linux-kernel - Re: [PATCH V4 1/6] dt-bindings: regulator: Add "regulator-min-dropout-voltage-microvolt"

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Message-ID: <Ya5VhkggWdjYyTHL@sirena.org.uk>
Date:   Mon, 6 Dec 2021 18:25:10 +0000
From:   Mark Brown <broonie@...nel.org>
To:     "Satya Priya Kakitapalli (Temp)" <quic_c_skakit@...cinc.com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>, swboyd@...omium.org,
        collinsd@...eaurora.org, subbaram@...eaurora.org,
        Das Srinagesh <gurus@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 1/6] dt-bindings: regulator: Add
 "regulator-min-dropout-voltage-microvolt"

On Mon, Dec 06, 2021 at 06:33:26PM +0530, Satya Priya Kakitapalli (Temp) wrote:
> On 11/25/2021 8:47 PM, Mark Brown wrote:

> > Usually this is a fixed property of the regulator rather than something
> > that varies per board - why have a DT property?

> The min-dropout value (headroom) varies with boards, that's why we have a DT
> property for it. We overwrite the default value in driver with actual value
> read from DT

Interesting.  How exactly does that end up happening - presumably other
systems are going to run into it?

If you do have board designs which somehow managed to introduce
additional dropouts (seems pretty concerning TBH) then I think the best
way to handle that is to add a generic property for it and have that
either added on to or override the requirements of the regulator itself
which should continue to be defined in the driver.  That way only boards
with issues need to do anything which will avoid bugs with the property
being omitted in what should be the common case.

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