linux-kernel - Re: [PATCH 1/2] regulator: DT: Add support to scale ramp delay based on platform behavior

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Message-ID: <20160301022326.GC18327@sirena.org.uk>
Date:	Tue, 1 Mar 2016 11:23:26 +0900
From:	Mark Brown <broonie@...nel.org>
To:	Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:	Laxman Dewangan <ldewangan@...dia.com>, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, lgirdwood@...il.com,
	bjorn.andersson@...ymobile.com, swarren@...dotorg.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] regulator: DT: Add support to scale ramp delay based
 on platform behavior

On Mon, Feb 29, 2016 at 09:47:51AM -0800, Bjorn Andersson wrote:
> On Mon 29 Feb 06:40 PST 2016, Laxman Dewangan wrote:

> > It is observed that voltage change in given rail affected by the load
> > and the capacitor in the rail. This may cause the slow ramp in voltage
> > against what PMIC has programmed.

> The regulator-ramp-delay is a variable you can tweak on a board basis,
> so I'm not sure what benefit it gives to be able to add a scaling
> factor to this.

> In my experience your HW engineer will say "you have to wait X ms", not
> "you have to wait 125% of X ms".

> Can you please elaborate on why the original knob isn't sufficient?

Right, this definitely feels like the wrong thing is being specified
here (and also like the PMIC might be going out of spec, possibly as a
result of being overloaded) and that the existing board specific
controls should be used.  It just doesn't correspond to the way people
usually talk about specs for PMICs.

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