linux-kernel - Re: [PATCH v2 05/11] mfd: devicetree: bindings: Add Qualcomm SMD based RPM DT binding

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Date:	Mon, 27 Jul 2015 08:29:18 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Bjorn Andersson <bjorn.andersson@...ymobile.com>,
	"bjorn@...o.se" <bjorn@...o.se>,
	Andy Gross <agross@...eaurora.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v2 05/11] mfd: devicetree: bindings: Add Qualcomm SMD
 based RPM DT binding

On Fri, 24 Jul 2015, Mark Brown wrote:

> On Fri, Jul 24, 2015 at 11:24:34AM +0100, Mark Brown wrote:
> > On Fri, Jul 24, 2015 at 10:58:47AM +0100, Lee Jones wrote:
> > > On Thu, 23 Jul 2015, Mark Brown wrote:
> 
> > > > I have no idea what's going on here, sorry.  I've not been reading this
> > > > thread.
> 
> > > All of the information you need is in the email you replied to.
> 
> > The mail appears to have an edited down section of what looks like an
> > example rather than the actual binding.  I haven't seen the binding so I
> > can't really comment on it.
> 
> I managed to find the binding but I'm afraid I'm still not sure what the
> concern here is - can someone please be specific about the question(s)
> you're looking for an answer on?

[...]

>From here:

> > > > > +                pm8941-regulators {
> > > > > +                        compatible = "qcom,rpm-pm8941-regulators";
> > > > > +                        vdd_l13_l20_l23_l24-supply = <&pm8941_boost>;
> > > > 
> > > > I'd like Mark to glance at this.

Mark: Is this new property okay?

> > > > > +                        pm8941_s3: s3 {
> > > > > +                                regulator-min-microvolt = <1800000>;
> > > > > +                                regulator-max-microvolt = <1800000>;
> > > > 
> > > > Aren't these fixed regulators?
> > > 
> > > In this system configuration most of the regulators have fixed values,
> > > but the regulators (hw) are not fixed.
> >
> > I'm not sure that's how it works.  I believe 'max' and 'min' should
> > describe the upper and lower constraints of the regulator.  The actual
> > value it runs it is selected elsewhere.
> 
> The specified range of the regulator is 1.75-1.85V and this is handled
> by the implementation, however the board designers have stated that it
> is only allowed to be configured to 1.8V.
> 
> So DT is used to narrow the capabilities of the individual component to
> something that's suitable for this particular system.
> 
> > We still need Mark to look at this.

Is it okay for the regulator-{min,max}-microvolt to be artificially
restricted to the required value, despite knowing that the regulator
is capable of supply {more,less} voltage?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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