linux-kernel - Re: RFC power domain vs generic supply regulator

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Date:   Thu, 5 Aug 2021 19:39:42 +0200
From:   Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: RFC power domain vs generic supply regulator

Hi Mark

On Thu, Aug 5, 2021 at 7:23 PM Mark Brown <broonie@...nel.org> wrote:
>
> On Tue, Jun 08, 2021 at 08:01:20AM +0200, Michael Nazzareno Trimarchi wrote:
>
> > I'm trying to understand how to deal with devices that do not provide
> > a supply handle connection using the device tree, or if there is a
> > generic way
> > to connect to a regulator. The pinctrl has a generic binding inside
> > dd.c that allow to mux pinout during probing or it allows to define a
> > power domain,
> > According to the code I read the power domain can be only connected to
> > the SoC power domain but in general a generic power domain can be
> > connected
> > to any source aka a regulator. For example and spi-nor can be powered
> > but a gpio regulator or any kind of supply connection and bunch of
> > devices
> > can just need a supply if they are probed or binded runtime. Can
> > someone give me feedback on this topic?
>
> I'm having a really hard time parsing the issue you're trying to solve
> here.  Power domains and regulators are different things, power domains
> represent blocks with a SoC which have some kind of power control which
> may involve a combination of things, the drivers for the devices within
> those domains generally just do runtime PM and then let the driver core
> figure out what's going on with them.  Regulators are for things with
> physical supplies that can be seen in the schematic for the board, in
> general anything that uses a regulator should explicitly say so in its
> binding - supporting some sort of generic mapping isn't great since it
> means that we don't have any control over which regulator is which and
> that makes it hard to add control of the regulators later.  Power
> domanis may possibly have regulators among the resources they use but
> that would just be a normal device binding for the power domain.  All of
> this is orthogonal to when drivers for devices get loaded, that can
> happen at any point while the system is running and doesn't really
> affect how the relationships are described.

So in short you said that if I have a device that has no definition of
supply in his
documentation, this device needs to support the supply in his binding
and make to sense
to create something like:

generic-supply = <&regulator_device>;

and let dd to pick them up

Michael




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Michael Nazzareno Trimarchi
Co-Founder & Chief Executive Officer
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michael@...rulasolutions.com
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