linux-kernel - [RFC PATCH 0/4] cpufreq: qcom-hw: Move clocks to CPU node

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Date:   Wed, 13 Jul 2022 12:22:55 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Johan Hovold <johan@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: [RFC PATCH 0/4] cpufreq: qcom-hw: Move clocks to CPU node

Hi,

A recent patch series, targeting enhancements in the OPP core, ended up breaking
cpufreq on some of the Qualcomm platforms [1]. Necessary adjustments are made in
the OPP core, a bit hacky though, to get it working for now but it would be
better to solve the problem at hand in a cleaner way. And this patchset is an
attempt towards the same.

cpufreq-hw is a hardware engine, which takes care of frequency
management for CPUs. The engine manages the clocks for CPU devices, but
it isn't the end consumer of the clocks, which are the CPUs in this
case.

For this reason, it looks incorrect to keep the clock related properties
in the cpufreq-hw node. They should really be present at the end user,
i.e. the CPUs.

The case was simple currently as all the devices, i.e. the CPUs, that
the engine manages share the same clock names. What if the clock names
are different for different CPUs or clusters ? How will keeping the
clock properties in the cpufreq-hw node work in that case ?

This design creates further problems for frameworks like OPP, which
expects all such details (clocks) to be present in the end device node
itself, instead of another related node.

This patchset moves the clock properties to the node that uses them instead,
i.e. the CPU nodes and makes necessary adjustments at other places.

After this is applied, I can drop the unnecessary change from the OPP core, but
I wanted to discuss if this is a step in the right direction or not first and so
the RFC.

--
Viresh

[1] https://lore.kernel.org/lkml/YsxSkswzsqgMOc0l@hovoldconsulting.com/

Viresh Kumar (4):
  dt-bindings: cpufreq-qcom-hw: Move clocks to CPU nodes
  arm64: dts: qcom: Move clocks to CPU nodes
  cpufreq: qcom-cpufreq-hw: Clocks are moved to CPU nodes
  cpufreq: qcom-cpufreq-hw: Register config_clks helper

 .../bindings/cpufreq/cpufreq-qcom-hw.yaml     | 31 ++++----
 arch/arm64/boot/dts/qcom/sc7180.dtsi          | 19 ++++-
 arch/arm64/boot/dts/qcom/sc7280.dtsi          | 18 ++++-
 arch/arm64/boot/dts/qcom/sdm845.dtsi          | 19 ++++-
 arch/arm64/boot/dts/qcom/sm6350.dtsi          | 18 ++++-
 arch/arm64/boot/dts/qcom/sm8150.dtsi          | 19 ++++-
 arch/arm64/boot/dts/qcom/sm8250.dtsi          | 18 ++++-
 arch/arm64/boot/dts/qcom/sm8350.dtsi          | 19 ++++-
 arch/arm64/boot/dts/qcom/sm8450.dtsi          | 18 ++++-
 drivers/cpufreq/qcom-cpufreq-hw.c             | 75 ++++++++++++++-----
 10 files changed, 199 insertions(+), 55 deletions(-)

-- 
2.31.1.272.g89b43f80a514