[alsa-devel] [PATCH] ASoC: dmaengine: add runtime status checking in dmaengine_pcm_dma_complete

[Vinod Koul]

On Mon, Jun 10, 2013 at 12:46:52PM +0200, Lars-Peter Clausen wrote:
> On 06/10/2013 11:31 AM, Mark Brown wrote:
> > On Sun, Jun 09, 2013 at 03:51:09PM +0200, Lars-Peter Clausen wrote:
> >> On 06/09/2013 03:37 PM, Lars-Peter Clausen wrote:
> > 
> >>> I haven't see the original patch, but the proper solution to this problem
> >>> should be to add a check to snd_dmaengine_pcm_close() to see if the DMA is
> >>> still running.
> > 
> >> Ok, since this will never happen, I suppose the problem is rather that the DMA
> >> callback is called after dma_terminate_all() has been called. Which sounds like
> >> it is a bug in the dmaengine driver. And this will likely also be a problem for
> >> other users of that dmaengine driver and not only the ASoC driver, so it should
> >> be fixed in the dmaengine driver.
> > 
> > Just to clarify what is it makes you say that this will never happen?
> 
> At least that is my understanding of snd_pcm_release_substream(), that it
> will first make sure that the stream is stopped, by calling snd_pcm_drop(),
> before closing the stream.
Yes you need to call dmaengine_terminate_all(). But even then we might have
trasaction in flight or some dma controllers cant abort immediately (need to
wait till FIFOs are flushed etc). In general it is a good practice to call
dma_sync_wait() before you tear down the client.
If you still see an issue, then it a buggy driver :)

--
~Vinod