linux-kernel - Re: [PATCH] arm64: dts: qcom: sdm845-db845c: Move LVS regulator nodes up

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Date:   Thu, 15 Jun 2023 19:17:02 +0530
From:   Amit Pundir <amit.pundir@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Linux regressions mailing list <regressions@...ts.linux.dev>,
        Mark Brown <broonie@...nel.org>,
        Doug Anderson <dianders@...omium.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Caleb Connolly <caleb.connolly@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dt <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: sdm845-db845c: Move LVS regulator nodes up

On Thu, 15 Jun 2023 at 00:38, Amit Pundir <amit.pundir@...aro.org> wrote:
>
> On Thu, 15 Jun 2023 at 00:17, Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
> >
> > On 14/06/2023 20:18, Linux regression tracking (Thorsten Leemhuis) wrote:
> > > On 02.06.23 18:12, Amit Pundir wrote:
> > >> Move lvs1 and lvs2 regulator nodes up in the rpmh-regulators
> > >> list to workaround a boot regression uncovered by the upstream
> > >> commit ad44ac082fdf ("regulator: qcom-rpmh: Revert "regulator:
> > >> qcom-rpmh: Use PROBE_FORCE_SYNCHRONOUS"").
> > >>
> > >> Without this fix DB845c fail to boot at times because one of the
> > >> lvs1 or lvs2 regulators fail to turn ON in time.
> > >
> > > /me waves friendly
> > >
> > > FWIW, as it's not obvious: this...
> > >
> > >> Link: https://lore.kernel.org/all/CAMi1Hd1avQDcDQf137m2auz2znov4XL8YGrLZsw5edb-NtRJRw@mail.gmail.com/
> > >
> > > ...is a report about a regression. One that we could still solve before
> > > 6.4 is out. One I'll likely will point Linus to, unless a fix comes into
> > > sight.
> > >
> > > When I noticed the reluctant replies to this patch I earlier today asked
> > > in the thread with the report what the plan forward was:
> > > https://lore.kernel.org/all/CAD%3DFV%3DV-h4EUKHCM9UivsFHRsJPY5sAiwXV3a1hUX9DUMkkxdg@mail.gmail.com/
> > >
> > > Dough there replied:
> > >
> > > ```
> > > 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.
> > > ```
> > >
> > > Papering over obviously is not good, but has anyone a better idea to fix
> > > this? Or is "not fixing" for some reason an viable option here?
> > >
> >
> > I understand there is a regression, although kernel is not mainline
> > (hash df7443a96851 is unknown) and the only solutions were papering the
> > problem. Reverting commit is a temporary workaround. Moving nodes in DTS
> > is not acceptable because it hides actual problem and only solves this
> > one particular observed problem, while actual issue is still there. It
> > would be nice to be able to reproduce it on real mainline with normal
> > operating system (not AOSP) - with ramdiks/without/whatever. So far no
> > one did it, right?
>
> No, I did not try non-AOSP system yet. I'll try it tomorrow, if that
> helps. With mainline hash.

Hi, here is the crash report on db845c running vanilla v6.4-rc6 with a
debian build https://bugs.linaro.org/attachment.cgi?id=1142

And fwiw here is the db845c crash log with AOSP running vanilla
v6.4-rc6 https://bugs.linaro.org/attachment.cgi?id=1141

Regards,
Amit Pundir

PS: rootfs in this bug report doesn't matter much because I'm loading
all the kernel modules from a ramdisk and in the case of a crash the
UFS doesn't probe anyway.