linux-kernel - Re: [RFC PATCH] regulator: core: allow consumers to request to closes step voltage

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Message-ID: <20130621143018.GT27646@sirena.org.uk>
Date:	Fri, 21 Jun 2013 15:30:18 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Nishanth Menon <nm@...com>
Cc:	Liam Girdwood <lgirdwood@...il.com>, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, viresh.kumar@...aro.org,
	cpufreq@...r.kernel.org
Subject: Re: [RFC PATCH] regulator: core: allow consumers to request to
 closes step voltage

On Fri, Jun 21, 2013 at 07:43:55AM -0500, Nishanth Menon wrote:
> On 10:51-20130621, Mark Brown wrote:

> > No, the consumer really doesn't want to be aware of linear step
> > regulators.  Why would it care that there even are linear steps?  If
> > the consumer is doing this based on the properties of the regulator
> > rather than on the properties of the consumer this indicates that the
> > consumer has a problem  If the consumer is doing this based on the
> > properties of the regulator rather than on the properties of the
> > consumer this indicates that the consumer has a problem

> The specific case that I am trying to tackle is as follows:
> cpufreq-cpu0 uses definitions of voltages that are SoC specific. For a
> given frequency, the optimal voltage is X, max voltage(Y) is already
> expected to be in constraints for device functionality. We however want
> to find the closest voltage for a regulator in range X to Y best
> achievable by regulator. I think the area where I am getting confused is
> this: I am thinking the job belongs to the consumer/regulator core to
> find the best match. However, looking at implementations in existing
> regulators and based on your explanation, it seems to be the job of
> the regulator driver rather than the consumer/ regulator core to provide
> the best match.

Right, though the consumer does have to provide a voltage range to the
regulator to allow this to happen - if the consumer doesn't provide a
range then there's only one option available.  The consumer provides a
range and then the driver satistifes that as best it can (after it's
been filtered through the constraints).

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