linux-kernel - Re: [PATCH v7] regulator: fixed: Convert to use GPIO descriptor only

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Date:   Fri, 12 Oct 2018 11:43:13 +0000
From:   Marcel Ziswiler <marcel.ziswiler@...adex.com>
To:     "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "jonathanh@...dia.com" <jonathanh@...dia.com>
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Subject: Re: [PATCH v7] regulator: fixed: Convert to use GPIO descriptor only

On Fri, 2018-10-12 at 11:43 +0100, Russell King - ARM Linux wrote:
> On Fri, Oct 12, 2018 at 11:39:15AM +0100, Jon Hunter wrote:
> > We had the same situation for Tegra124 Jetson TK1 but I don't think
> > that
> > adding a pseudo intermediate regulator is cleaner. If the GPIO
> > controls
> > more than one regulator, I don't see why is it necessary to change
> > the
> > DT. There are several other people reporting the same problem with
> > various different boards. So this does seem to be a common usage.
> 
> Given that DT describes the hardware, not the software
> implementation,
> it must not change just because we move from GPIO numbers to GPIO
> descriptors.

Yes, that I do agree. However, like mentioned before on quick glance I
really could not find any documentation about this "GPIO sharing" being
allowed or not.

> The existing DT description is reasonable, and introducing ficticious
> regulators in DT to work around the implementation is not reasonable.

I don't think it is that fictitious as it makes it crystal clear that
there is something shared with all its pros and cons. E.g. what happens
if one of them regulators wants to turn off while the other one still
needs power? The regular regulator dependency tree would nicely make
this all clear.