linux-kernel - Re: [PATCH] regulator: core: Skip balancing of the enabled regulators in regulator

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Message-ID: <439154a4-1502-40af-7086-d4e3eb24025f@gmail.com>
Date:   Tue, 8 Oct 2019 21:00:29 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-samsung-soc@...r.kernel.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Kamil Konieczny <k.konieczny@...sung.com>
Subject: Re: [PATCH] regulator: core: Skip balancing of the enabled regulators
 in regulator_enable()

08.10.2019 20:17, Mark Brown пишет:
> On Tue, Oct 08, 2019 at 08:05:03PM +0300, Dmitry Osipenko wrote:
>> 08.10.2019 19:15, Mark Brown пишет:
> 
>>> That sounds like it might just postpone the inevitable - if you set the
>>> wrong voltage first it might decide to drop down some voltage that
>>> wasn't expected.  There's a bit of a bootstrapping issue.  I think it
>>> would be safer to just say that anything that is within spec won't get
>>> changed any time we balance, we'd only change things if needed to bring
>>> them back into spec.
> 
>> Yes, the case of changing voltage before regulator is enabled seems
>> won't work as expected.
> 
>> Maybe it won't hurt to disallow a non always-on regulators to be coupled
>> until there will be a real user for that case.
> 
> I thought that coupling with the CPU core and main SoC power regulators
> was one of the main use cases for this feature?
> 

In a case of NVIDIA Tegra SoCs, it's coupling of CPU core *and* SoC core
regulators. I see that Exynos also couples the always-on regulators.

Properly handling case of a disabled coupled regulator certainly will be
useful, but looks like there are no real users for that feature right
now and thus no real testing is done.

Keeping coupled regulators in s valid voltage range is the today's main
feature.