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

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Message-ID: <CAMi1Hd1Upo8zV4MPtdqHgEaMQ72yK0gZgf5Z4uOaqKqhw8Hndg@mail.gmail.com>
Date:   Wed, 7 Jun 2023 14:47:07 +0530
From:   Amit Pundir <amit.pundir@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Doug Anderson <dianders@...omium.org>,
        Mark Brown <broonie@...nel.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>,
        regressions <regressions@...ts.linux.dev>,
        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 Wed, 7 Jun 2023 at 13:19, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 07/06/2023 01:34, Doug Anderson wrote:
> > Hi,
> >
> > On Fri, Jun 2, 2023 at 9:12 AM Amit Pundir <amit.pundir@...aro.org> 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.
> >>
> >> Link: https://lore.kernel.org/all/CAMi1Hd1avQDcDQf137m2auz2znov4XL8YGrLZsw5edb-NtRJRw@mail.gmail.com/
> >> Signed-off-by: Amit Pundir <amit.pundir@...aro.org>
> >> ---
> >>  arch/arm64/boot/dts/qcom/sdm845-db845c.dts | 24 +++++++++++-----------
> >>  1 file changed, 12 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> >> index e14fe9bbb386..df2fde9063dc 100644
> >> --- a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> >> +++ b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
> >> @@ -301,6 +301,18 @@ regulators-0 {
> >>                 vdd-l26-supply = <&vreg_s3a_1p35>;
> >>                 vin-lvs-1-2-supply = <&vreg_s4a_1p8>;
> >>
> >> +               vreg_lvs1a_1p8: lvs1 {
> >> +                       regulator-min-microvolt = <1800000>;
> >> +                       regulator-max-microvolt = <1800000>;
> >> +                       regulator-always-on;
> >> +               };
> >> +
> >> +               vreg_lvs2a_1p8: lvs2 {
> >> +                       regulator-min-microvolt = <1800000>;
> >> +                       regulator-max-microvolt = <1800000>;
> >> +                       regulator-always-on;
> >> +               };
> >> +
> >>                 vreg_s3a_1p35: smps3 {
> >>                         regulator-min-microvolt = <1352000>;
> >>                         regulator-max-microvolt = <1352000>;
> >> @@ -381,18 +393,6 @@ vreg_l26a_1p2: ldo26 {
> >>                         regulator-max-microvolt = <1200000>;
> >>                         regulator-initial-mode = <RPMH_REGULATOR_MODE_HPM>;
> >>                 };
> >> -
> >> -               vreg_lvs1a_1p8: lvs1 {
> >> -                       regulator-min-microvolt = <1800000>;
> >> -                       regulator-max-microvolt = <1800000>;
> >> -                       regulator-always-on;
> >> -               };
> >> -
> >> -               vreg_lvs2a_1p8: lvs2 {
> >> -                       regulator-min-microvolt = <1800000>;
> >> -                       regulator-max-microvolt = <1800000>;
> >> -                       regulator-always-on;
> >> -               };
> >
> > This is a hack, but it at least feels less bad than reverting the
> > async probe patch. I'll leave it to Bjorn to decide if he's OK with
> > it. Personally, it feels like this would deserve a comment in the dts
> > to document that these regulators need to be listed first.
> >
> > Ideally, we could still work towards a root cause. I added a few more
> > ideas to help with root causing in reply to the original thread about
> > this.
> >
> > https://lore.kernel.org/r/CAD=FV=UKyjRNZG-ED2meUAR9aXdco+AbUTHiKixTzjCkaJbjTg@mail.gmail.com/
>
> We do not shape DTS based on given OS behavior. AOSP needs this, BSD
> needs that and Linux needs something else. Next time someone will move
> these regulators down because on his system probing is from end of list,
> not beginning and he has the same problem.
>
> No, really, are we going to reshuffle nodes because AOSP needs it?

Hi, other than the fact that I reproduced it on AOSP, there is nothing
AOSP specific in this patch. I'm sure there may be another
platforms/OS (which load kernel modules from a ramdisk) that may trip
on this bug. But I can try reproducing it on an OS of your choice if
it helps.

Regards,
Amit Pundir

>
> Best regards,
> Krzysztof
>