linux-kernel - Re: [PATCH v4 7/7] PCI: qcom: Use frequency and level based OPP lookup

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Message-ID: <6b9fb458-bce1-4d16-a708-b05fdeb22d4d@linaro.org>
Date: Wed, 20 Aug 2025 10:55:01 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
 Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
 Stephen Boyd <sboyd@...nel.org>, "Rafael J. Wysocki" <rafael@...nel.org>,
 Manivannan Sadhasivam <mani@...nel.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczyński <kwilczynski@...nel.org>,
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v4 7/7] PCI: qcom: Use frequency and level based OPP
 lookup

On 20/08/2025 10:28, Krishna Chaitanya Chundru wrote:
> PCIe supports multiple data rates that may operate at the same clock
> frequency by varying the link width. In such cases, frequency alone
> is insufficient to identify the correct OPP. Use the newly introduced
> dev_pm_opp_find_key_exact() API to match both frequency and
> level when selecting an OPP, here level indicates PCIe data rate.
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
>   drivers/pci/controller/dwc/pcie-qcom.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 294babe1816e4d0c2b2343fe22d89af72afcd6cd..4f40fc7b828483419b87057c53e2f754811bdda0 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1555,6 +1555,7 @@ static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
>   {
>   	u32 offset, status, width, speed;
>   	struct dw_pcie *pci = pcie->pci;
> +	struct dev_pm_opp_key key;
>   	unsigned long freq_kbps;
>   	struct dev_pm_opp *opp;
>   	int ret, freq_mbps;
> @@ -1582,8 +1583,10 @@ static void qcom_pcie_icc_opp_update(struct qcom_pcie *pcie)
>   			return;
>   
>   		freq_kbps = freq_mbps * KILO;
> -		opp = dev_pm_opp_find_freq_exact(pci->dev, freq_kbps * width,
> -						 true);
> +		key.freq = freq_kbps * width;
> +		key.level = speed;
> +		key.bw = 0;
> +		opp = dev_pm_opp_find_key_exact(pci->dev, key, true);
>   		if (!IS_ERR(opp)) {
>   			ret = dev_pm_opp_set_opp(pci->dev, opp);
>   			if (ret)
> 

Fine but you should still support DTs without the opp-level property as fallback,
since stable kernels has the opp tables without level property (v6.12+ for 8450/x1e, v6.16 for 8550/8650)

Neil