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

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Date:   Thu, 5 Oct 2023 14:22:49 +0530
From:   Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>
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 9/29/2023 12:08 AM, Manivannan Sadhasivam wrote:
> 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

Based up on the RPMH state the clock rates will be scaled accordingly.

- KC

>> 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
>>