linux-kernel - Re: [PATCH v10 4/6] arm64: dts: qcom: sm8450: Add OPP table support to PCIe

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Date: Mon, 22 Apr 2024 20:14:31 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, johan+linaro@...nel.org,
	bmasney@...hat.com, djakov@...nel.org,
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	vireshk@...nel.org, quic_vbadigan@...cinc.com,
	quic_skananth@...cinc.com, quic_nitegupt@...cinc.com,
	quic_parass@...cinc.com, krzysztof.kozlowski@...aro.org
Subject: Re: [PATCH v10 4/6] arm64: dts: qcom: sm8450: Add OPP table support
 to PCIe

On Tue, Apr 09, 2024 at 03:43:22PM +0530, Krishna chaitanya chundru wrote:
> PCIe needs to choose the appropriate performance state of RPMh power

'PCIe host controller driver'

> domain and interconnect bandwidth based up on the PCIe data rate.

'based on the PCIe data rate'

> 
> Add the OPP table support to specify RPMh performance states and

'Hence, add...'

> interconnect peak bandwidth.
> 
> Different link configurations may share the same aggregate bandwidth,

'It should be noted that the different...'

> e.g., a 2.5 GT/s x2 link and a 5.0 GT/s x1 link have the same bandwidth
> and share the same OPP entry.
> 
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  arch/arm64/boot/dts/qcom/sm8450.dtsi | 77 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 77 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> index 615296e13c43..9dfe16012726 100644
> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> @@ -1855,7 +1855,35 @@ &mc_virt SLAVE_EBI1 QCOM_ICC_TAG_ALWAYS>,
>  			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";
> +
> +				/* GEN 1 x1 */
> +				opp-2500000 {
> +					opp-hz = /bits/ 64 <2500000>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +					opp-peak-kBps = <250000 1>;
> +				};
> +
> +				/* GEN 2 x1 */
> +				opp-5000000 {
> +					opp-hz = /bits/ 64 <5000000>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +					opp-peak-kBps = <500000 1>;
> +				};
> +
> +				/* GEN 3 x1 */
> +				opp-8000000 {
> +					opp-hz = /bits/ 64 <8000000>;

I doubt this value. See below...

> +					required-opps = <&rpmhpd_opp_nom>;
> +					opp-peak-kBps = <984500 1>;
> +				};
> +			};
> +
>  		};
>  
>  		pcie0_phy: phy@...6000 {
> @@ -1982,7 +2010,56 @@ &mc_virt SLAVE_EBI1 QCOM_ICC_TAG_ALWAYS>,
>  			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";
> +
> +				/* GEN 1 x1 */
> +				opp-2500000 {
> +					opp-hz = /bits/ 64 <2500000>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +					opp-peak-kBps = <250000 1>;
> +				};
> +
> +				/* GEN 1 x2 GEN 2 x1 */
> +				opp-5000000 {
> +					opp-hz = /bits/ 64 <5000000>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +					opp-peak-kBps = <500000 1>;
> +				};
> +
> +				/* GEN 2 x2 */
> +				opp-10000000 {
> +					opp-hz = /bits/ 64 <10000000>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +					opp-peak-kBps = <1000000 1>;
> +				};
> +
> +				/* GEN 3 x1 */
> +				opp-8000000 {
> +					opp-hz = /bits/ 64 <8000000>;

GEN 3 x1 frequency is lower than GEN 2 x2? This looks strange. Both should be of
same frequency.

> +					required-opps = <&rpmhpd_opp_nom>;
> +					opp-peak-kBps = <984500 1>;
> +				};
> +
> +				/* GEN 3 x2 GEN 4 x1 */

'GEN 3 x2 and GEN 4 x1'

- Mani

-- 
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