linux-kernel - Re: [PATCH v1 07/10] arm64: dts: qcom: ipq5332: populate the opp table based on the eFuse

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Date:   Thu, 5 Oct 2023 14:39:43 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Varadarajan Narayanan <quic_varada@...cinc.com>
Cc:     ilia.lin@...nel.org, agross@...nel.org, andersson@...nel.org,
        konrad.dybcio@...aro.org, rafael@...nel.org,
        viresh.kumar@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        mturquette@...libre.com, sboyd@...nel.org,
        quic_kathirav@...cinc.com, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v1 07/10] arm64: dts: qcom: ipq5332: populate the opp
 table based on the eFuse

On Thu, 5 Oct 2023 at 12:58, Varadarajan Narayanan
<quic_varada@...cinc.com> wrote:
>
> On Thu, Sep 07, 2023 at 04:59:28PM +0300, Dmitry Baryshkov wrote:
> > On Thu, 7 Sept 2023 at 08:23, Varadarajan Narayanan
> > <quic_varada@...cinc.com> wrote:
> > >
> > > IPQ53xx have different OPPs available for the CPU based on
> > > SoC variant. This can be determined through use of an eFuse
> > > register present in the silicon.
> > >
> > > Add support to read the eFuse and populate the OPPs based on it.
> > >
> > > Signed-off-by: Kathiravan T <quic_kathirav@...cinc.com>
> > > Signed-off-by: Varadarajan Narayanan <quic_varada@...cinc.com>
> > > ---
> > >  arch/arm64/boot/dts/qcom/ipq5332.dtsi | 34 +++++++++++++++++++++++++++++++---
> > >  1 file changed, 31 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/arch/arm64/boot/dts/qcom/ipq5332.dtsi b/arch/arm64/boot/dts/qcom/ipq5332.dtsi
> > > index 82761ae..3ca3f34 100644
> > > --- a/arch/arm64/boot/dts/qcom/ipq5332.dtsi
> > > +++ b/arch/arm64/boot/dts/qcom/ipq5332.dtsi
> > > @@ -91,11 +91,34 @@
> > >         };
> > >
> > >         cpu_opp_table: opp-table-cpu {
> > > -               compatible = "operating-points-v2";
> > > +               compatible = "operating-points-v2-kryo-cpu";
> > >                 opp-shared;
> > > +               nvmem-cells = <&cpu_speed_bin>;
> > > +               nvmem-cell-names = "speed_bin";
> > > +
> > > +               /*
> > > +                * Listed all supported CPU frequencies and opp-supported-hw
> > > +                * values to select CPU frequencies based on the limits fused.
> > > +                * ------------------------------------------------------------
> > > +                * Frequency     BIT3   BIT2   BIT1    BIT0    opp-supported-hw
> > > +                *              1.0GHz 1.2GHz 1.5GHz No Limit
> > > +                * ------------------------------------------------------------
> > > +                * 1100000000     1      1      1       1            0xF
> > > +                * 1500000000     0      0      1       1            0x3
> > > +                * -----------------------------------------------------------
> > > +                */
> >
> > This can probably go to the commit message instead.
>
> Ok
>
> > > +
> > > +               opp-1100000000 {
> > > +                       opp-hz = /bits/ 64 <1100000000>;
> >
> > But your table shows 1.0 GHz and 1.2 GHz instead of 1.1 GHz
>
> Will update it.
>
> > > +                       opp-microvolt = <850000>;
> > > +                       opp-supported-hw = <0xF>;
> > > +                       clock-latency-ns = <200000>;
> > > +               };
> > >
> > > -               opp-1488000000 {
> > > -                       opp-hz = /bits/ 64 <1488000000>;
> > > +               opp-1500000000 {
> > > +                       opp-hz = /bits/ 64 <1500000000>;
> >
> > So, 1.488 GHz or 1.5 GHz?
>
> 1.5 GHz
>
> > > +                       opp-microvolt = <950000>;
> >
> > Which regulator is controlled by this microvolt?
>
> Based on the SKU, the XBL sets up the regulator to provide 950000uV
> on CPUs capable of running 1.5G and 850000uV on other SKUs. Linux
> doesn't control it.

Then why do you need this property here in the first place?


-- 
With best wishes
Dmitry