linux-kernel - [PATCH v7 0/5] Add support for QCOM Core Power Reduction

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Date:   Fri, 29 Nov 2019 22:39:10 +0100
From:   Niklas Cassel <niklas.cassel@...aro.org>
To:     linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org
Cc:     amit.kucheria@...aro.org, sboyd@...nel.org, vireshk@...nel.org,
        bjorn.andersson@...aro.org, ulf.hansson@...aro.org,
        Niklas Cassel <niklas.cassel@...aro.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v7 0/5] Add support for QCOM Core Power Reduction

This series adds support for Core Power Reduction (CPR), a form of
Adaptive Voltage Scaling (AVS), found on certain Qualcomm SoCs.

This series is based on top of the qcs404 cpufreq patch series that
hasn't landed yet:
https://patchwork.kernel.org/project/linux-arm-msm/list/?series=207821
as well as that series' matching device tree changes:
https://patchwork.kernel.org/project/linux-arm-msm/list/?series=207831

For testing purposes, this patch series, including the dependencies
listed above, is available on the following git tag:
https://git.linaro.org/people/niklas.cassel/kernel.git/log/?h=cpr-v7

CPR is a technology that reduces core power on a CPU or on other device.
It reads voltage settings from efuses (that have been written in
production), it uses these voltage settings as initial values, for each
OPP.

After moving to a certain OPP, CPR monitors dynamic factors such as
temperature, etc. and adjusts the voltage for that frequency accordingly
to save power and meet silicon characteristic requirements.

This driver has been developed together with Jorge Ramirez-Ortiz, and
is based on an RFC by Stephen Boyd[1], which in turn is based on work
by others on codeaurora.org[2].

[1] https://lkml.org/lkml/2015/9/18/833
[2] https://source.codeaurora.org/quic/la/kernel/msm-4.14/tree/drivers/regulator/cpr-regulator.c?h=msm-4.14

Changes since v6:
(Addressed comments from Ulf Hansson)
-Initialize mutex later.
-Take the mutex in cpr_pd_attach_dev(), in case we ever
implement async attach in the future.
-Add comment regarding why we get the cpu clock rate.
-Add comment how we handle unlisted frequencies.
-Clarify comment regarding why things related to virtual corners
are performed in cpr_pd_attach_dev().
-Removed the internal performance_state variable, the performance
state is instead calculated using the current corner pointer.
-Save a pointer to the first genpd dev that gets attached,
and use that rather than get_cpu_device(0), when getting the CPU
OPP table.

Niklas Cassel (5):
  dt-bindings: power: avs: Add support for CPR (Core Power Reduction)
  power: avs: Add support for CPR (Core Power Reduction)
  arm64: dts: qcom: qcs404: Add CPR and populate OPP table
  arm64: defconfig: enable CONFIG_QCOM_CPR
  arm64: defconfig: enable CONFIG_ARM_QCOM_CPUFREQ_NVMEM

 .../bindings/power/avs/qcom,cpr.txt           |  130 ++
 MAINTAINERS                                   |    8 +
 arch/arm64/boot/dts/qcom/qcs404.dtsi          |  132 +-
 arch/arm64/configs/defconfig                  |    2 +
 drivers/power/avs/Kconfig                     |   15 +
 drivers/power/avs/Makefile                    |    1 +
 drivers/power/avs/qcom-cpr.c                  | 1792 +++++++++++++++++
 7 files changed, 2072 insertions(+), 8 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/power/avs/qcom,cpr.txt
 create mode 100644 drivers/power/avs/qcom-cpr.c

-- 
2.23.0