From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH v2] ALSA: hda/tegra: enable clock during probe Date: Thu, 31 Jan 2019 12:05:30 +0100 Message-ID: <20190131110530.GA23438@ulmo> References: <1548414418-5785-1-git-send-email-spujar@nvidia.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="+QahgC5+KEYLbs62" Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Takashi Iwai , "Rafael J. Wysocki" Cc: Jon Hunter , pierre-louis.bossart@linux.intel.com, Sameer Pujar , perex@perex.cz, alsa-devel@alsa-project.org, mkumard@nvidia.com, rlokhande@nvidia.com, sharadg@nvidia.com, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, linux-pm@vger.kernel.org List-Id: linux-pm@vger.kernel.org --+QahgC5+KEYLbs62 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jan 30, 2019 at 05:40:42PM +0100, Takashi Iwai wrote: > On Wed, 30 Jan 2019 13:45:49 +0100, > Jon Hunter wrote: > >=20 > >=20 > > On 25/01/2019 11:06, Sameer Pujar wrote: > > > If CONFIG_PM is disabled or runtime PM calls are forbidden, the clocks > > > will not be ON. This could cause issue during probe, where hda init > > > setup is done. This patch enables clocks unconditionally during probe. > > >=20 > > > Along with above, follwoing changes are done. > > > * enable runtime PM before exiting from probe work. This helps to a= void > > > usage of pm_runtime_get_sync/pm_runtime_put() in probe work. > > > * hda_tegra_disable_clocks() is moved out of CONFIG_PM_SLEEP check. > > > * runtime PM callbacks moved out of CONFIG_PM check > > >=20 > > > Signed-off-by: Sameer Pujar > > > Reviewed-by: Ravindra Lokhande > > > Reviewed-by: Jon Hunter > > > --- > > > sound/pci/hda/hda_tegra.c | 26 +++++++++++++++++--------- > > > 1 file changed, 17 insertions(+), 9 deletions(-) > > >=20 > > > diff --git a/sound/pci/hda/hda_tegra.c b/sound/pci/hda/hda_tegra.c > > > index c8d18dc..ba6175f 100644 > > > --- a/sound/pci/hda/hda_tegra.c > > > +++ b/sound/pci/hda/hda_tegra.c > > > @@ -219,7 +219,6 @@ static int hda_tegra_enable_clocks(struct hda_teg= ra *data) > > > return rc; > > > } > > > =20 > > > -#ifdef CONFIG_PM_SLEEP > > > static void hda_tegra_disable_clocks(struct hda_tegra *data) > > > { > > > clk_disable_unprepare(data->hda2hdmi_clk); > > > @@ -227,6 +226,7 @@ static void hda_tegra_disable_clocks(struct hda_t= egra *data) > > > clk_disable_unprepare(data->hda_clk); > > > } > > > =20 > > > +#ifdef CONFIG_PM_SLEEP > > > /* > > > * power management > > > */ > > > @@ -257,7 +257,6 @@ static int hda_tegra_resume(struct device *dev) > > > } > > > #endif /* CONFIG_PM_SLEEP */ > > > =20 > > > -#ifdef CONFIG_PM > > > static int hda_tegra_runtime_suspend(struct device *dev) > > > { > > > struct snd_card *card =3D dev_get_drvdata(dev); > > > @@ -283,7 +282,7 @@ static int hda_tegra_runtime_resume(struct device= *dev) > > > int rc; > > > =20 > > > rc =3D hda_tegra_enable_clocks(hda); > > > - if (rc !=3D 0) > > > + if (rc) > > > return rc; > > > if (chip && chip->running) { > > > hda_tegra_init(hda); > > > @@ -292,7 +291,6 @@ static int hda_tegra_runtime_resume(struct device= *dev) > > > =20 > > > return 0; > > > } > > > -#endif /* CONFIG_PM */ > > > =20 > > > static const struct dev_pm_ops hda_tegra_pm =3D { > > > SET_SYSTEM_SLEEP_PM_OPS(hda_tegra_suspend, hda_tegra_resume) > > > @@ -551,9 +549,9 @@ static int hda_tegra_probe(struct platform_device= *pdev) > > > =20 > > > dev_set_drvdata(&pdev->dev, card); > > > =20 > > > - pm_runtime_enable(hda->dev); > > > - if (!azx_has_pm_runtime(chip)) > > > - pm_runtime_forbid(hda->dev); > > > + err =3D hda_tegra_enable_clocks(hda); > > > + if (err) > > > + goto out_free; > >=20 > > We also need to think about power-domains here. Enabling the clocks > > might not be enough as the appropriate power-domain needs to be enabled. > > For 64-bit Tegra runtime-pm will handle the power-domains (assuming they > > are populated in device-tree). So I still think it is better we call > > pm_runtime_get_sync() at some point rather than just replying on > > enabling the clocks. >=20 > If I understand correctly the code, the pm domain is already activated > at calling driver's probe callback. As far as I can tell, the domain will also be powered off again after probe finished, unless the device grabs a runtime PM reference. This is what happens via the dev->pm_domain->sync() call after successful probe of a driver. It seems to me like it's not a very well defined case what to do when a device needs to be powered up but runtime PM is not enabled. Adding Rafael and linux-pm, maybe they can provide some guidance on what to do in these situations. To summarize, what we're debating here is how to handle powering up a device if the pm_runtime infrastructure doesn't take care of it. Jon's proposal here was, and we use this elsewhere, to do something like this: pm_runtime_enable(dev); if (!pm_runtime_enabled(dev)) { err =3D foo_runtime_resume(dev); if (err < 0) goto fail; } So basically when runtime PM is not available, we explicitly "resume" the device to power it up. It seems to me like that's a fairly common problem, so I'm wondering if there's something that the runtime PM core could do to help with this. Or perhaps there's already a way to achieve this that we're all overlooking? Rafael, any suggestions? 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