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Subject: Re: [PATCH v2] ALSA: hda/tegra: enable clock during probe
To:     Sameer Pujar <spujar@nvidia.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Thierry Reding <thierry.reding@gmail.com>
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From:   Jon Hunter <jonathanh@nvidia.com>
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Date:   Mon, 4 Feb 2019 10:04:50 +0000
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On 04/02/2019 08:16, Sameer Pujar wrote:

...

> Objective is to have things working with or without CONFIG_PM enabled.
> From previous comments and discussions it appears that there is mixed
> response
> for calling hda_tegra_runtime_resume() or runtime PM APIs in probe()
> call. Need
> to have consensus regarding the best practice to be followed, which
> would eventually
> can be used in other drivers too.
>=20
> Rafael is suggesting to use CONFIG_PM check to do manual setup or
> runtime PM setup in probe,
> which would bring back the earlier above mentioned concern.
>=20
> if (IS_ENABLED(CONFIG_PM)) {
> do setup based on pm-runtime
> } else {
> =C2=A0=C2=A0=C2=A0 do manual setup
> }
> Both if/else might end up doing the same here.
> Do we really need CONFIG_PM check here?
>=20
> Instead does below proposal appear fine?
>=20
> probe() {
> =C2=A0=C2=A0=C2=A0 hda_tegra_enable_clock();
> }
>=20
> probe_work() {
> =C2=A0=C2=A0=C2=A0 /* hda setup */
> =C2=A0=C2=A0=C2=A0 . . .
> =C2=A0=C2=A0=C2=A0 pm_runtime_set_active(); /* initial state as active */
> =C2=A0=C2=A0=C2=A0 pm_runtime_enable();
> =C2=A0=C2=A0=C2=A0 return;
> }

I believe that this still does not work, because if there is a
power-domain that needs to be turned on, this does not guarantee this.
So I think that you need to call pm_runtime_get ...

 probe() {
 	if (!IS_ENABLED(CONFIG_PM))
 		hda_tegra_enable_clock();
 }


 probe_work() {
    	/* hda setup */
    	. . .
	pm_runtime_enable();
	pm_runtime_get_sync();
	return;
 }

The alternative here could just be ...

 probe() {
	pm_runtime_enable();
 	if (!pm_runtime_enabled())
 		ret =3D hda_tegra_enable_clock();
	else
		ret =3D pm_runtime_get_sync();

	if (ret < 0) {
		...
	}
 }

Very similar to what I was saying to begin with but not call the
pm_runtime_resume handler directly. Which I believe was Iwai-san's dislike.

Cheers
Jon

--=20
nvpublic