linux-kernel - Re: [PATCH v3 4/8] dt-bindings: firmware: arm,scmi: Add atomic

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Message-ID: <681e31c1-54d8-8a3e-ff0f-683cd5156685@gmail.com>
Date:   Tue, 8 Feb 2022 08:12:39 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Cristian Marussi <cristian.marussi@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     sudeep.holla@....com, james.quinlan@...adcom.com,
        Jonathan.Cameron@...wei.com, etienne.carriere@...aro.org,
        vincent.guittot@...aro.org, souvik.chakravarty@....com,
        peter.hilber@...nsynergy.com, igor.skalkin@...nsynergy.com,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 4/8] dt-bindings: firmware: arm,scmi: Add
 atomic_threshold optional property



On 2/8/2022 7:44 AM, Cristian Marussi wrote:
> SCMI protocols in the platform can optionally signal to the OSPM agent
> the expected execution latency for a specific resource/operation pair.
> 
> Introduce an SCMI system wide optional property to describe a global time
> threshold which can be configured on a per-platform base to determine the
> opportunity, or not, for an SCMI command advertised to have a higher
> latency than the threshold, to be considered for atomic operations:
> high-latency SCMI synchronous commands should be preferably issued in the
> usual non-atomic mode.
> 
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Cristian Marussi <cristian.marussi@....com>
> ---
> v1 --> v2
> - rephrased the property description
> ---
>   .../devicetree/bindings/firmware/arm,scmi.yaml        | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> index eae15df36eef..646bdf2873b5 100644
> --- a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> +++ b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
> @@ -81,6 +81,15 @@ properties:
>     '#size-cells':
>       const: 0
>   
> +  atomic_threshold:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      An optional time value, expressed in microseconds, representing, on this
> +      platform, the threshold above which any SCMI command, advertised to have
> +      an higher-than-threshold execution latency, should not be considered for
> +      atomic mode of operation, even if requested.
> +      If left unconfigured defaults to zero.

Underscores in properties is not usually something that is desired, and 
it might be a good idea to put the unit in the property name, how about: 
atomic-threshold-us?

> +
>     arm,smc-id:
>       $ref: /schemas/types.yaml#/definitions/uint32
>       description:
> @@ -264,6 +273,8 @@ examples:
>               #address-cells = <1>;
>               #size-cells = <0>;
>   
> +            atomic_threshold = <10000>;
> +
>               scmi_devpd: protocol@11 {
>                   reg = <0x11>;
>                   #power-domain-cells = <1>;

-- 
Florian