Re: About snd_soc_dai_set_fmt()

[Shengjiu Wang <shengjiu.wang@xxxxxxxxx>]

On Thu, Jun 6, 2024 at 7:09 PM Mark Brown <broonie@xxxxxxxxxx> wrote:
>
> On Thu, Jun 06, 2024 at 06:55:29PM +0800, Shengjiu Wang wrote:
> > On Wed, Jun 5, 2024 at 7:40 PM Mark Brown <broonie@xxxxxxxxxx> wrote:
>
> > > Do you have an example of such a use case?  If you can do that it feels
> > > more like one end has two single direction DAIs (ISTR some of the
> > > Freescale platforms were built like that?) and it might be better to do
> > > that and make it easier to combine two DAIs.  That would also work for
> > > things like combining dedicated DACs and ADCs.
>
> > one of case is:
> >
> > +-------+                +-----------------+
> > | SAI1  |   --TX-->  |                     |
> > |           |   <--RX-- |                     |
> > +-------+                |                     |
> >                              | AUDIOMIX  |
> > +-------+                |                     |
> > | SAI2  |   --TX-->  |                    |
> > +-------+                +----------------+
>
> > AUDIOMIX mixes the output of SAI1 and SAI2,  AUDIOMIX's output
> > is sent to SAI1.
>
> So that's a DPCM case but hitting the DPCM scaling limits.  One of these
> days someone will actually have a use case that generates enough pull to
> get digital routing done...
>
> > Use multi-DAI may be an option,  but for fsl_sai driver, in some cases it
> > is used as single DAI.  So how to support single DAI and multi-DAI in one
> > driver?  Should we define a new dts property to distinguish these two cases
> > in order to register different component + dai driver?
>
> Some drivers have bodged it by adding 3 DAIs, one bidirectional and the
> other two unidirectional and relying on users to DTRT.  Nothing is super
> great there.

With multi-DAI,  there will be three devices,  hw:0,0 for SAI1 TX,  hw:0,1
for SAI2 TX,  hw:0,2 for SAI1 RX. Which means the SAI1 TX and SAI1 RX
are in different devices.  Can we let SAI1 TX and SAI RX in the same hw
device?

best regards
Shengjiu Wang