linux-kernel - Re: [PATCH] usb: phy: generic: request regulator optionally

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Date:   Tue, 06 Sep 2016 11:01:15 -0700
From:   Stefan Agner <stefan@...er.ch>
To:     Mark Brown <broonie@...nel.org>
Cc:     Felipe Balbi <balbi@...nel.org>, gregkh@...uxfoundation.org,
        fabio.estevam@....com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: phy: generic: request regulator optionally

On 2016-09-06 01:22, Mark Brown wrote:
> On Tue, Sep 06, 2016 at 10:45:19AM +0300, Felipe Balbi wrote:
>> Stefan Agner <stefan@...er.ch> writes:
> 
>> > According to the device tree bindings the vcc-supply is optional.
> 
> This is nonsense unless the device can work without this supply.  Given
> that the supply is called VCC that doesn't seem entirely likely.

Afaik it is kind of a generic device tree binding, I guess the physical
device can have various appearances and properties...

A quick survey showed several device trees which do not specify
vcc-supply...

That said, I checked the device at hand, and it actually has a USB PHY
power supply inputs, but the device tree does not model them.

>> > +	nop->vcc = devm_regulator_get_optional(dev, "vcc");
>> >  	if (IS_ERR(nop->vcc)) {
>> >  		dev_dbg(dev, "Error getting vcc regulator: %ld\n",
>> >  					PTR_ERR(nop->vcc));
>> > -		if (needs_vcc)
>> > -			return -EPROBE_DEFER;
>> > +		if (needs_vcc || PTR_ERR(nop->vcc) == -EPROBE_DEFER)
>> > +			return PTR_ERR(nop->vcc);
> 
>> does this look okay from a regulator API perspective?
> 
> That's how to use _get_optional() but it's really unusual that you
> should be using _get_optional().

Despite the above findings, I still think it is the right thing to do as
long as we specify vcc-supply to be optional.

--
Stefan