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From:   Luca Weiss <luca@z3ntu.xyz>
To:     Pavel Machek <pavel@ucw.cz>, ~postmarketos/upstreaming@lists.sr.ht
Cc:     "Lin, Meng-Bo" <linmengbo0689@protonmail.com>,
        linux-kernel@vger.kernel.org, Lee Jones <lee@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Nikita Travkin <nikita@trvn.ru>, linux-leds@vger.kernel.org,
        devicetree@vger.kernel.org, ~postmarketos/upstreaming@lists.sr.ht,
        Stephan Gerhold <stephan@gerhold.net>
Subject: Re: [PATCH v2 2/2] leds: aw2013: Add vddio regulator
Date:   Wed, 29 Mar 2023 18:54:54 +0200
Message-ID: <2672233.mvXUDI8C0e@z3ntu.xyz>
In-Reply-To: <ZB1gNJBFeFSdagF1@gerhold.net>
References: <20230320174949.174600-1-linmengbo0689@protonmail.com>
 <ZByp5gzspOVcYyah@duo.ucw.cz> <ZB1gNJBFeFSdagF1@gerhold.net>
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On Freitag, 24. M=E4rz 2023 09:32:52 CEST Stephan Gerhold wrote:
> Hi Pavel,
>=20
> On Thu, Mar 23, 2023 at 08:35:02PM +0100, Pavel Machek wrote:
> > > Some LEDs controllers are used with external pull-up for the interrupt
> > > line and the I2C lines, so we might need to enable a regulator to bri=
ng
> > > the lines into usable state. Otherwise, this might cause spurious
> > > interrupts and reading from I2C will fail.
> > >=20
> > > Implement support for "vddio-supply" that is enabled by the aw2013
> > > driver
> > > so that the regulator gets enabled when needed.
> > >=20
> > > Signed-off-by: Lin, Meng-Bo <linmengbo0689@protonmail.com>
> > >=20
> > > @@ -348,16 +350,20 @@ static int aw2013_probe(struct i2c_client *clie=
nt)
> > >=20
> > >  		goto error;
> > >  =09
> > >  	}
> > >=20
> > > -	chip->vcc_regulator =3D devm_regulator_get(&client->dev, "vcc");
> > > -	ret =3D PTR_ERR_OR_ZERO(chip->vcc_regulator);
> > > -	if (ret) {
> > > +	chip->regulators[0].supply =3D "vcc";
> > > +	chip->regulators[1].supply =3D "vddio";
> > > +	ret =3D devm_regulator_bulk_get(&client->dev,
> > > +				      ARRAY_SIZE(chip->regulators),
> > > +				      chip->regulators);
> > > +	if (ret < 0) {
> > >=20
> > >  		if (ret !=3D -EPROBE_DEFER)
> > >  	=09
> > >  			dev_err(&client->dev,
> > >  		=09
> > >  				"Failed to request regulator: %d\n",=20
ret);
> > >  	=09
> > >  		goto error;
> >=20
> > Won't this cause failures when optional vddio is unavailable?
>=20
> The regulator core should print a warning "supply vddio not found, using
> dummy regulator" but then proceed normally.
>=20
> I think in almost all cases a separate I/O supply should actually exist
> that could be described in the device tree. It was likely just omitted
> because it's always-on or indirectly being enabled by other devices.
> So perhaps having this warning is even a good thing?

Just briefly jumping in, there was some activity adding bus_regulator to th=
e=20
i2c-core a while back, maybe that can be revived instead? For CCI (camera i=
2c)=20
we also need pull-ups and I don't think adding vddio or whatever to all=20
sensors is a good idea long term...

https://lore.kernel.org/lkml/20210527075556.1709140-1-hsinyi@chromium.org/

Regards
Luca

>=20
> Thanks,
> Stephan