linux-kernel - Re: [PATCH v5 2/5] arm64: dts: qcom: sm8450: Add opp table support to PCIe

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Date:   Thu, 28 Sep 2023 20:38:08 +0200
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc:     agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        vireshk@...nel.org, nm@...com, sboyd@...nel.org,
        lpieralisi@...nel.org, kw@...ux.com, robh@...nel.org,
        bhelgaas@...gle.com, rafael@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, quic_vbadigan@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_ramkri@...cinc.com, quic_parass@...cinc.com
Subject: Re: [PATCH v5 2/5] arm64: dts: qcom: sm8450: Add opp table support
 to PCIe

On Thu, Sep 07, 2023 at 11:30:30AM +0530, Krishna chaitanya chundru wrote:
> PCIe needs to choose the appropriate performance state of RPMH power
> domain based up on the PCIe gen speed.
> 
> So let's add the OPP table support to specify RPMH performance states.
> 
> Use opp-level for the PCIe gen speed for easier use.
> 

So, you just want to control RPMh performance state using OPP and not clock
rates? What will happen if you switch to lowest performance state of RPMh but
still run PCIe clocks at max rate?

- Mani

> 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 2a60cf8..a6264a5 100644
> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> @@ -1820,7 +1820,28 @@
>  			pinctrl-names = "default";
>  			pinctrl-0 = <&pcie0_default_state>;
>  
> +			operating-points-v2 = <&pcie0_opp_table>;
> +
>  			status = "disabled";
> +
> +			pcie0_opp_table: opp-table {
> +				compatible = "operating-points-v2";
> +
> +				opp-1 {
> +					opp-level = <1>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +				};
> +
> +				opp-2 {
> +					opp-level = <2>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +				};
> +
> +				opp-3 {
> +					opp-level = <3>;
> +					required-opps = <&rpmhpd_opp_nom>;
> +				};
> +			};
>  		};
>  
>  		pcie0_phy: phy@...6000 {
> @@ -1932,7 +1953,33 @@
>  			pinctrl-names = "default";
>  			pinctrl-0 = <&pcie1_default_state>;
>  
> +			operating-points-v2 = <&pcie1_opp_table>;
> +
>  			status = "disabled";
> +
> +			pcie1_opp_table: opp-table {
> +				compatible = "operating-points-v2";
> +
> +				opp-1 {
> +					opp-level = <1>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +				};
> +
> +				opp-2 {
> +					opp-level = <2>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +				};
> +
> +				opp-3 {
> +					opp-level = <3>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +				};
> +
> +				opp-4 {
> +					opp-level = <4>;
> +					required-opps = <&rpmhpd_opp_nom>;
> +				};
> +			};
>  		};
>  
>  		pcie1_phy: phy@...f000 {
> -- 
> 2.7.4
> 

-- 
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