Question about snd_soc_card_register()

[Ranjani Sridharan]

On Thu, 2020-04-16 at 09:04 +0200, Takashi Iwai wrote:
> On Thu, 16 Apr 2020 07:52:45 +0200,
> Sridharan, Ranjani wrote:
> > 
> > Hi Takashi,
> > 
> > While working on implementing the probes features in SOF using a
> > separate card
> > for the probe DAI links, I noticed that calling
> > snd_soc_register_card() 
> > results in
> > incrementing the usage_count for the device that registers the card
> > by 2 and
> > it is not decremented until the card is freed.
> > 
> > Is this the expected behaviour? Typically, we register a separate
> > platform
> > device for the Intel machines which in turn register the card and
> > none of them
> > ever enable runtime PM. So this has no impact on the parent
> > device's runtime
> > PM status. 
> > 
> > I'd like to avoid creating a separate platform device just to
> > register the
> > card if possible while also enabling runtime PM . But when I do
> > this today,
> > the device cannot enter runtime suspend at all. Could you please
> > shed some
> > light on this?
> 
> It's not clear how you see the things.  Which device are you looking
> at?  Typically a card object points to two different devices, one is 
> the real device that the chip belongs to (card->dev), and another the
> own device object for managing the device files (card.card_dev).
> And in general, snd_soc_card_register() or snd_card_register() don't
> manipulate the runtime PM stuff by itself at all.

Its the card->dev that I am looking at. This is the device that calls
devm_snd_soc_register_card(). 
In my tests, the usage_count for this device is 0 before calling
devm_snd_soc_register_card and it is 2 after the card registration is
complete.

Thanks,
Ranjani