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

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Date:   Fri, 17 Apr 2020 14:33:14 +0200
From:   Clément Péron <peron.clem@...il.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Steven Price <steven.price@....com>,
        Mark Brown <broonie@...nel.org>, 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>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>
Subject: Re: Multiple regulators for one device [was drm/panfrost: add devfreq
 regulator support]

Hi Robin,

On Fri, 17 Apr 2020 at 13:10, Robin Murphy <robin.murphy@....com> wrote:
>
> On 2020-04-16 2:42 pm, Steven Price wrote:
> [...]
> > Perhaps a better approach would be for Panfrost to hand over the struct
> > regulator objects it has already got to the OPP framework. I.e. open
> > code dev_pm_opp_set_regulators(), but instead of calling
> > regulator_get_optional() simply populate the regulators we already have?
> >
> > The other benefit of that is it would provide a clear hand-over of
> > responsibility between Panfrost handling it's own regulators and the OPP
> > framework picking up the work. The disadvantage is that Panfrost would
> > have to track whether the regulators have been handed over or not.
>
> Sounds like the most logical thing to do is to shuffle things around so
> we start by trying to set up an OPP table, then fall back to explicitly
> claiming clocks and regulators if necessary. Then we can easily make the
> devfreq decision later in probe based on how that turned out.

Ok I will propose a new serie with this behavior,

Thanks
Clement

>
> Robin.