linux-kernel - Re: [PATCH v2 1/3] dt-binding: power: Add otg regulator binding

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Message-ID: <20151209195915.GJ4000@usrtlx11787.corpusers.net>
Date:	Wed, 9 Dec 2015 11:59:15 -0800
From:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
To:	Rob Herring <robh@...nel.org>
CC:	"Bird, Tim" <Tim.Bird@...ymobile.com>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"sre@...nel.org" <sre@...nel.org>,
	"dbaryshkov@...il.com" <dbaryshkov@...il.com>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"agross@...eaurora.org" <agross@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tbird20d@...il.com" <tbird20d@...il.com>,
	"Cavin, Courtney" <Courtney.Cavin@...ymobile.com>
Subject: Re: [PATCH v2 1/3] dt-binding: power: Add otg regulator binding

On Wed 09 Dec 06:36 PST 2015, Rob Herring wrote:

> On Wed, Dec 9, 2015 at 6:55 AM, Tim Bird <tim.bird@...ymobile.com> wrote:
> > On 12/08/2015 08:11 PM, Rob Herring wrote:
> >> On Tue, Dec 08, 2015 at 04:40:16PM -0800, Tim Bird wrote:
> >>> Add a binding for the regulator which controls the OTG chargepath switch.
> >>> The OTG switch gets its power from pm8941_5vs1, and that should be
> >>> expressed as a usb-otg-in-supply property in the DT node for the
> >>> charger driver.  The regulator name is "otg".
> 
> [...]
> 
> >>> +child nodes:
> >>> +- otg:
> >>> +  Usage: optional
> >>> +  Description: This node defines a regulator used to control the direction
> >>> +               of VBUS voltage - specifically: whether to supply voltage
> >>> +               to VBUS for host mode operation of the OTG port, or allow
> >>> +               input voltage from external VBUS for charging.  In the
> >>> +               hardware, the supply for this regulator comes from
> >>> +               usb-otg-in-supply.
> >>
> >> Doesn't this regulator need to have a name defined?
> >
> > I'm not sure what you mean.  The regulator name is "otg", defined by the DT node
> > name. The code requires that the DT node name be "otg", and defines a regulator
> > with the same name.
> >
> > As far as I know, you have to define a DT label for the node, in order
> > to reference this regulator with a phandle.  Is that what you are referring to?
> > I usually use "chg_otg" as the label.  Are you asking that this be reflected
> > in the example?
> 
> You need a regulator-name property. Also, should should define valid
> values for regulator-min-microvolt and regulator-max-microvolt.
> 

The regulator has a name, derived from the node name, and this is
significant. If the developer wants an additional human readable name
for some reason they can use the optional regulator-name property.

The regulator is a simple switch and as such inherits voltage properties
from its supply. It should therefor not have any specified voltage
range.

> Thinking about this some more, the node name should be generic, so
> just "regulator". The label does not need to be generic.
> 

The name of the node is significant, as it's used for matching the
regulator to an implementation.

Regards,
Bjorn
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