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authorRobert Jarzmik <robert.jarzmik@free.fr>2015-05-26 23:06:33 +0200
committerVinod Koul <vinod.koul@intel.com>2015-06-17 22:15:59 +0530
commitb9855f03d560d351e95301b9de0bc3cad3b31fe9 (patch)
treee13e2f35ed86239fdd3fbf882023daff6802ca5c /drivers/dma/virt-dma.h
parente1031dc1f7ba5c8724ba211062134076df292791 (diff)
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dmaengine: virt-dma: don't always free descriptor upon completion
This patch attempts to enhance the case of a transfer submitted multiple times, and where the cost of creating the descriptors chain is not negligible. This happens with big video buffers (several megabytes, ie. several thousands of linked descriptors in one scatter-gather list). In these cases, a video driver would want to do : - tx = dmaengine_prep_slave_sg() - dma_engine_submit(tx); - dma_async_issue_pending() - wait for video completion - read video data (or not, skipping a frame is also possible) - dma_engine_submit(tx) => here, the descriptors chain recalculation will take time => the dma coherent allocation over and over might create holes in the dma pool, which is counter-productive. - dma_async_issue_pending() - etc ... In order to cope with this case, virt-dma is modified to prevent freeing the descriptors upon completion if DMA_CTRL_ACK flag is set in the transfer. Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'drivers/dma/virt-dma.h')
-rw-r--r--drivers/dma/virt-dma.h13
1 files changed, 12 insertions, 1 deletions
diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
index 181b95267866..189e75dbcb15 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_allocated;
struct list_head desc_submitted;
struct list_head desc_issued;
struct list_head desc_completed;
@@ -55,11 +56,16 @@ static inline struct dma_async_tx_descriptor *vchan_tx_prep(struct virt_dma_chan
struct virt_dma_desc *vd, unsigned long tx_flags)
{
extern dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *);
+ unsigned long flags;
dma_async_tx_descriptor_init(&vd->tx, &vc->chan);
vd->tx.flags = tx_flags;
vd->tx.tx_submit = vchan_tx_submit;
+ spin_lock_irqsave(&vc->lock, flags);
+ list_add_tail(&vd->node, &vc->desc_allocated);
+ spin_unlock_irqrestore(&vc->lock, flags);
+
return &vd->tx;
}
@@ -122,7 +128,8 @@ static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
}
/**
- * vchan_get_all_descriptors - obtain all submitted and issued descriptors
+ * vchan_get_all_descriptors - obtain all allocated, submitted and issued
+ * descriptors
* vc: virtual channel to get descriptors from
* head: list of descriptors found
*
@@ -134,6 +141,7 @@ 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_allocated, 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);
@@ -141,11 +149,14 @@ static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
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)
+ async_tx_clear_ack(&vd->tx);
spin_unlock_irqrestore(&vc->lock, flags);
vchan_dma_desc_free_list(vc, &head);