linux-kernel - Re: [PATCH v2 2/2] leds: aw2013: Add vddio regulator

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Message-ID: <2672233.mvXUDI8C0e@z3ntu.xyz>
Date:   Wed, 29 Mar 2023 18:54:54 +0200
From:   Luca Weiss <luca@...tu.xyz>
To:     Pavel Machek <pavel@....cz>, ~postmarketos/upstreaming@...ts.sr.ht
Cc:     "Lin, Meng-Bo" <linmengbo0689@...tonmail.com>,
        linux-kernel@...r.kernel.org, Lee Jones <lee@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Nikita Travkin <nikita@...n.ru>, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        Stephan Gerhold <stephan@...hold.net>
Subject: Re: [PATCH v2 2/2] leds: aw2013: Add vddio regulator

On Freitag, 24. März 2023 09:32:52 CEST Stephan Gerhold wrote:
> Hi Pavel,
> 
> 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 bring
> > > the lines into usable state. Otherwise, this might cause spurious
> > > interrupts and reading from I2C will fail.
> > > 
> > > Implement support for "vddio-supply" that is enabled by the aw2013
> > > driver
> > > so that the regulator gets enabled when needed.
> > > 
> > > Signed-off-by: Lin, Meng-Bo <linmengbo0689@...tonmail.com>
> > > 
> > > @@ -348,16 +350,20 @@ static int aw2013_probe(struct i2c_client *client)
> > > 
> > >  		goto error;
> > >  	
> > >  	}
> > > 
> > > -	chip->vcc_regulator = devm_regulator_get(&client->dev, "vcc");
> > > -	ret = PTR_ERR_OR_ZERO(chip->vcc_regulator);
> > > -	if (ret) {
> > > +	chip->regulators[0].supply = "vcc";
> > > +	chip->regulators[1].supply = "vddio";
> > > +	ret = devm_regulator_bulk_get(&client->dev,
> > > +				      ARRAY_SIZE(chip->regulators),
> > > +				      chip->regulators);
> > > +	if (ret < 0) {
> > > 
> > >  		if (ret != -EPROBE_DEFER)
> > >  		
> > >  			dev_err(&client->dev,
> > >  			
> > >  				"Failed to request regulator: %d\n", 
ret);
> > >  		
> > >  		goto error;
> > 
> > Won't this cause failures when optional vddio is unavailable?
> 
> The regulator core should print a warning "supply vddio not found, using
> dummy regulator" but then proceed normally.
> 
> 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 the 
i2c-core a while back, maybe that can be revived instead? For CCI (camera i2c) 
we also need pull-ups and I don't think adding vddio or whatever to all 
sensors is a good idea long term...

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

Regards
Luca

> 
> Thanks,
> Stephan