linux-kernel - Re: [PATCH v6 6/6] PCI: qcom: Add OPP support to scale performance state of power domain

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Message-ID: <d7bb676c-f881-4be0-aff2-da50c9fa7eda@linaro.org>
Date: Fri, 12 Jan 2024 23:44:57 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Krishna chaitanya chundru <quic_krichai@...cinc.com>,
 Bjorn Andersson <andersson@...nel.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>
Cc: 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 6/6] PCI: qcom: Add OPP support to scale performance
 state of power domain

On 12.01.2024 15:22, Krishna chaitanya chundru wrote:
> QCOM Resource Power Manager-hardened (RPMh) is a hardware block which
> maintains hardware state of a regulator by performing max aggregation of
> the requests made by all of the processors.
> 
> PCIe controller can operate on different RPMh performance state of power
> domain based up on the speed of the link. And this performance state varies
> from target to target.
> 
> It is manadate to scale the performance state based up on the PCIe speed
> link operates so that SoC can run under optimum power conditions.
> 
> Add Operating Performance Points(OPP) support to vote for RPMh state based
> upon GEN speed link is operating.
> 
> OPP can handle ICC bw voting also, so move icc bw voting through opp
> framework if opp entries are present.
> 
> In PCIe certain gen speeds like GEN1x2 & GEN2X1 or GEN3x2 & GEN4x1 use
> same icc bw and has frequency, so use frequency based search to reduce
> number of entries in the opp table.
> 
> Don't initialize icc if opp is supported.
> 
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>
> ---

[...]

>  
> -static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
> +static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)

Or simply.. qcom_pcie_opp_update :) Especially with Dmitry's
suggestions

>  {
>  	struct dw_pcie *pci = pcie->pci;
> -	u32 offset, status;
> +	u32 offset, status, freq;
> +	struct dev_pm_opp *opp;
>  	int speed, width;
>  	int ret;
>  
> -	if (!pcie->icc_mem)
> -		return;
> -
>  	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>  	status = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA);
>  
> @@ -1424,11 +1424,42 @@ static void qcom_pcie_icc_update(struct qcom_pcie *pcie)
>  	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, status);
>  	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, status);
>  
> -	ret = icc_set_bw(pcie->icc_mem, 0, width * QCOM_PCIE_LINK_SPEED_TO_BW(speed));
> -	if (ret) {
> -		dev_err(pci->dev, "failed to set interconnect bandwidth: %d\n",
> -			ret);
> +	if (pcie->opp_supported) {
> +		switch (speed) {
> +		case 1:
> +			freq = 2500000;
> +			break;
> +		case 2:
> +			freq = 5000000;
> +			break;
> +		case 3:
> +			freq = 8000000;
> +			break;
> +		default:
> +			WARN_ON_ONCE(1);
> +			fallthrough;
> +		case 4:
> +			freq = 16000000;
> +			break;
> +		}
Might as well add gen5 and 6 rates of 3200.. and 6400.. since they're
hard-in-stone in the spec by now, AFAIK

Konrad