linux-kernel - Re: [RFC 3/5] regulator: core: Only apply constraints if available on list voltage

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Message-ID: <20140729171857.GV17528@sirena.org.uk>
Date:	Tue, 29 Jul 2014 18:18:57 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Kukjin Kim <kgene.kim@...sung.com>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Yuvaraj Kumar C D <yuvaraj.cd@...il.com>,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 3/5] regulator: core: Only apply constraints if available
 on list voltage

On Tue, Jul 29, 2014 at 06:28:57PM +0200, Javier Martinez Canillas wrote:
> If a selector can't be used on a platform due to voltage constraints,
> regulator_list_voltage() returns 0. Doing this unconditionally made
> sense since constraints were set in machine_constraints_voltage() at
> regulator registration time.
> 
> But for load switches that don't define a voltage output, the parent
> supply voltage is used so the constraints should only be applied if
> they were defined for the child regulators.

No, think about what you're doing here and why we're filtering out
unsettable voltages - this causes problems for consumers on regulators
that don't have any ability to vary voltages since they will now be able
to list voltages that they can't select.  

I would also expect any regulator where the supplied devices are able to
vary the voltage to explicitly provide a constraint even if the
implementation is done in a parent regulator.  There may be constraints
on the child supply which aren't directly present on the parent supply
and can be ignored if the child supply is turned off.

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