-----Original Message-----
From: Lars-Peter Clausen <lars@metafoo.de>
Sent: Mittwoch, 19. August 2020 13:08
I think this might be an sdma specific problem after all.
dmaengine_terminate_async() will issue a request to stop the DMA. But it
is still safe to issue the next transfer, even without calling
dmaengine_synchronize(). The DMA should start the new transfer at its
earliest convenience in that case.

dmaegine_synchronize() is so that the consumer has a guarantee that the
DMA is finished using the resources (e.g. the memory buffers) associated
with the DMA transfer so it can safely free them.

Thank you for the clarifications!

I don't know how feasible this is to implement in the SDMA dmaengine
driver. But I think what is should do is to have some flag to indicate
if a terminate is in progress. If a new transfer is issued while
terminate is in progress the transfer should go on a list. Once
terminate finishes it should check the list and start the transfer if
there are any on the list.

IMHO that's nearly what Robin's patches does, so this should be sufficient:
Putting the descriptors to free in an extra termination list and ensuring
that a new transfer is handled after the last termination is done.


@Robin:
Is it possible to tag the commits for the stable-tree
Cc: stable@vger.kernel.org?

Best regards and thank you all!
Benjamin
Richard

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