linux-kernel - Re: [RFC v2 5/6] drivers: boot_constraint: Add initial DT bindings

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Date:   Thu, 13 Jul 2017 15:06:08 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Shiraz Hashim <shashim@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [RFC v2 5/6] drivers: boot_constraint: Add initial DT bindings

On 12-07-17, 16:28, Rob Herring wrote:
> Display is a pretty well known use case here. Do you have other
> examples in mind?

No, I don't.

@Stephen: Do you have more cases like this for your Qcom products ?

> Other cases I've seen are automotive with keeping
> the backup camera going and CAN bus handling. Though my new car has a
> flicker shortly after coming on, so I guess the handoff doesn't have
> to be completely seemless. :)

:)

> [...]
> 
> > +       mmc: mmc@0x0 {
> > +               ...
> > +               ...
> > +               vmmc-supply = <&twl_reg1>;
> > +               vmmcaux-supply = <&twl_reg2>;
> > +               boot-constraint-supplies = "vmmc", "vmmcaux";
> > +               boot-constraint-uV = <1800000 2000000>, /* vmmc */
> > +                                    <2000000 2000000>; /* vmmcaux */
> 
> No. I don't like how this is going to extend to all the other bindings
> people are going to want constraints for. We don't need a parallel set
> of properties for each type of binding.

Fair enough.

> I'm not convinced that we need a general solution for what's probably
> a handful of things that need a handoff versus just re-initialize.

What about keeping the first four patches (mostly) as it is and adding
these constraints from a platform specific constraints driver ?

Will that be acceptable ?

-- 
viresh