linux-kernel - Re: [PATCH 1/5] dt-bindings: mfd: syscon: Add mt8196 fdvfs syscons

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Message-ID: <4537173f-7f79-4629-a2ef-cbf1edd2ed81@collabora.com>
Date: Mon, 14 Jul 2025 10:47:32 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>,
 Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>,
 Hector Yuan <hector.yuan@...iatek.com>
Cc: kernel@...labora.com, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 1/5] dt-bindings: mfd: syscon: Add mt8196 fdvfs syscons

Il 11/07/25 16:57, Nicolas Frattaroli ha scritto:
> The MT8196 SoC uses two syscon ranges for CPU DVFS that are separate
> from each other. One, mt8196-fdvfs-config, is used to check for a magic
> number at that memory address to verify that fdvfs should be used. The
> other, mt8196-fdvfs, is used to configure the desired frequency for the
> DVFS controller for each CPU core.
> 

What is the reason why you're using syscons here?

Can't we simply assign the FDVFS MMIO to the cpufreq-hw node?

Or is there any reason why we can't declare it as mmio-sram? ...because I'm not
entirely sure but the FDVFS space should effectively be a [c]SRAM memory range...

Cheers,
Angelo

> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> ---
>   Documentation/devicetree/bindings/mfd/syscon.yaml | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mfd/syscon.yaml b/Documentation/devicetree/bindings/mfd/syscon.yaml
> index 27672adeb1fedb7c81b8ae86c35f4f3b26d5516f..5ee49d2ba0cdb72dd697a0fd71c8416ad4fd2c1e 100644
> --- a/Documentation/devicetree/bindings/mfd/syscon.yaml
> +++ b/Documentation/devicetree/bindings/mfd/syscon.yaml
> @@ -88,6 +88,8 @@ select:
>             - mediatek,mt8135-pctl-a-syscfg
>             - mediatek,mt8135-pctl-b-syscfg
>             - mediatek,mt8173-pctl-a-syscfg
> +          - mediatek,mt8196-fdvfs
> +          - mediatek,mt8196-fdvfs-config
>             - mediatek,mt8365-syscfg
>             - microchip,lan966x-cpu-syscon
>             - microchip,mpfs-sysreg-scb
> @@ -194,6 +196,8 @@ properties:
>             - mediatek,mt8135-pctl-a-syscfg
>             - mediatek,mt8135-pctl-b-syscfg
>             - mediatek,mt8173-pctl-a-syscfg
> +          - mediatek,mt8196-fdvfs
> +          - mediatek,mt8196-fdvfs-config
>             - mediatek,mt8365-infracfg-nao
>             - mediatek,mt8365-syscfg
>             - microchip,lan966x-cpu-syscon
>