linux-kernel - Re: [PATCH 1/2] dt-bindings: clock: imx8m: introduce fsl,protected-clocks property

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Date:   Mon, 15 Aug 2022 15:57:56 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc:     abelvesa@...nel.org, abel.vesa@...aro.org, mturquette@...libre.com,
        sboyd@...nel.org, shawnguo@...nel.org, kernel@...gutronix.de,
        festevam@...il.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, linux-imx@....com,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Peng Fan <peng.fan@....com>
Subject: Re: [PATCH 1/2] dt-bindings: clock: imx8m: introduce
 fsl,protected-clocks property

Hi Peng,

On Mon, Aug 15, 2022 at 11:36:31AM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@....com>
> 
> i.MX8M Linux run on top of Jailhouse hypervisor, the root cell Linux
> should not disable clocks used by inmate. This would also benifit
> AMP to avoid Linux disable clocks used by Cortex-M4/M7.
> 
> So introduce fsl,protected-clocks for above case.
> 
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
>  Documentation/devicetree/bindings/clock/imx8m-clock.yaml | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/clock/imx8m-clock.yaml b/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> index 458c7645ee68..0ec490ff9a09 100644
> --- a/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> +++ b/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> @@ -39,6 +39,10 @@ properties:
>        ID in its "clocks" phandle cell. See include/dt-bindings/clock/imx8m-clock.h
>        for the full list of i.MX8M clock IDs.
>  
> +  fsl,protected-clocks:
> +    description: List of the Protected clock.
> +    $ref: /schemas/types.yaml#/definitions/uint32-array

There already is a generic protected-clocks property described in
https://github.com/devicetree-org/dt-schema/blob/0d1b78cd0c3d9a3d523ced17d7da64b03f6c18ea/dtschema/schemas/clock/clock.yaml#L131
We probably shouldn't add a property with the same name but different
meaning.

I am not sure if we want to go the route of a fsl specific property, it
looks like other SoCs could have similar problems and it might be worth
solving this problem with a broader view.

Anyway, please add a description to the binding what this property
actually does.

Sascha

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