[alsa-devel] [PATCH v2] ASoC: SGTL5000: Fix kernel failed while trying to get optional VDDD supply.

Li Xiubo Li.Xiubo at freescale.com
Tue Dec 3 10:49:47 CET 2013

> > +static int sgtl5000_external_vddd_used(struct snd_soc_codec *codec) {
> > +	struct regulator *consumer;
> > +	struct sgtl5000_priv *sgtl5000 = snd_soc_codec_get_drvdata(codec);
> > +
> > +	consumer = regulator_get_optional(codec->dev,
> > +			sgtl5000->supplies[VDDD].supply);
> > +	if (IS_ERR(consumer))
> > +		return 0;
> > +
> > +	regulator_put(consumer);
> > +
> > +	return 1;
> > +}
> This is broken with respect to deferred probe, deferred probe returns an
> error when an external regulator is in use but not yet registered.
> The driver needs to at least handle -EPROBE_DEFER specially here.

Well, as we can see that:
1, If the dev has no regulator dt node, a -ENODEV error will be returned. 
2, If the regulator dt node is exist but the optional VDDD is absent (i.e.
The external VDDD is not used), a -EPROBE_DEFER will be returned, if just
return the -EPROBE_DEFER to the probe(and then the probe deferral
mechanism will do the probe again later, is that right ?), and then the
regulator_get_optional() will be called later again, and the -EPROBE_DEFER
will be returned again too, and now how should I handle -EPROBE_DEFER error
twice ? Or should there be a counter about this ? That to say when the
-EPROBE_DEFER error is the second time returned from regulator_get_optional()
can we ensure that the optional VDDD is really not in use.

That's also to say, the regulator_get_optional() must be called twice then
could we know whether the optional external VDDD is really in use or not by
using one counter here.

Or maybe adding a counter in regulator_get_optional() is better.

And do you have any other suggestions to deal with this ?

> It's also not nice to get the regulator, release it and get it again which
> you end up needing to do because...

I have also considered about this. Because if the regulator_bulk_get()
has failed to get the other supplies, the optional one should be released too.
And it can be more easy to deal with.

Yes, this is not very nice and I will revise this.

> > -	ret = regulator_bulk_get(codec->dev, ARRAY_SIZE(sgtl5000->supplies),
> > +	if (sgtl5000_external_vddd_used(codec)) {
> > +		ret = regulator_bulk_get(codec->dev,
> > +				ARRAY_SIZE(sgtl5000->supplies),
> >  				sgtl5000->supplies);
> ...I think my previous comments about this code being poorly structured in
> the existing driver stand.  The bulk get should be used for the supplies
> that are always needed and a separate optional get should be used for this
> one.

Yes, it's.

Best Regards,

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