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

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Message-ID: <5290a7a8-2a0a-cb89-9d62-270393123054@arm.com>
Date:   Fri, 17 Apr 2020 12:10:18 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Steven Price <steven.price@....com>,
        Clément Péron <peron.clem@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     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]

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.

Robin.