linux-kernel - Re: [PATCH v3 01/11] regulator: core: add API to get voltage constraints

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Message-ID: <20180207152045.GC5850@tbergstrom-lnx.Nvidia.com>
Date:   Wed, 7 Feb 2018 17:20:45 +0200
From:   Peter De Schrijver <pdeschrijver@...dia.com>
To:     Mark Brown <broonie@...nel.org>
CC:     <linux-tegra@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <mturquette@...libre.com>, <sboyd@...eaurora.org>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <devicetree@...r.kernel.org>, <lgirdwood@...il.com>,
        <linux-kernel@...r.kernel.org>,
        Laxman Dewangan <ldewangan@...dia.com>
Subject: Re: [PATCH v3 01/11] regulator: core: add API to get voltage
 constraints

On Wed, Feb 07, 2018 at 03:01:55PM +0000, Mark Brown wrote:
> On Wed, Feb 07, 2018 at 04:32:13PM +0200, Peter De Schrijver wrote:
> > On Wed, Feb 07, 2018 at 02:18:46PM +0000, Mark Brown wrote:
> 
> > > You're going to have to provide a much better explanation of what this
> > > is doing - right now it seems like an abuse of constraints.  Client
> > > drivers can already determine if a particular voltage they want to set
> > > is available via regulator_list_voltage() and so on, that's what
> > > constraints are there to set.  It sounds like you're trying to use them
> > > for something else but you're really not explaining your use case
> > > clearly.
> 
> > There is no way to query what voltage I will actually get for a given input
> 
> I looked at patch 2.  It looked like an abuse of what constraints do,
> and had zero explanation of why it was doing what it was doing.  In any
> case we need the regulator code and changelog to be clear about what the
> interface is for and why it should be used, that's not happening here.
> 
> > voltage. If you read drivers/clk/tegra/cvb. (you did do that right?), you
> > will see that there is a minimum and maximum voltage defined by
> > charaterization which needs to be capped to the regulator generated voltages
> > for those points.
> 
> I can't really tell what you're saying here.  If the driver needs to
> know if it can set the a given voltage there's already an API for doing
> that as I said.  If you're trying to convey this minimum and maximum
> voltage via the constraints that sounds like an abuse of the constraints.


No, what I want is the voltage which the regulator will output for a given
regulator_set_voltage request taking constraints, regulator step etc into
account.

Peter.