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Message-ID: <861qqxocal.wl-maz@kernel.org>
Date: Mon, 24 Oct 2022 09:28:50 +0100
From: Marc Zyngier <maz@...nel.org>
To: Hector Martin <marcan@...can.st>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Matthias Brugger <matthias.bgg@...il.com>,
Sven Peter <sven@...npeter.dev>,
Alyssa Rosenzweig <alyssa@...enzweig.io>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Stephen Boyd <sboyd@...nel.org>,
Ulf Hansson <ulf.hansson@...aro.org>,
Mark Kettenis <mark.kettenis@...all.nl>, asahi@...ts.linux.dev,
linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/5] Apple SoC cpufreq driver
On Mon, 24 Oct 2022 05:39:20 +0100,
Hector Martin <marcan@...can.st> wrote:
>
> Hi folks,
>
> Third time's the charm? Here's v3 of the cpufreq driver for Apple SoCs.
> This version takes a page from both v1 and v2, keeping the dedicated
> cpufreq style (instead of pretending to be a clock controller) but using
> dedicated DT nodes for each cluster, which accurately represents the
> hardware. In particular, this makes supporting t6002 (M1 Ultra) a lot
> more reasonable on the DT side.
>
> This version also switches to the standard performance-domains binding,
> so we don't need any more vendor-specific properties. In order to
> support this, I had to make the performance-domains parsing code more
> generic. This required a minor change to the only consumer
> (mediatek-cpufreq-hw).
>
> The Linux driver probes based on platform compatible, and then attempts
> to locate the cluster nodes by following the performance-domains links
> from CPU nodes (this will then fail for any incompatible nodes, e.g. if
> a future SoC needs a new compatible and can't fall back). This approach
> was suggested by robh as the right way to handle the impedance mismatch
> between the hardware, which has separate controllers per cluster, and
> the Linux model where there can only be one CPUFreq driver instance.
>
> Functionality-wise, there are no significant changes from v2. The only
> notable difference is support for t8112 (M2). This works largely the
> same as the other SoCs, but they ran out of bits in the current PState
> register, so that needs a SoC-specific quirk. Since that register is
> not used by macOS (it was discovered experimentally) and is not critical
> for functionality (it just allows accurately reporting the current
> frequency to userspace, given boost clock limitations), I've decided to
> only use it when a SoC-specific compatible is present. The default
> fallback code will simply report the requested frequency as actual.
> I expect this will work for future SoCs.
>
> As usual, MAINTAINERS and DT changes are split. I expect patches #2~#4
> to go through the cpufreq tree, and we'll take care of #1 and #5 via
> the asahi-soc tree.
>
> Hector Martin (5):
> MAINTAINERS: Add entries for Apple SoC cpufreq driver
> dt-bindings: cpufreq: apple,soc-cpufreq: Add binding for Apple SoC
> cpufreq
> cpufreq: Generalize of_perf_domain_get_sharing_cpumask phandle format
> cpufreq: apple-soc: Add new driver to control Apple SoC CPU P-states
> arm64: dts: apple: Add CPU topology & cpufreq nodes for t8103
>
> .../cpufreq/apple,cluster-cpufreq.yaml | 119 ++++++
> MAINTAINERS | 2 +
> arch/arm64/boot/dts/apple/t8103.dtsi | 206 +++++++++-
> drivers/cpufreq/Kconfig.arm | 9 +
> drivers/cpufreq/Makefile | 1 +
> drivers/cpufreq/apple-soc-cpufreq.c | 352 ++++++++++++++++++
> drivers/cpufreq/cpufreq-dt-platdev.c | 2 +
> drivers/cpufreq/mediatek-cpufreq-hw.c | 14 +-
> include/linux/cpufreq.h | 28 +-
> 9 files changed, 706 insertions(+), 27 deletions(-)
> create mode 100644 Documentation/devicetree/bindings/cpufreq/apple,cluster-cpufreq.yaml
> create mode 100644 drivers/cpufreq/apple-soc-cpufreq.c
FWIW, and for the whole series:
Acked-by: Marc Zyngier <maz@...nel.org>
M.
--
Without deviation from the norm, progress is not possible.
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