linux-kernel - Re: [RFC 5/8] regulator: anatop: fix min dropout for bypass mode

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Message-ID: <20170324125438.5wy3r2mr3g5eaxvy@sirena.org.uk>
Date:   Fri, 24 Mar 2017 12:54:38 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Leonard Crestez <leonard.crestez@....com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Robin Gong <yibin.gong@....com>,
        Anson Huang <Anson.Huang@....com>,
        Irina Tirdea <irina.tirdea@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        Octavian Purdila <octavian.purdila@....com>,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 5/8] regulator: anatop: fix min dropout for bypass mode

On Wed, Mar 22, 2017 at 06:53:07PM +0200, Leonard Crestez wrote:

> +	if (anatop_reg->bypass)
> +		anatop_reg->rdesc.min_dropout_uV = 0;
> +	else
> +		anatop_reg->rdesc.min_dropout_uV = LDO_MIN_DROPOUT_UV;

No, this is completely broken - you can't expect to randomly change hthe
regulator description at runtime behind the back of the framework and
expect things to work.  If there is a need to do this we need an
interface for getting the current value and a way to notify of changes.

That said I would not expect the dropout voltage to be considered at
all when the regulator is bypassed, since the regulator is not
regulating it doesn't need any headroom.

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