Vinod Koul <vinod.koul@xxxxxxxxx> writes: >> Yes, Vinod and and Dan are certainly the best ones to comment on that I >> think. > I read the file esp the "DMA flow" and "DMA hot chaining timeslice issue". I can > say with "properly" implemented dmaengine driver this is very much doable. Great. > > > Have you guys read: Documentation/dmaengine.txt? Yes. I had not understood the "hot chaining" was implied in it, but now I understand it is part of it, and at the discretion of the slave engine driver. > So for "hot chaning" it would work as follows: > > Client, allocates and channel and prepares the descriptors A B & C > Client (video), submits buffer A, Buffer B. Both are queued by dma driver > Client calls dma_async_issue_pending > DMA driver will start Buffer A. It gets the completetion for A and then Starts > B. It will invoke callbakc for A. > > If you submit C, and invoke dma_async_issue_pending(), C is queued > On B completetion, the DMA driver will start C and invoke callback for B. > > If B completes before C is submitted, after submit and invoking > dma_async_issue_pending(), the C buffer will be queued and started. OK, that settles it then. The API allows hot chaining, and if I understand Daniel's driver properly, he already thought about it (in append_pending_queue()). I have some homework now Daniel, I'll send you my work to include into your patch serie for the review, and my tests of your patches. I need a bit of time (1 or 2 weeks), because of holidays, for my patch. Cheers. -- Robert -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
