[Sound-open-firmware] First caller of pipeline_copy

[Daniel Baluta]

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.