linux-kernel - Re: [PATCH] regulator: qcom-rpmh: Revert "regulator: qcom-rpmh: Use PROBE_FORCE

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Message-ID: <bb5c828a-b8c5-40a0-9b67-44e73abcbef0@sirena.org.uk>
Date:   Wed, 7 Jun 2023 14:18:37 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Amit Pundir <amit.pundir@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Caleb Connolly <caleb.connolly@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regulator: qcom-rpmh: Revert "regulator: qcom-rpmh: Use
 PROBE_FORCE_SYNCHRONOUS"

On Tue, Jun 06, 2023 at 04:29:29PM -0700, Doug Anderson wrote:

> 2. Try adding some delays to some of the regulators with
> "regulator-enable-ramp-delay" and/or "regulator-settling-time-us".
> Without a scope, it'll be tricky to figure out exactly which
> regulators might need delays, but you could at least confirm if the
> "overkill" approach of having all the regulators have some delay
> helps... I guess you could also try putting a big delay for "ldo26".
> If that works, you could try moving it up (again using a bisect style
> approach) to see where the delay matters?

This is information which should be in the datasheets for the part.

> Currently, I guess my mental model of what might be going wrong is
> that regulators are all turning on / adjusting really quickly. Maybe
> they aren't switching into "high power mode" quickly enough, maybe
> they are busy ramping up or down, or maybe there's simply some other
> issue, but I suppose that something happening could be causing the
> voltage to droop down (or be too high) and then that's making RPMH
> upset. Changing the order could be helping avoid this droop, but the
> more proper fix would be to actually account for it with regulator
> constraints.

There could potentially be inrush issues, though I'd not expect
reordering to help much there.

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