Re: [PATCH v9 1/3] dt-bindings: thermal-zones: Document critical-action

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 01/10/2023 05:00, Fabio Estevam wrote:
> From: Fabio Estevam <festevam@denx.de>
> 
> Document the critical-action property to describe the thermal action
> the OS should perform after the critical temperature is reached.
> 
> The possible values are "shutdown" and "reboot".
> 
> The motivation for introducing the critical-action property is that
> different systems may need different thermal actions when the critical
> temperature is reached.
> 
> For example, a desktop PC may want the OS to trigger a shutdown
> when the critical temperature is reached.

 From my POV, 'critical' means kernel handles the action. We can not 
trust the userspace at this point.

The 'hot' trip point will result on a notification to the OS which can 
then take an last resort action before 'critical' kicks in (suspend, 
kill process, cpu hotplug, whatever)

> However, in some embedded cases, such behavior does not suit well,
> as the board may be unattended in the field and rebooting may be a
> better approach.
> 
> The bootloader may also benefit from this new property as it can check
> the SoC temperature and in case the temperature is above the critical
> point, it can trigger a shutdown or reboot accordingly.
> 
> Signed-off-by: Fabio Estevam <festevam@denx.de>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> ---
> Changes since v8:
> - Go back to putting critical-action as a thermal-zone property. (Daniel)
> 
>   .../devicetree/bindings/thermal/thermal-zones.yaml       | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
> index 4f3acdc4dec0..c2e4d28f885b 100644
> --- a/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
> +++ b/Documentation/devicetree/bindings/thermal/thermal-zones.yaml
> @@ -75,6 +75,15 @@ patternProperties:
>             framework and assumes that the thermal sensors in this zone
>             support interrupts.
>   
> +      critical-action:
> +        $ref: /schemas/types.yaml#/definitions/string
> +        description:
> +          The action the OS should perform after the critical temperature is reached.
> +
> +        enum:
> +          - shutdown
> +          - reboot
> +
>         thermal-sensors:
>           $ref: /schemas/types.yaml#/definitions/phandle-array
>           maxItems: 1

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