Hi Lars, On Thursday 15 October 2015 09:35:31 Lars-Peter Clausen wrote: > On 10/15/2015 05:56 AM, Vinod Koul wrote: > > On Wed, Oct 14, 2015 at 01:02:22PM +0200, Lars-Peter Clausen wrote: > >> On 10/14/2015 12:50 PM, Vinod Koul wrote: > >>> On Thu, Oct 08, 2015 at 04:51:30PM +0200, Lars-Peter Clausen wrote: > >>>>> The DMA engine API states that > >>>>> > >>>>> * device_terminate_all > >>>>> > >>>>> - Aborts all the pending and ongoing transfers on the channel > >>>>> - This command should operate synchronously on the channel, > >>>>> terminating right away all the channels > >>>>> > >>>>> I wonder how to interpret "synchronously" here, should terminate_all() > >>>>> wait for termination to be complete ? In that case it wouldn't be > >>>>> valid to call it from non-sleepable context. > >>>> > >>>> We need to extend the DMAengine API to allow synchronization. The issue > >>>> is not only the IRQ itself but also the tasklet that can be scheduled > >>>> from the IRQ. Since we in some cases (e.g. audio underrun) call > >>>> terminate_all() from within the completion callback that runs in the in > >>>> the tasklet we can't synchronize to the tasklet in > >>>> dmaengine_terminate_all(). We need a separate API call to handle this. > >>>> And then maybe have a helper like dmaengine_terminate_all_sync() that > >>>> terminates and synchronizes. And in cases where terminate_all is called > >>>> from a context where it can't synchronize the new API needs to be > >>>> called separately before freeing the resources. > >>> > >>> Right now the terminate_all() is intended for syncronous behaviour which > >>> prevents it from being invoked in the callback. > >> > >> That does not match reality though. Which means the documentation is > >> wrong. Pretty much all drivers implement a non-synchronous terminate > >> function and there are users that rely on this. > > > > Lets fix that then :) > > > > We should have both option IMHO, as I think we have both types of > > usages... Care to send a patch? > > Yeah, it's on my TODO list for the next month, since I need the synchronous > terminate elsewhere as well. The DMA engine API needs lots of love. Should we try to synchronize on all the open issues to define a coherent direction ? -- Regards, Laurent Pinchart -- 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
