linux-kernel - Re: [PATCH v6 5/6] arm64: dts: qcom: sm8450: Add opp table support to PCIe

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Date: Mon, 29 Jan 2024 21:34:20 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Johan Hovold <johan+linaro@...nel.org>,
	Brian Masney <bmasney@...hat.com>,
	Georgi Djakov <djakov@...nel.org>, linux-arm-msm@...r.kernel.org,
	vireshk@...nel.org, quic_vbadigan@...cinc.com,
	quic_skananth@...cinc.com, quic_nitegupt@...cinc.com,
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 5/6] arm64: dts: qcom: sm8450: Add opp table support
 to PCIe

On Fri, Jan 12, 2024 at 07:52:04PM +0530, Krishna chaitanya chundru wrote:
> PCIe needs to choose the appropriate performance state of RPMH power
> domain and interconnect bandwidth based up on the PCIe gen speed.
> 
> Add the OPP table support to specify RPMH performance states and
> interconnect peak bandwidth.
> 
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---
>  arch/arm64/boot/dts/qcom/sm8450.dtsi | 74 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 74 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> index 6b1d2e0d9d14..eab85ecaeff0 100644
> --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> @@ -1827,7 +1827,32 @@ pcie0: pcie@...0000 {
>  			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-2500000 {
> +					opp-hz = /bits/ 64 <2500000>;
> +					required-opps = <&rpmhpd_opp_low_svs>;
> +					opp-peak-kBps = <250000 250000>;

This is a question for Viresh: We already have macros in the driver to derive
the bandwidth based on link speed. So if OPP core exposes a callback to allow
the consumers to set the bw on its own, we can get rid of this entry.

Similar to config_clks()/config_regulators(). Is that feasible?

- Mani

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