linux-kernel - Re: [PATCH 3/3] arm64: dts: qcom: ipq5018: enable the CPUFreq support

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Message-ID: <1aad08e5-d3a4-e3cf-3535-deb54ecf0169@quicinc.com>
Date:   Thu, 31 Aug 2023 11:40:41 +0530
From:   Gokul Sriram P <quic_gokulsri@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC:     Robert Marko <robimarko@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <mturquette@...libre.com>,
        <sboyd@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <jassisinghbrar@...il.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_varada@...cinc.com>, <quic_srichara@...cinc.com>
Subject: Re: [PATCH 3/3] arm64: dts: qcom: ipq5018: enable the CPUFreq support


On 8/31/2023 1:12 AM, Dmitry Baryshkov wrote:
> On Wed, 30 Aug 2023 at 21:32, Gokul Sriram P <quic_gokulsri@...cinc.com> wrote:
>>
>>>>>>>     #include <dt-bindings/interrupt-controller/arm-gic.h>
>>>>>>>     #include <dt-bindings/clock/qcom,gcc-ipq5018.h>
>>>>>>>     #include <dt-bindings/reset/qcom,gcc-ipq5018.h>
>>>>>>> +#include <dt-bindings/clock/qcom,apss-ipq.h>
>>>>>> c is before r.
>>    Sure, will update.
>>
>> [...]
>>>>>>> +   cpu_opp_table: opp-table-cpu {
>>>>>>> +           compatible = "operating-points-v2";
>>>>>>> +           opp-shared;
>>>>>>> +
>>>>>>> +           opp-1008000000 {
>>>>>>> +                   opp-hz = /bits/ 64 <1008000000>;
>>>>>>> +                   opp-microvolt = <1100000>;
>>>>>>> +                   clock-latency-ns = <200000>;
>>>>>> And the rest of OPPs?
>>>>> Hi Krzysztof,
>>>>> IPQ5018 only supports running at 1.1GHz, but its running at 800MHz
>>>>> by default from the bootloader so there is only one OPP.
>>>> Isn't this contradictory? If it is running at 800 initially, then it
>>>> supports running at 800...
>>> I can only guess that it's not validated at 800MHz.
>> As per the h/w design team, there is negligible power or thermal benefit
>> by lowering to 800MHz clock.
>> Hence, 800MHz opp wasn't included here.
> Just my 2c. If 800 MHz is supported, it should be included. Even if
> just to prevent the kernel from throwing a warning about the CPU
> running at the unsupported frequency. Then one can use scheduler
> tunings to prevent the CPU from going to 800 MHz state.

sure, understood. Will add opp at 800MHz. Thanks.

Regards,
Gokul