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

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Message-ID: <86b9b4b5-cca5-9052-7c87-c5679dfffff4@samsung.com>
Date:   Tue, 8 Oct 2019 15:24:17 +0200
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Mark Brown <broonie@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     linux-kernel@...r.kernel.org, Dmitry Osipenko <digetx@...il.com>,
        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()


On 10/8/19 2:47 PM, Mark Brown wrote:
> On Tue, Oct 08, 2019 at 02:38:55PM +0200, Marek Szyprowski wrote:
> 
>> Then if I get it right, the issue is caused by the commit 7f93ff73f7c8 
>> ("opp: core: add regulators enable and disable"). I've checked and 
>> indeed reverting it fixes Peach Pi to boot properly. The question is if 
>> this is desired behavior or not?
> 
> That doesn't seem ideal - either it's redundant for regulators that need
> to be marked as always-on anyway or it's going to force the regulators
> on when a device could do runtime PM (eg, if the same code can run on
> something like a GPU which can be turned off while the screen is off or
> is displaying a static image).

Commit 7f93ff73f7c8 ("opp: core: add regulators enable and disable")
currently can be safely reverted as all affected users use always-on
regulators. However IMHO it should be possible to enable always-on
regulator without side-effects.

When it comes to setting regulator constraints before doing enable
operation, it also seems to be possible solution but would require
splitting regulator_set_voltage() operation on two functions:

- one for setting constraints (before regulator_enable() operation)

- the other one actually setting voltage (after enable operation)

Unfortunately this is much bigger task and doesn't seem to be -rc
time material so I'm in favor of just applying Marek's fix as it is
for now.
 
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics