch);
+ c->cb_pool = dma_pool_create(dev_name(dev), dev,
+ sizeof(struct bcm2835_dma_cb), 0, 0);
+ if (!c->cb_pool) {
+ dev_err(dev, "unable to allocate descriptor pool\n");
+ return -ENOMEM;
+ }

return request_irq(c->irq_number,
bcm2835_dma_callback, 0, "DMA IRQ", c);
@@ -246,6 +262,7 @@ static void bcm2835_dma_free_chan_resources(struct dma_chan *chan)

vchan_free_chan_resources(&c->vc);
free_irq(c->irq_number, c);
+ dma_pool_destroy(c->cb_pool);

dev_dbg(c->vc.chan.device->dev, "Freeing DMA channel %u\n", c->ch);
}
@@ -261,8 +278,7 @@ static size_t bcm2835_dma_desc_size_pos(struct bcm2835_desc *d, dma_addr_t addr)
size_t size;

for (size = i = 0; i < d->frames; i++) {
- struct bcm2835_dma_cb *control_block =
- &d->control_block_base[i];
+ struct bcm2835_dma_cb *control_block = d->cb_list[i].cb;
size_t this_size = control_block->length;
dma_addr_t dma;

@@ -343,6 +359,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
dma_addr_t dev_addr;
unsigned int es, sync_type;
unsigned int frame;
+ int i;

/* Grab configuration */
if (!is_slave_direction(direction)) {
@@ -374,27 +391,31 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
if (!d)
return NULL;

+ d->c = c;
d->dir = direction;
d->frames = buf_len / period_len;

- /* Allocate memory for control blocks */
- d->control_block_size = d->frames * sizeof(struct bcm2835_dma_cb);
- d->control_block_base = dma_zalloc_coherent(chan->device->dev,
- d->control_block_size, &d->control_block_base_phys,
- GFP_NOWAIT);
-
- if (!d->control_block_base) {
+ d->cb_list = kcalloc(d->frames, sizeof(*d->cb_list), GFP_KERNEL);
+ if (!d->cb_list) {
kfree(d);
return NULL;
}
+ /* Allocate memory for control blocks */
+ for (i = 0; i < d->frames; i++) {
+ struct bcm2835_cb_entry *cb_entry = &d->cb_list[i];
+
+ cb_entry->cb = dma_pool_zalloc(c->cb_pool, GFP_ATOMIC,
+ &cb_entry->paddr);
+ if (!cb_entry->cb)
+ goto error_cb;
+ }

/*
* Iterate over all frames, create a control block
* for each frame and link them together.
*/
for (frame = 0; frame < d->frames; frame++) {
- struct bcm2835_dma_cb *control_block =
- &d->control_block_base[frame];
+ struct bcm2835_dma_cb *control_block = d->cb_list[frame].cb;

/* Setup adresses */
if (d->dir == DMA_DEV_TO_MEM) {
@@ -428,12 +449,21 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
* This DMA engine driver currently only supports cyclic DMA.
* Therefore, wrap around at number of frames.
*/
- control_block->next = d->control_block_base_phys +
- sizeof(struct bcm2835_dma_cb)
- * ((frame + 1) % d->frames);
+ control_block->next = d->cb_list[((frame + 1) % d->frames)].paddr;
}

return vchan_tx_prep(&c->vc, &d->vd, flags);
+error_cb:
+ i--;
+ for (; i >= 0; i--) {
+ struct bcm2835_cb_entry *cb_entry = &d->cb_list[i];
+
+ dma_pool_free(c->cb_pool, cb_entry->cb, cb_entry->paddr);
+ }
+
+ kfree(d->cb_list);
+ kfree(d);
+ return NULL;
}

static int bcm2835_dma_slave_config(struct dma_chan *chan,
--
2.6.2


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