linux-kernel - Re: [PATCH v5 5/5] PCI: qcom: Use frequency and level based OPP lookup

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Message-ID: <f0f1219b-672e-4793-8501-ea31e7cc9575@oss.qualcomm.com>
Date: Wed, 22 Oct 2025 18:37:41 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
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 v5 5/5] PCI: qcom: Use frequency and level based OPP
 lookup

On 10/13/25 12:53 PM, Krishna Chaitanya Chundru wrote:
> PCIe link configurations such as 8GT/s x2 and 16GT/s x1 may operate at
> the same frequency but differ in other characteristics like RPMh votes.
> The existing OPP selection based solely on frequency cannot distinguish
> between such cases.
> 
> 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.
> 
> To support older device tree's where opp-level is not defined, check if
> opp-level is present or not using dev_pm_opp_find_level_exact(). if
> not present fallback to frequency only match.
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 805edbbfe7eba496bc99ca82051dee43d240f359..03b3a1d3a40359a0c70704873b72539ffa43e722 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1565,6 +1565,7 @@ 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;

You need to zero-initialize this, or it'll explode the second
struct dev_pm_opp_key {} grows

Konrad