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

[Qiao Zhou]

On 06/12/2013 10:39 PM, Mark Brown wrote:
> On Wed, Jun 12, 2013 at 02:15:24PM +0200, Lars-Peter Clausen wrote:
>> On 06/12/2013 09:43 AM, Vinod Koul wrote:
>
>>> 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 :)
>
>> Even though if the driver can't abort the transfer immediately, I'd still
>> expect to not see any calls to the descriptors callback after
>> dmaengine_terminate_all() has been called.
>
> It'd certainly be much less surprising - if something's terminated it
> really oughtn't to be generating callbacks.
>
>> We should probably still call dma_sync_wait() though before we free any of
>> the DMA transfer buffers. But I guess this will open a whole new can of
>> bugs, since none of the drivers actually seem to mark a descriptor as
>> completed if the transfer is aborted using dmaengine_terminate_all()
>
> Oh joy.
>
Mark, Lars, Vinod

Indeed it's a DMA handling issue, and I'm preparing to implement a 
proper handling in DMA driver. thanks a lot for these suggestions.
-- 

Best Regards
Qiao