linux-kernel - Re: [PATCH] regulator: Provide a check for dummy regulator

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Message-ID: <20120420130134.GA5957@opensource.wolfsonmicro.com>
Date:	Fri, 20 Apr 2012 14:01:34 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Jassi Brar <jaswinder.singh@...aro.org>
Cc:	linux-kernel@...r.kernel.org, lrg@...com
Subject: Re: [PATCH] regulator: Provide a check for dummy regulator

On Fri, Apr 20, 2012 at 05:59:42PM +0530, Jassi Brar wrote:

> That's what I have been trying to fix. My example might be fictitious but
> I have a real scenario with omap_hsmmc (I was avoiding getting into that).

> The dummy not just provide a place holder data structure for missing definition
> of an available supply, but it also masks the fact that there might indeed be no
> supply at all on the given machine.

> As I said, atm the only option for a consumer is to know it via PD/DT.

No.  You're failing to understand what dummy regulators are for.  To
repeat yet again you're not supposed to actually use dummy regulators,
you're supposed to fully specify the regulators on your platform.  As
I've said several times now dummy regulators are just a crutch to hold
systems together, if they're not working out the solution is to turn
them off and even if they are working out turning them off is still the
best thing to do.  The problems you are seeing are exactly why this is
the case.

> The benefit is magnified by the fact that, for a given circuit, at
> least theoretically,
> there is no limit to the number/combination of supplies that could be controlled
> by inserting a regulator. And that could lead to a very noisy PD/DT.

No, any given circuit is going to have a very clear set of things that
can be controlled by a regulator, and most chips have a fixed set of
supplies they always need so it's very simple from their point of view.

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