[PATCH] dmaengine: bcm2835-dma: Convert to use DMA pool
Peter Ujfalusi
peter.ujfalusi at ti.com
Mon Nov 16 23:46:12 PST 2015
Hi,
On 11/16/2015 01:09 PM, Peter Ujfalusi wrote:
> 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.
FWIW: the patch has been tested and verified on Raspbery Pi:
https://github.com/raspberrypi/linux/pull/1178#issuecomment-157026794
https://github.com/raspberrypi/linux/pull/1178#issuecomment-157030190
It needed some modification since the Raspberry Pi kernel have non upstreamed
changes in bcm2835-dma driver (slave_sg support for example).
It would be great if this patch can make it to 4.4 as a fix.
Thanks,
Péter
>
> Fixes: f93178291712 ("dmaengine: bcm2835-dma: Fix memory leak when stopping a running transfer")
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi at 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 out if 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,
>
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