Re: [PATCH v1] thermal/of: Introduce k-po, k-pu and k-i for a thermal zone

From: Rob Herring
Date: Mon Aug 24 2020 - 19:10:02 EST


On Tue, Aug 11, 2020 at 08:31:15PM +0800, Finley Xiao wrote:
> The default value for k_pu is:
> 2 * sustainable_power / (desired_temperature - switch_on_temp)
> The default value for k_po is:
> sustainable_power / (desired_temperature - switch_on_temp)
> The default value for k_i is 10.
>
> Even though these parameters of the PID controller can be changed
> by the following sysfs files:
> /sys/class/thermal/thermal_zoneX/k_pu
> /sys/class/thermal/thermal_zoneX/k_po
> /sys/class/thermal/thermal_zoneX/k_i
>
> But it's still more convenient to change the default values by devicetree,
> so introduce these three optional properties. If provided these properties,
> they will be parsed and associated with the thermal zone via the thermal
> zone parameters.
>
> Signed-off-by: Finley Xiao <finley.xiao@xxxxxxxxxxxxxx>
> ---
> Documentation/devicetree/bindings/thermal/thermal.txt | 14 ++++++++++++++

Bindings should be a separate file and this one is a DT schema now.

> drivers/thermal/thermal_of.c | 7 +++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/thermal/thermal.txt b/Documentation/devicetree/bindings/thermal/thermal.txt
> index f78bec19ca35..ebe936b57ded 100644
> --- a/Documentation/devicetree/bindings/thermal/thermal.txt
> +++ b/Documentation/devicetree/bindings/thermal/thermal.txt
> @@ -165,6 +165,20 @@ Optional property:
> 2000mW, while on a 10'' tablet is around
> 4500mW.
>
> +- k-po: Proportional parameter of the PID controller when
> + current temperature is above the target.
> + Type: signed
> + Size: one cell
> +
> +- k-pu: Proportional parameter of the PID controller when
> + current temperature is below the target.
> + Type: signed
> + Size: one cell
> +
> +- k-i: Integral parameter of the PID controller.
> + Type: signed
> + Size: one cell

What's PID?

I know nothing about the sysfs params, but the binding needs to stand on
it's own and needs enough detail to educate me.

Rob