linux-kernel - Re: [PATCH 1/2] dt-bindings: mfd: syscon: introduce no-auto-mmio property for syscons

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Message-ID: <20251029-ambiance-snooper-43dc00dcee68@spud>
Date: Wed, 29 Oct 2025 17:33:48 +0000
From: Conor Dooley <conor@...nel.org>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: mfd: syscon: introduce no-auto-mmio
 property for syscons

On Wed, Oct 29, 2025 at 08:27:05PM +0300, Dan Carpenter wrote:
> Generally, syscons are created automatically and accessed direclty via
> MMIO however sometimes syscons might only be accessible from the secure
> partition or through SCMI etc.  Introduce the no-auto-mmio property to
> tell the operating system that the syscon needs to be handled manually.

"System controller node represents a register region containing a set
of miscellaneous registers."

If this isn't actually a register region, but is instead an interface
provided by SCMI or whatever "secure partition" is (optee?), why is the
syscon compatible being used for the device in the first place?

Cheers,
Conor.

> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>  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 657c38175fba..a0ad12ae0bee 100644
> --- a/Documentation/devicetree/bindings/mfd/syscon.yaml
> +++ b/Documentation/devicetree/bindings/mfd/syscon.yaml
> @@ -245,6 +245,10 @@ properties:
>    resets:
>      maxItems: 1
>  
> +  no-auto-mmio:
> +    type: boolean
> +    description: Prevents the syscon from being created automatically
> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.51.0
> 

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