linux-kernel - Re: Multiple regulators for one device [was drm/panfrost: add devfreq regulator support]

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Message-ID: <20200416140434.GL5354@sirena.org.uk>
Date:   Thu, 16 Apr 2020 15:04:34 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Steven Price <steven.price@....com>
Cc:     Clément Péron <peron.clem@...il.com>,
        Nishanth Menon <nm@...com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Multiple regulators for one device [was drm/panfrost: add
 devfreq regulator support]

On Thu, Apr 16, 2020 at 02:42:13PM +0100, Steven Price wrote:
> On 14/04/2020 20:16, Clément Péron wrote:

> > That's can be reworked and Panfrost can only probe regulator if there
> > is no opp-table.

> This is what I was thinking about looking at. But it may make sense instead
> to extend the regulator API to allow multiple regualtor_get() calls for a
> single device. I haven't had time to dig into how difficult this would be.

To repeat what I said before we don't actively stop this, it's just not
something that seems particularly tasteful and the warning does find
actual errors.  I definitely don't think it's a good idea to extend the
API for this.

> Ideally calling regulator_get a second time for the same device would simply
> return the same struct regulator object (with a reference count increment).

One of the goals with the distinct struct regulator is to make sure that
we track all the user's activity together - if we mix multiple users in
there it becomes harder to tell if something is going wrong.

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