linux-kernel - Re: [RFC PATCH 3/3] arm64: dts: renesas: r9a09g047: Add thermal hotplug trip point

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Message-ID: <9b44d0ff-b28f-4d79-ad7b-b452db1db87a@arm.com>
Date: Tue, 11 Mar 2025 10:53:02 +0000
From: Christian Loehle <christian.loehle@....com>
To: John Madieu <john.madieu.xa@...renesas.com>, geert+renesas@...der.be,
 niklas.soderlund+renesas@...natech.se, conor+dt@...nel.org,
 krzk+dt@...nel.org, robh@...nel.org, rafael@...nel.org,
 daniel.lezcano@...aro.org
Cc: magnus.damm@...il.com, claudiu.beznea.uj@...renesas.com,
 devicetree@...r.kernel.org, john.madieu@...il.com, rui.zhang@...el.com,
 linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 biju.das.jz@...renesas.com, linux-pm@...r.kernel.org
Subject: Re: [RFC PATCH 3/3] arm64: dts: renesas: r9a09g047: Add thermal
 hotplug trip point

On 3/9/25 12:13, John Madieu wrote:
> Add CPU hotplug trip point to shutdown CPU1 and CPU2 when exceeding 110°C.
> 
> Signed-off-by: John Madieu <john.madieu.xa@...renesas.com>
> ---
>  arch/arm64/boot/dts/renesas/r9a09g047.dtsi | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/renesas/r9a09g047.dtsi b/arch/arm64/boot/dts/renesas/r9a09g047.dtsi
> index 93b57d7ad7b9..06bd394582e2 100644
> --- a/arch/arm64/boot/dts/renesas/r9a09g047.dtsi
> +++ b/arch/arm64/boot/dts/renesas/r9a09g047.dtsi
> @@ -533,6 +533,13 @@ map0 {
>  							 <&cpu2 0 3>, <&cpu3 0 3>;
>  					contribution = <1024>;
>  				};
> +
> +				map1 {
> +					trip = <&trip_emergency>;
> +					cooling-device = <&cpu1 0 1>, <&cpu2 0 1>;
> +					contribution = <1024>;
> +				};
> +
>  			};
>  
>  			trips {
> @@ -542,6 +549,12 @@ target: trip-point {
>  					type = "passive";
>  				};
>  
> +				trip_emergency: emergency {
> +					temperature = <110000>;
> +					hysteresis = <1000>;
> +					type = "plug";
> +				};
> +
>  				sensor_crit: sensor-crit {
>  					temperature = <120000>;
>  					hysteresis = <1000>;


Are there no other cooling methods?
How does it compare to idle inject?

Furthermore, couldn't the offlining of some CPUs lead to the rest being
operated at much higher OPPs therefore the overall power increase, too?
(Without having looked at if this is a possibility for this particular
SoC.)
Some numbers would be helpful IMO.