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. -- 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
