linux-kernel - Re: [PATCH v4 4/4] regulator: Prevent falling too fast

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Message-ID: <20161214132108.3d36vuxpcrc2b7v2@sirena.org.uk>
Date:   Wed, 14 Dec 2016 13:21:08 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Matthias Kaehlcke <mka@...omium.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Brian Norris <briannorris@...omium.org>,
        Javier Martinez Canillas <javier@...hile0.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 4/4] regulator: Prevent falling too fast

On Tue, Dec 13, 2016 at 12:00:32PM -0800, Doug Anderson wrote:
> On Tue, Dec 13, 2016 at 9:19 AM, Mark Brown <broonie@...nel.org> wrote:

> > No, not unless the prior descriptions of the hardware have been wildly
> > inaccurate - my understanding had been that the DCDC was a normal DCDC
> > with an analogue input intended to be biased to set the output voltage
> > (presumably in terms of a full rail supply) and that the PWM had been
> > connected to this analogue input.  If the PWM is supplying the DCDC then
> > the hardware design just seems bizzare, I can't see how this would even
> > work.

> As you can see from the datasheet ("Adjusting the Output Voltage"
> section), it is intended that you stuff a resistor to make a voltage
> divider and that's how you select the output voltage.  In our case the

OK, that's what I thought was happening.  That's definitely something
that should *not* end up in ->supply, that should hold the parent supply
that the DCDC is regulating down to the target voltage.

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