On Mon, Aug 04, 2014 at 06:50:17PM +0200, Laurent Pinchart wrote: > The question was why is there a dma_async_issue_pending() operation at all ? > Why can't dmaengine_submit() triggers the transfer start ? The only > explanation is a small comment in dmaengine.h that states > > * This allows drivers to push copies to HW in batches, > * reducing MMIO writes where possible. > > I don't think that's applicable for DMA slave transfers. Is it still > applicable for anything else ? why not? If your hw supports sg-lists and say length of 8 and you prepare two descriptors for lengths of 3 and 5. While in issue pending what prevents you from submiiting them in one shot to hardware while still getting interrupt. I know designware and intel-dma do support that. It is different point that drivers don't -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
