[alsa-devel] [PATCH 19/19] ASoC: fsi: Add DMAEngine support

Vinod Koul vinod.koul at linux.intel.com
Mon Feb 6 15:46:00 CET 2012

On Mon, 2012-02-06 at 09:47 +0100, Lars-Peter Clausen wrote:
> On 02/04/2012 07:40 PM, Vinod Koul wrote:
> >[...]
> > 
> > And while at it, I believe for this use, terminate_all is too strong an
> > API to be used, perhaps we should introduce a STOP call, which just
> > aborts the current descriptor but doesn't free it, or possibly move to
> > submitted state/queue. And yes terminate_all should used in scenarios
> > like free callback.
> > That way it should map properly to ALSA PCM operations.
> > 
> Yes, a call that would allow us to reset/restart a transfer would be nice.
> While we are at it: Another nice addition, which would be good for sound
> drivers is a callback, which reports the transfer's current position in the
> datastream. This allows us to implement a pointer callback with sub-period
> granularity and also allow us to implement the 'no period wakeup' feature. A
> lot of DMA controllers support reporting this, but as far as I can see there
> is currently no way to export this information using dmaengine.
What makes you think it's missing :-)

Pls see device_tx_status callback. You can return the descriptor
position using this and enable "no wake mode"
> - Lars


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