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

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Message-ID: <CAMi1Hd28FJUjB8A-9YF7xpKOzSyNWXX3qung4aDjpLBhOvw_eA@mail.gmail.com>
Date:   Tue, 16 May 2023 23:41:58 +0530
From:   Amit Pundir <amit.pundir@...aro.org>
To:     Doug Anderson <dianders@...omium.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     Caleb Connolly <caleb.connolly@...aro.org>,
        Mark Brown <broonie@...nel.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 Mon, 15 May 2023 at 20:33, Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Mon, May 15, 2023 at 7:42 AM Amit Pundir <amit.pundir@...aro.org> wrote:
> >
> > On Sun, 14 May 2023 at 18:11, Caleb Connolly <caleb.connolly@...aro.org> wrote:
> > >
> > >
> > >
> > > On 13/05/2023 18:08, Amit Pundir wrote:
> > > > On Fri, 24 Mar 2023 at 19:05, Douglas Anderson <dianders@...omium.org> wrote:
> > > >>
> > > >> This reverts commit 58973046c1bf ("regulator: qcom-rpmh: Use
> > > >> PROBE_FORCE_SYNCHRONOUS"). Further digging into the problems that
> > > >> prompted the us to switch to synchronous probe showed that the root
> > > >> cause was a missing "rootwait" in the kernel command line
> > > >> arguments. Let's reinstate asynchronous probe.
> > > >
> > > > Hi, the asynchronous probe is broken on Dragonboard 845c (SDM845)
> > > > running AOSP (Android Open Source Project) with v6.4-rc1
> > > > https://bugs.linaro.org/show_bug.cgi?id=5975.
> > > > Can we please go back to synchronous probe.
> > > >
> > > > AOSP do not make use of rootwait, IIRC, but it is added by the
> > > > bootloader anyway. And the device fails to boot AOSP regardless of
> > > > "rootwait" bootarg being present or not.
> > >
> > > Could you try applying this diff to enable some log spam and let me know
> > > what you get? I'm keen to try and figure this one out. My mail client
> > > might crunch this a bit so I have pasted it here too
> > > https://p.calebs.dev/ab74b7@raw
> >
> > These prints add just enough delay for the UFS probe to succeed that I
> > can't reproduce the failure anymore.
>
> I'd prefer doing at least a little debugging before jumping to a
> revert. From looking at your dmesg [1], it looks as if the async probe
> is allowing RPMH to probe at the same time as "qcom-vadc-common".
> That's something that talks on the SPMI bus and is (potentially)
> talking to the same PMICs that RPMH-regulator is, right? I'm by no
> means an expert on how Qualcomm's PMICs work, but it seems plausible
> that the "qcom-vadc-common" is somehow causing problems and screwing
> up RPMH. Does that seem plausible to you?
>
> If so, one interesting way to track it down would be to move around
> delays. Put ~500ms sleep at the _end_ of vadc_probe(). Presumably that
> _won't_ fix the problem. Now put a ~500ms sleep at the beginning of
> vadc_probe(). Maybe that will fix the problem? If so, you can move the
> delay around to narrow down the conflict. My wild guess would be that
> vadc_reset() could be throwing things for a loop?
>
> If the above doesn't work, maybe we could add more tracing / printouts
> to see what is probing at the same time as RPMH?

Tried out a few changes today but none of them worked or were
effective enough to debug this crash further, other than setting
fw_devlink=permissive.

Adding more tracing / prints (BOOTTIME_TRACING and
FUNCTION_GRAPH_TRACER) didn't work and didn't help in reproducing the
crash either. They added just enough delay to boot the device
successfully everytime.

I tried to reason with the kernel modules which gets loaded before and
after the qcom-rpmh-regulator (QCOM_REBOOT_MODE, QCOM_PON, IIO/VADC,
SPMI_PMIC* etc) as suggested, but I run into the same crash even if I
disable those driver modules. So I don't think that the other driver
modules which gets loaded at around the same time as
qcom-rpmh-regulator by default have any impact on this failure.

The only way I can boot successfully everytime is if I boot with
fw_devlink=permissive bootarg. So I'll have to check if there is any
new dependency which got added recently in DT or somewhere else that
is causing this breakage.

Regards,
Amit Pundir

>
>
> [1] https://bugs.linaro.org/attachment.cgi?id=1135