> -----Original Message----- > From: Lars-Peter Clausen <lars@xxxxxxxxxx> > 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@xxxxxxxxxxxxxxx? Best regards and thank you all! Benjamin Richard
