dmaengine, virt-dma and reusable transfers

Commit Message

Robert Jarzmik Feb. 22, 2015, 4:41 p.m. UTC

Hi Russell and Vinod,

I've made the patch in [1] in order to be able to reuse descriptors,
ie. resubmit completed transfers once they are completed.

As I'm not sure I understand all the dmaengine slave API, nor the virt-dma
fully, I'd like you to have an eye on it first.

Thanks for your time.

Patch

diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c
index 6f80432..1e4fd18 100644
--- a/drivers/dma/virt-dma.c
+++ b/drivers/dma/virt-dma.c
@@ -83,8 +83,10 @@  static void vchan_complete(unsigned long arg)
 		cb_data = vd->tx.callback_param;
 
 		list_del(&vd->node);
-
-		vc->desc_free(vd);
+		if (vd->tx.flags & DMA_PREP_CONTINUE)
+			list_add(&vd->node, &vc->desc_submittable);
+		else
+			vc->desc_free(vd);
 
 		if (cb)
 			cb(cb_data);
@@ -108,6 +110,7 @@  void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev)
 	dma_cookie_init(&vc->chan);
 
 	spin_lock_init(&vc->lock);
+	INIT_LIST_HEAD(&vc->desc_submittable);
 	INIT_LIST_HEAD(&vc->desc_submitted);
 	INIT_LIST_HEAD(&vc->desc_issued);
 	INIT_LIST_HEAD(&vc->desc_completed);
diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
index 181b952..3772032 100644
--- a/drivers/dma/virt-dma.h
+++ b/drivers/dma/virt-dma.h
@@ -29,6 +29,7 @@  struct virt_dma_chan {
 	spinlock_t lock;
 
 	/* protected by vc.lock */
+	struct list_head desc_submittable;
 	struct list_head desc_submitted;
 	struct list_head desc_issued;
 	struct list_head desc_completed;
@@ -134,6 +135,7 @@  static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
 static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
 	struct list_head *head)
 {
+	list_splice_tail_init(&vc->desc_submittable, head);
 	list_splice_tail_init(&vc->desc_submitted, head);
 	list_splice_tail_init(&vc->desc_issued, head);
 	list_splice_tail_init(&vc->desc_completed, head);