linux-kernel - Re: [PATCH v1 2/3] arm64: dts: qcom: sm8450: Add opp table support to PCIe

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Message-ID: <dc14acb4-9fe8-4b3b-a9da-7f7915de4d5c@quicinc.com>
Date:   Wed, 16 Aug 2023 12:35:54 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
CC:     <manivannan.sadhasivam@...aro.org>, <helgaas@...nel.org>,
        <linux-pci@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_vbadigan@...cinc.com>,
        <quic_nitegupt@...cinc.com>, <quic_skananth@...cinc.com>,
        <quic_ramkri@...cinc.com>, <quic_parass@...cinc.com>,
        <krzysztof.kozlowski@...aro.org>, Andy Gross <agross@...nel.org>,
        "Bjorn Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v1 2/3] arm64: dts: qcom: sm8450: Add opp table support
 to PCIe

On Tue, Aug 15, 2023 at 05:56:47PM +0530, Krishna chaitanya chundru wrote:
> PCIe needs to choose the appropriate performance state of RPMH power
> domain based upon the PCIe gen speed.
> 
> So, let's add the OPP table support to specify RPMH performance states.
> 
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  arch/arm64/boot/dts/qcom/sm8450.dtsi | 47 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> index 595533a..681ea9c 100644
> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> @@ -381,6 +381,49 @@
>  		};
>  	};
>  
> +	pcie0_opp_table: opp-table-pcie0 {
> +		compatible = "operating-points-v2";
> +
> +		opp-2500000 {
> +			opp-hz = /bits/ 64 <2500000>;
> +			opp-level = <RPMH_REGULATOR_LEVEL_LOW_SVS>;
> +		};
> +
> +		opp-5000000 {
> +			opp-hz = /bits/ 64 <5000000>;
> +			opp-level = <RPMH_REGULATOR_LEVEL_LOW_SVS>;
> +		};
> +
> +		opp-8000000 {
> +			opp-hz = /bits/ 64 <8000000>;
> +			opp-level = <RPMH_REGULATOR_LEVEL_LOW_SVS>;
> +		};
> +	};
> +
> +	pcie1_opp_table: opp-table-pcie1 {
> +		compatible = "operating-points-v2";
> +
> +		opp-2500000 {
> +			opp-hz = /bits/ 64 <2500000>;
> +			opp-level = <RPMH_REGULATOR_LEVEL_LOW_SVS>;
> +		};
> +
> +		opp-5000000 {
> +			opp-hz = /bits/ 64 <5000000>;
> +			opp-level = <RPMH_REGULATOR_LEVEL_LOW_SVS>;
> +		};
> +
> +		opp-8000000 {
> +			opp-hz = /bits/ 64 <8000000>;
> +			opp-level = <RPMH_REGULATOR_LEVEL_LOW_SVS>;
> +		};
> +
> +		opp-16000000 {
> +			opp-hz = /bits/ 64 <16000000>;
> +			opp-level = <RPMH_REGULATOR_LEVEL_NOM>;
> +		};
> +	};
> +

Should not we using required-opps property to pass the
rpmhpd_opp_xxx phandle so that when this OPP is selected based on your
clock rate, the appropriate OPP (voltage) would be selected on the RPMH side?

Please see SDHCI/MMC voting (sdhc2_opp_table) as an example.

Thanks,
Pavan