[Sound-open-firmware] First caller of pipeline_copy

[Daniel Baluta]

On Mon, Apr 13, 2020 at 2:16 PM Daniel Baluta <daniel.baluta at gmail.com> wrote:
>
> Hi,
>
> I want to understand how copying data works on a playback pipeline,
> specifically how
> the first bytes are copied.
>
> It looks like SOF_SCHEDULE_LL_DMA scheduler takes care about scheduling
> pipeline_task.
>
> In a simple pipeline with Host <-> (buf0) <-> Volume <->(buf1) DAI the
> data needs to be propagated
> from upstream up to DAI.
>
> DMA is responsible to copy the data from buf1 to DAI. But at the time
> the DMA interrupt
> arrives the data are not yet propagated to buf1.
>
> We would need a way to preload first bytes. But I couldn't find anywhere in the
> code where this happens.

More to add to this: So, basically in our design the DMA controller will send an
interrupt after successfully copied data.

So, in order for this to work the first chunk needs to be preloaded
into buf1. Any suggestion
where to look into the code are welcomed!