[PATCH 00/20] ARM: pxa: move core and drivers to dmaengine

Vinod Koul [off-list ref] writes:

quoted

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