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

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Message-ID: <20200824230956.GA3500214@bogus>
Date:   Mon, 24 Aug 2020 17:09:56 -0600
From:   Rob Herring <robh@...nel.org>
To:     Finley Xiao <finley.xiao@...k-chips.com>
Cc:     heiko@...ech.de, rui.zhang@...el.com, daniel.lezcano@...aro.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        huangtao@...k-chips.com, tony.xie@...k-chips.com, cl@...k-chips.com
Subject: Re: [PATCH v1] thermal/of: Introduce k-po, k-pu and k-i for a
 thermal zone

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@...k-chips.com>
> ---
>  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