Hi folks,
Here's a second take on the cpufreq driver for Apple SoCs. This is a
complete rewrite using a stand-alone cpufreq driver instead of using the
cpufreq-dt infrastructure.
Since v1 we ran some experiments on the memory controller performance
switching and it turns out it doesn't make a huge difference, so it
makes sense to punt that feature to the future (perhaps once a proper
memory controller driver exists for other reasons, e.g. for error
handling).
One advantage of having a standalone cpufreq driver is that we can
support fast switching. This also means any future interaction with
the memory controller will probably use some bespoke mechanism instead
of the genpd infrastructure, so we can keep the fast path without
allowing sleeps/etc.
The driver is based on scpi-cpufreq.c, with some bits (e.g. the
apple,freq-domain stuff) inspired by how cpufreq-qcom-hw does it.
I'm not sure if that particular property should be described
in a binding, since it goes in the cpu nodes (qcom doesn't have it
anywhere...).
Changes since v1:
- Complete rewrite
- Reports current frequency to userspace properly (incl. if different
from requested due to hardware constraints)
- Supports fast switching
- MCC latency control stuff no longer included, punted for later
- Supports exposing higher states as turbo states
Hector Martin (4):
MAINTAINERS: Add entries for Apple SoC cpufreq driver
dt-bindings: cpufreq: apple,soc-cpufreq: Add binding for Apple SoC
cpufreq
cpufreq: apple-soc: Add new driver to control Apple SoC CPU P-states
arm64: dts: apple: Add CPU topology & cpufreq nodes for t8103
.../bindings/cpufreq/apple,soc-cpufreq.yaml | 121 +++++++
MAINTAINERS | 2 +
arch/arm64/boot/dts/apple/t8103.dtsi | 203 ++++++++++-
drivers/cpufreq/Kconfig.arm | 9 +
drivers/cpufreq/Makefile | 1 +
drivers/cpufreq/apple-soc-cpufreq.c | 330 ++++++++++++++++++
drivers/cpufreq/cpufreq-dt-platdev.c | 2 +
7 files changed, 658 insertions(+), 10 deletions(-)
create mode 100644 Documentation/devicetree/bindings/cpufreq/apple,soc-cpufreq.yaml
create mode 100644 drivers/cpufreq/apple-soc-cpufreq.c
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2.35.1
