[alsa-devel] Query on Audio DMA using DMAEngine

Lars-Peter Clausen lars at metafoo.de
Wed Jul 3 11:09:22 CEST 2013

On 07/02/2013 02:13 PM, Mark Brown wrote:
> On Tue, Jul 02, 2013 at 07:50:16AM +0200, Mike Looijmans wrote:
>> On 07/02/2013 05:33 AM, Joel Fernandes wrote:
>> This meant I had to use a DMA PARAM slot for every "period". The
>> OMAP L138 has 128 of those slots, so it's no problem to use a bunch
>> of them. Because the chain is cyclic, there is no need to update any
>> DMA parameter while running. All that ALSA needs to do is empty the
>> buffer before the cycle completes and the current position gets
>> overwritten.
> This sort of cyclic thing tends to be best, ideally you don't need
> interrupts at all (other than a timer).

Yes, this is usually how it is done. But I'm wondering maybe the EDMA
controller only has a small total amount of slots available.

- Lars

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