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From:   Amit Pundir <amit.pundir@linaro.org>
Date:   Wed, 2 Sep 2020 18:57:48 +0530
Message-ID: <CAMi1Hd2ZakhXm+qNh-VMF_OndqCaQxxY3CC+UfQ6x2PyL_5sPQ@mail.gmail.com>
Subject: Re: [PATCH v6] arm64: dts: qcom: Add support for Xiaomi Poco F1 (Beryllium)
To:     Konrad Dybcio <konradybcio@gmail.com>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        John Stultz <john.stultz@linaro.org>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        dt <devicetree@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>
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On Mon, 31 Aug 2020 at 13:28, Konrad Dybcio <konradybcio@gmail.com> wrote:
>
> > Hi Konrad,
> >
> > I couldn't find answer to your question around missing
> > (regulatorname)-supply properties. Need help in figuring out that
> > part.
>
> When the phone boots up and RPM(H) kicks in, you should see regulators
> probing like "s1 supplied by foo". Without the *-supply stuff, you
> will likely get "supplied by regulator-dummy". This happens here [1]
> and to my knowledge it is the "eletrical wiring" for Linux, as in it
> makes Linux aware of which regulators are connected electrically to
> the same supply (so that kernel knows when the supply is on and what
> voltage it's at). For qcom platforms, this is common per-pmic (afaik,
> please check if you are able to!), so you can likely just copy-paste
> that part from msm8998-mtp.dtsi, which also uses pm(i)8998.

Thank you for the pointer. I dug around the vph_pwr fixed-regulator
node used by fellow sdm845 devices. I assume it is safe to copy it
from sdm845-mtp but I couldn't verify it in the downstream
device-tree, so I'm a bit hesitant. My main concern is that I don't
want to burn down my only device :)

I did find a few regulator nodes downstream which matches with
upstream sdm845-mtp but since I'm not using any of them in my
beryllium dts, I'm going to skip them for now.

As you pointed out, in case of regulator lookup failure Linux will
fall back to dummy regulators, which is working fine for me so far.
Also I see that vdd-*-supply properties are optional according to
Documentation/devicetree/bindings/regulator/qcom,rpmh-regulator.txt,
so I assume it is safe to skip them?

Regards,
Amit Pundir

>
> Konrad