linux-kernel - Re: [PATCH v2 1/4] dt-bindings: cpufreq: Add mediatek,mt8196-cpufreq-hw binding

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Message-ID: <20250715034904.GA4699-robh@kernel.org>
Date: Mon, 14 Jul 2025 22:49:04 -0500
From: Rob Herring <robh@...nel.org>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>, kernel@...labora.com,
	linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH v2 1/4] dt-bindings: cpufreq: Add
 mediatek,mt8196-cpufreq-hw binding

On Mon, Jul 14, 2025 at 04:41:30PM +0200, AngeloGioacchino Del Regno wrote:
> Il 14/07/25 16:08, Nicolas Frattaroli ha scritto:
> > The MediaTek MT8196 SoC has new cpufreq hardware, with added memory
> > register ranges to control Dynamic-Voltage-Frequency-Scaling.
> > 
> > The DVFS hardware is controlled through a set of registers referred to
> > as "FDVFS"; one is a location from which a magic number is read to
> > ensure DVFS should be used, the other is a region to set the desired
> > target frequency that DVFS should aim towards for each performance
> > domain.
> > 
> > Instead of working around the old binding and its already established
> > meanings for the reg items, add a new binding. The FDVFS register memory
> > regions are at the beginning, which allows us to easily expand this
> > binding for future SoCs which may have more than 3 performance domains.
> > 
> > Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> > ---
> >   .../cpufreq/mediatek,mt8196-cpufreq-hw.yaml        | 86 ++++++++++++++++++++++
> >   1 file changed, 86 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/cpufreq/mediatek,mt8196-cpufreq-hw.yaml b/Documentation/devicetree/bindings/cpufreq/mediatek,mt8196-cpufreq-hw.yaml
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..26bf21e05888646b4d1bdac95bfba0f36e037ffd
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/cpufreq/mediatek,mt8196-cpufreq-hw.yaml
> > @@ -0,0 +1,86 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/cpufreq/mediatek,mt8196-cpufreq-hw.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: MediaTek CPUFreq for MT8196 and related SoCs
> 
> title: MediaTek Hybrid CPUFreq for MT8196/MT6991 series SoCs
> 
> > +
> > +maintainers:
> > +  - Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> > +
> > +description:
> > +  MT8196 uses CPUFreq management hardware that supports dynamic voltage
> > +  frequency scaling (dvfs), and can support several performance domains.
> > +
> > +properties:
> > +  compatible:
> > +    const: mediatek,mt8196-cpufreq-hw
> > +
> > +  reg:
> > +    items:
> > +      - description: FDVFS magic number register region
> 
> As already said in the other commit, we might just be able to avoid adding the
> magic number register region :-)
> 
> > +      - description: FDVFS control register region
> > +      - description: OPP tables and control for performance domain 0
> > +      - description: OPP tables and control for performance domain 1
> > +      - description: OPP tables and control for performance domain 2
> > +
> > +  "#performance-domain-cells":
> > +    description:
> > +      Number of cells in a performance domain specifier. Must be 1.
> 
> The description is redundant and doesn't add any real information, I think you
> should drop it.
> 
> Bindings maintainers, please, opinions?

Drop.

Rob