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

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Message-ID: <CAMi1Hd2dO9WSfRQxZLhiyTjFrC_mX6ej9Q=u=Rd1XgRd5AU=jA@mail.gmail.com>
Date:   Mon, 19 Jun 2023 12:36:10 +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 Sat, 17 Jun 2023 at 12:51, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 16/06/2023 19:09, Amit Pundir wrote:
> > Hi,
> >
> > On Fri, 16 Jun 2023 at 13:57, Krzysztof Kozlowski
> > <krzysztof.kozlowski@...aro.org> wrote:
> >>
> >>
> >> So you have interconnect as module - this is not a supported setup. It
> >> might work with if all the modules are loaded very early or might not.
> >> Pinctrl is another driver which should be built-in.
> >>
> >> With your defconfig I see regular issue - console and system dies
> >> because of lack of interconnects, most likely. I don't see your WARNs -
> >> I just see usual hang.
> >>
> >> See:
> >> https://lore.kernel.org/all/20221021032702.1340963-1-krzysztof.kozlowski@linaro.org/
> >>
> >> If you want them to really be modules, then you need to fix all the
> >> dependencies (SOFTDEP?), probe ordering glitches. It's not a problem of
> >> DTS. Just because something can be built as module, does not mean it
> >> will work. We don't test it, we don't work with them as modules.
> >
> > I do somewhat agree with most of your arguments but not this one. If a
> > driver doesn't work as a module then it shouldn't be allowed to build
> > as a module.
>
> Of course you are right. That's why I am pushing against blindly adding
> "tristate" by everyone working on GKI. Because such folks like to make
> them tristate, but not actually test it or work on issues later.
>
> That's exactly the case from Google and Samsung patches here:
> https://lore.kernel.org/all/ac328b6a-a8e2-873d-4015-814cb4f5588e@canonical.com/
> and in previous submissions.
>
> > I took a quick look at the history of the interconnect
> > driver and it is tristate from the beginning. And not converted to a
> > modular build later-on like some of the other drivers to support GKI.
>
> OK, maybe it was never actually tested. Or maybe some versions were
> working on boards where debug serial does not have interconnect, but new
> chips just followed the pattern without testing?
> >
> >>
> >> It's kind of the same as here:
> >> https://lore.kernel.org/all/ac328b6a-a8e2-873d-4015-814cb4f5588e@canonical.com/
> >>
> >> I understand that we might have here regression, if these were working
> >> as modules, but I don't think we ever really committed to it. We can as
> >> well make it non-module to solve the regression.
> >
> > Sure. But since v6.4 is around the corner, can we merge this
> > workaround for now, while a proper fix is being worked upon.
>
> DTS workaround? No. I don't agree. Once it is merged it will not be fixed.
>
> I am perfectly fine though with making the interconnect or even rpmh
> regulator bool instead of tristate.

As Doug also mentioned in one of his earlier emails, this workaround
is only limited to one particular board. If I try to change the common
interconnect and/or rpmh driver then it will need ack from other stake
holders as well and I'll most likely get more pushback from that side.

Regards,
Amit Pundir