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

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Date:   Wed, 14 Jun 2023 08:50:16 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Linux regressions mailing list <regressions@...ts.linux.dev>
Cc:     Mark Brown <broonie@...nel.org>,
        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"

Hi,

On Wed, Jun 14, 2023 at 8:37 AM Linux regression tracking (Thorsten
Leemhuis) <regressions@...mhuis.info> wrote:
>
> Hi, Thorsten here, the Linux kernel's regression tracker.
>
> On 07.06.23 15:47, Doug Anderson wrote:
> >
> > On Wed, Jun 7, 2023 at 6:18 AM Mark Brown <broonie@...nel.org> wrote:
> >>
> >> 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.
> >
> > I was thinking more of something board-specific, not part specific. In
> > theory with RPMH this is also all supposed to be abstracted out into
> > the firmware code that sets up RPMH which magically takes care of
> > things like this, but it certainly could be wrong.
>
> /me waves friendly
>
> That afaics was the last mail in this thread about a regression caused
> by ad44ac082fd ("regulator: qcom-rpmh: Revert "regulator: qcom-rpmh: Use
> PROBE_FORCE_SYNCHRONOUS"") from Doug; Amit's attempt to patch it (
> https://lore.kernel.org/lkml/20230602161246.1855448-1-amit.pundir@linaro.org/
> ) also wasn't welcomed. Just like his earlier revert attempt
> (https://lore.kernel.org/lkml/20230515145323.1693044-1-amit.pundir@linaro.org/
> ).
>
> Does this mean this regression won't be addressed before 6.4 is
> released? Or was there some progress and I just missed it? What should I
> tell Linus in my next report?

Of the two proposals made (the revert vs. the reordering of the dts),
the reordering of the dts seems better. It only affects the one buggy
board (rather than preventing us to move to async probe for everyone)
and it also has a chance of actually fixing something (changing the
order that regulators probe in rpmh-regulator might legitimately work
around the problem). That being said, just like the revert the dts
reordering is still just papering over the problem and is fragile /
not guaranteed to work forever.

-Doug