linux-kernel - Re: [PATCH v7 3/3] arm64: dts: imx91: Add thermal-sensor and thermal-zone support

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Message-ID: <aQDwK5BL3tXp8EjY@lizhi-Precision-Tower-5810>
Date: Tue, 28 Oct 2025 12:32:43 -0400
From: Frank Li <Frank.li@....com>
To: Alberto Merciai <alb3rt0.m3rciai@...il.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Zhang Rui <rui.zhang@...el.com>, Lukasz Luba <lukasz.luba@....com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Pengfei Li <pengfei.li_1@....com>,
	Marco Felsch <m.felsch@...gutronix.de>, linux-pm@...r.kernel.org,
	devicetree@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	ye.li@....com, joy.zou@....com
Subject: Re: [PATCH v7 3/3] arm64: dts: imx91: Add thermal-sensor and
 thermal-zone support

On Wed, Oct 22, 2025 at 12:56:22PM +0200, Alberto Merciai wrote:
> On Mon, Oct 20, 2025 at 03:00:42PM -0400, Frank Li wrote:
> > Add thermal-sensor and thermal-zone support.
> >
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---
> > changes in v7
> > - new patch
> > ---
> >  arch/arm64/boot/dts/freescale/imx91.dtsi | 58 ++++++++++++++++++++++++++++++++
> >  1 file changed, 58 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/freescale/imx91.dtsi b/arch/arm64/boot/dts/freescale/imx91.dtsi
> > index 4d8300b2a7bca33bd0613db9e79d2fba6b40c052..f075592bfc01f1eb94d2a2bd8eea907cc2aed090 100644
> > --- a/arch/arm64/boot/dts/freescale/imx91.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/imx91.dtsi
> > @@ -6,6 +6,54 @@
> >  #include "imx91-pinfunc.h"
> >  #include "imx91_93_common.dtsi"
> >
> > +/{
> > +	thermal-zones {
> > +		cpu-thermal {
> > +			polling-delay-passive = <250>;
> > +			polling-delay = <2000>;
> > +			thermal-sensors = <&tmu 0>;
> > +
> > +			trips {
> > +				cpu_alert: cpu-alert {
> > +					temperature = <80000>;
> > +					hysteresis = <2000>;
> > +					type = "passive";
> > +				};
> > +
> > +				cpu_crit: cpu-crit {
> > +					temperature = <90000>;
> > +					hysteresis = <2000>;
> > +					type = "critical";
> > +				};
> > +			};
> > +
> > +			cooling-maps {
> > +				map0 {
> > +					trip = <&cpu_alert>;
> > +					cooling-device =
> > +						<&A55_0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> > +				};
> > +			};
> > +		};
> > +	};
> > +};
>
> Here you define cooling-maps with passive and critical trip points.
>
> I was trying test that by enabling CONFIG_THERMAL_EMULATION and setting
> the emulated temp via
>
> echo 85000 > /sys/class/thermal/thermal_zone0/emul_temp
>
> By checking with mhz (from lmbench Yocto recipe) command I was expecting that the 91 start
> throttling but is not the case, Am I missing something?

CPUfreq driver have not been implemented in upstream kernel. This don't
affect tmu driver, tmu driver focus on read CPU tempature.

Frank

>
> Thanks,
> Alberto