Skip to content

Commit

Permalink
dmaengine: virt-dma: add support for cyclic DMA periodic callbacks
Browse files Browse the repository at this point in the history
Add support for cyclic DMA's periodic callbacks.  Drivers are expected
to call vchan_cyclic_callback() when a period has completed, which will
schedule the tasklet to make the callback into the driver.

As callbacks are made from tasklet context, it is important to realise
that we don't guarantee a callback for each completed period, but for
N completed periods where N may be greater than one.

Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
  • Loading branch information
Russell King committed Jul 1, 2012
1 parent fe04587 commit 571fa74
Show file tree
Hide file tree
Showing 2 changed files with 29 additions and 4 deletions.
19 changes: 15 additions & 4 deletions drivers/dma/virt-dma.c
Original file line number Diff line number Diff line change
Expand Up @@ -59,17 +59,28 @@ EXPORT_SYMBOL_GPL(vchan_find_desc);
static void vchan_complete(unsigned long arg)
{
struct virt_dma_chan *vc = (struct virt_dma_chan *)arg;
struct virt_dma_desc *vd;
dma_async_tx_callback cb = NULL;
void *cb_data = NULL;
LIST_HEAD(head);

spin_lock_irq(&vc->lock);
list_splice_tail_init(&vc->desc_completed, &head);
vd = vc->cyclic;
if (vd) {
vc->cyclic = NULL;
cb = vd->tx.callback;
cb_data = vd->tx.callback_param;
}
spin_unlock_irq(&vc->lock);

if (cb)
cb(cb_data);

while (!list_empty(&head)) {
struct virt_dma_desc *vd = list_first_entry(&head,
struct virt_dma_desc, node);
dma_async_tx_callback cb = vd->tx.callback;
void *cb_data = vd->tx.callback_param;
vd = list_first_entry(&head, struct virt_dma_desc, node);
cb = vd->tx.callback;
cb_data = vd->tx.callback_param;

list_del(&vd->node);

Expand Down
14 changes: 14 additions & 0 deletions drivers/dma/virt-dma.h
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,8 @@ struct virt_dma_chan {
struct list_head desc_submitted;
struct list_head desc_issued;
struct list_head desc_completed;

struct virt_dma_desc *cyclic;
};

static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan)
Expand Down Expand Up @@ -91,6 +93,18 @@ static inline void vchan_cookie_complete(struct virt_dma_desc *vd)
tasklet_schedule(&vc->task);
}

/**
* vchan_cyclic_callback - report the completion of a period
* vd: virtual descriptor
*/
static inline void vchan_cyclic_callback(struct virt_dma_desc *vd)
{
struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);

vc->cyclic = vd;
tasklet_schedule(&vc->task);
}

/**
* vchan_next_desc - peek at the next descriptor to be processed
* vc: virtual channel to obtain descriptor from
Expand Down

0 comments on commit 571fa74

Please sign in to comment.