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SubjectRe: [PATCH 1/3] dmaengine: virt-dma: don't always free descriptor upon completion
On Sun, Sep 06, 2015 at 01:40:52PM +0200, Robert Jarzmik wrote:
> @@ -29,7 +29,7 @@ dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *tx)
> spin_lock_irqsave(&vc->lock, flags);
> cookie = dma_cookie_assign(tx);
>
> - list_add_tail(&vd->node, &vc->desc_submitted);
> + list_move_tail(&vd->node, &vc->desc_submitted);

I am not sure I follow this, why move ?

> +int vchan_tx_desc_free(struct dma_async_tx_descriptor *tx)
> +{
> + struct virt_dma_chan *vc = to_virt_chan(tx->chan);
> + struct virt_dma_desc *vd = to_virt_desc(tx);
> + unsigned long flags;
> +
> + spin_lock_irqsave(&vc->lock, flags);
> + list_del(&vd->node);
> + spin_unlock_irqrestore(&vc->lock, flags);
> +
> + dev_dbg(vc->chan.device->dev, "vchan %p: txd %p[%x]: freeing\n",
> + vc, vd, vd->tx.cookie);
> + vc->desc_free(vd);
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(vchan_tx_desc_free);
this one seems okay, can you add comments here and also update documentation
for this

> @@ -96,9 +115,13 @@ void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head)
> while (!list_empty(head)) {
> struct virt_dma_desc *vd = list_first_entry(head,
> struct virt_dma_desc, node);
> - list_del(&vd->node);
> - dev_dbg(vc->chan.device->dev, "txd %p: freeing\n", vd);
> - vc->desc_free(vd);
> + if (dmaengine_desc_test_reuse(&vd->tx)) {
> + list_move_tail(&vd->node, &vc->desc_allocated);

should we check this if the list is to be freed? Why would anyone call free
except when cleaning up ?

> static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
> {
> + struct virt_dma_desc *vd;
> unsigned long flags;
> LIST_HEAD(head);
>
> spin_lock_irqsave(&vc->lock, flags);
> vchan_get_all_descriptors(vc, &head);
> + list_for_each_entry(vd, &head, node)
> + dmaengine_desc_clear_reuse(&vd->tx);

why do we want to do this, if we are freeing them

--
~Vinod


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