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

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Message-ID: <20161213171904.ohsxc3xhscdinctt@sirena.org.uk>
Date:   Tue, 13 Dec 2016 17:19:04 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Doug Anderson <dianders@...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 Mon, Dec 12, 2016 at 01:15:02PM -0800, Matthias Kaehlcke wrote:
> El Fri, Oct 28, 2016 at 07:15:21PM +0100 Mark Brown ha dit:
> > On Mon, Sep 26, 2016 at 10:41:59AM -0700, Doug Anderson wrote:

> > What you're describing to me is a discrete DCDC that has an input
> > voltage that sets the output voltage which happens to be set with a PWM.

> I experimented a bit with this. Besides the question of how to model
> the passives I wonder how the two regulators would interact. The
> correct thing seems to be to specify the input regulator as a supply
> of the DCDC. dcdc->set_voltage breaks down a voltage transition into

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.

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