linux-kernel - Re: [PATCH 2/3] arm64: dts: qcom: sdm845-mtp: Add RPMh VRM/XOB regulators

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Date:   Tue, 10 Jul 2018 15:55:40 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     David Collins <collinsd@...eaurora.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Manu Gautam <mgautam@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        devicetree@...r.kernel.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        David Brown <david.brown@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-soc@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/3] arm64: dts: qcom: sdm845-mtp: Add RPMh VRM/XOB regulators

Hi

On Tue, Jul 10, 2018 at 3:32 PM, David Collins <collinsd@...eaurora.org> wrote:
> Hello Doug,
>
> On 07/10/2018 03:02 PM, Douglas Anderson wrote:
> ...
>> +             vdd-s1-supply = <&vph_pwr>;
>> +             vdd-s2-supply = <&vph_pwr>;
>> +             vdd-s3-supply = <&vph_pwr>;
>> +             vdd-s4-supply = <&vph_pwr>;
>> +             vdd-s5-supply = <&vph_pwr>;
>> +             vdd-s6-supply = <&vph_pwr>;
>> +             vdd-s7-supply = <&vph_pwr>;
>> +             vdd-s8-supply = <&vph_pwr>;
>> +             vdd-s9-supply = <&vph_pwr>;
>> +             vdd-s10-supply = <&vph_pwr>;
>> +             vdd-s11-supply = <&vph_pwr>;
>> +             vdd-s12-supply = <&vph_pwr>;
>> +             vdd-s13-supply = <&vph_pwr>;
>> +             vdd-l1-l27-supply = <&vreg_s7a_1p025>;
>> +             vdd-l2-l8-l17-supply = <&vreg_s3a_1p35>;
>> +             vdd-l3-l11-supply = <&vreg_s7a_1p025>;
>> +             vdd-l4-l5-supply = <&vreg_s7a_1p025>;
>> +             vdd-l6-supply = <&vph_pwr>;
>> +             vdd-l7-l12-l14-l15-supply = <&vreg_s5a_2p04>;
>> +             vdd-l9-supply = <&vreg_bob>;
>> +             vdd-l10-l23-l25-supply = <&vreg_bob>;
>> +             vdd-l13-l19-l21-supply = <&vreg_bob>;
>> +             vdd-l16-l28-supply = <&vreg_bob>;
>> +             vdd-l18-l22-supply = <&vreg_bob>;
>> +             vdd-l20-l24-supply = <&vreg_bob>;
>> +             vdd-l26-supply = <&vreg_s3a_1p35>;
>> +             vin-lvs-1-2-supply = <&vreg_s4a_1p8>;
>
> I would suggest not specifying any of these regulator parent supplies in
> device tree.  RPMh will be enforcing all regulator parent-child
> dependencies.  Therefore, handling the dependencies in Linux is redundant.
>  It will result in additional RPMh requests as well as more time spent in
> regulator framework calls.  Overall, it will lead to slightly lower
> performance.  Note that while specifying the parent supplies results in
> less efficient runtime behavior, it is not technically wrong so you could
> keep them in place if you prefer.

Interesting.  ...so RPMh will automatically turn on parent regulators
when their children are enabled (assuming that the parent regulator is
also RPMh controlled)?

Personally I'd still prefer to see Linux managing its own state and
relying less on RPMh-automatic stuff, but I'd defer to Bjorn / Andy
(or others) to override me.

-Doug