linux-kernel - Re: [PATCH 0/3] opp: Add bw_factor support to adjust bandwidth dynamically

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Message-ID: <0dfe9025-de00-4ec2-b6ca-5ef8d9414301@oss.qualcomm.com>
Date: Fri, 1 Aug 2025 12:05:43 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: 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 0/3] opp: Add bw_factor support to adjust bandwidth
 dynamically

Hi Viresh,

Can you please review this once.

Thanks & Regards,
Krishna Chaitanya.

On 7/17/2025 7:31 PM, Krishna Chaitanya Chundru wrote:
> The existing OPP table in the device tree for PCIe is shared across
> different link configurations such as data rates 8GT/s x2 and 16GT/s x1.
> These configurations often operate at the same frequency, allowing them
> to reuse the same OPP entries. However, 8GT/s and 16 GT/s may have
> different characteristics beyond frequency—such as RPMh votes in QCOM
> case, which cannot be represented accurately when sharing a single OPP.
> 
> To avoid conflicts and duplication in the device tree, we now define only
> one set of OPP entries per table and introduce a new mechanism to adjust
> bandwidth dynamically using a `bw_factor`.
> 
> The `bw_factor` is a multiplier applied to the average and peak bandwidth
> values of an OPP entry. This allows PCIe drivers to modify the effective
> bandwidth at runtime based on the actual link width without needing
> separate OPP entries for each configuration.
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
> Krishna Chaitanya Chundru (3):
>        opp: Add bw_factor support to adjust bandwidth dynamically
>        PCI: qcom: Use bw_factor to adjust bandwidth based on link width
>        arm64: dts: qcom: sm8450: Keep only x1 lane PCIe OPP entries
> 
>   arch/arm64/boot/dts/qcom/sm8450.dtsi   | 17 ++--------------
>   drivers/opp/core.c                     | 37 ++++++++++++++++++++++++++++++++--
>   drivers/opp/opp.h                      |  2 ++
>   drivers/pci/controller/dwc/pcie-qcom.c |  8 ++++++--
>   include/linux/pm_opp.h                 |  7 +++++++
>   5 files changed, 52 insertions(+), 19 deletions(-)
> ---
> base-commit: e2291551827fe5d2d3758c435c191d32b6d1350e
> change-id: 20250717-opp_pcie-793160b2b113
> 
> Best regards,