linux-kernel - [PATCH v3 0/3] OPP: Add support to find OPP for a set of keys

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Message-Id: <20250819-opp_pcie-v3-0-f8bd7e05ce41@oss.qualcomm.com>
Date: Tue, 19 Aug 2025 11:04:41 +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,
        Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Subject: [PATCH v3 0/3] OPP: Add support to find OPP for a set of keys

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.

In such cases, frequency alone is not sufficient to uniquely identify
an OPP. To support these scenarios, introduce a new API
dev_pm_opp_find_key_exact() that allows OPP lookup for set of keys like
frequency, level & bandwidth.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
---
Changes in v3:
- Always check for frequency match unless user doesn't pass it (Viresh).
- Make dev_pm_opp_key public and let user pass the key (Viresh).
- Include bandwidth as part of dev_pm_opp_key (Viresh).
- Link to v2: https://lore.kernel.org/r/20250818-opp_pcie-v2-0-071524d98967@oss.qualcomm.com

Changes in v2:
- Use opp-level to indentify data rate and use both frequency and level
  to identify the OPP. (Viresh)
- Link to v1: https://lore.kernel.org/r/20250717-opp_pcie-v1-0-dde6f452571b@oss.qualcomm.com

---
Krishna Chaitanya Chundru (3):
      OPP: Add support to find OPP for a set of keys
      arm64: dts: qcom: sm8450: Add opp-level to indicate PCIe data rates
      PCI: qcom: Use frequency and level based OPP lookup

 arch/arm64/boot/dts/qcom/sm8450.dtsi   |  41 +++++++++++---
 drivers/opp/core.c                     | 100 +++++++++++++++++++++++++++++++++
 drivers/pci/controller/dwc/pcie-qcom.c |   6 +-
 include/linux/pm_opp.h                 |  23 ++++++++
 4 files changed, 160 insertions(+), 10 deletions(-)
---
base-commit: c17b750b3ad9f45f2b6f7e6f7f4679844244f0b9
change-id: 20250717-opp_pcie-793160b2b113

Best regards,
-- 
Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>