linux-kernel - Re: [PATCH] regulator: do not balance regulators without constraints

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Message-ID: <20200528134338.GD3606@sirena.org.uk>
Date:   Thu, 28 May 2020 14:43:38 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Dmitry Osipenko <digetx@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>, peron.clem@...il.com,
        Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        linux-samsung-soc@...r.kernel.org,
        Chanwoo Choi <cw00.choi@...sung.com>
Subject: Re: [PATCH] regulator: do not balance regulators without constraints

On Thu, May 28, 2020 at 03:11:30PM +0200, Marek Szyprowski wrote:

> Balancing coupled regulators must wait until the clients for all of the
> coupled regualtors set their constraints, otherwise the balancing code
> might change the voltage of the not-yet-constrained regulator to the
> value below the bootloader-configured operation point, what might cause a
> system crash.

This forces every supply to have something which explicitly manages
voltages which means that if one of the coupled supplies doesn't really
care about the voltage (perhaps doesn't even have any explicit
consumers) and just needs to be within a certain range of another supply
then it'll end up restricting things needlessly.

Saravana was trying to do some stuff with sync_state() which might be
interesting here although I have concerns with that approach too:

   https://lore.kernel.org/lkml/20200527074057.246606-1-saravanak@google.com/

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