Re: [Query] thermal: Who is using "cooling-{min|max}-level}" properties ?

From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Zhang Rui <rui.zhang@intel.com>,
	Eduardo Valentin <edubezval@gmail.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	linux-pm@vger.kernel.org, robh+dt@kernel.org,
	devicetree@vger.kernel.org, Punit.Agrawal@arm.com,
	ionela.voinescu@arm.com
Subject: Re: [Query] thermal: Who is using "cooling-{min|max}-level}" properties ?
Date: Wed, 7 Feb 2018 11:45:31 +0100	[thread overview]
Message-ID: <11fbba25-7029-8a13-476e-ea2f2de6fbf9@linaro.org> (raw)
In-Reply-To: <20180207102446.GS28462@vireshk-i7>

On 07/02/2018 11:24, Viresh Kumar wrote:
> On 07-02-18, 11:04, Daniel Lezcano wrote:
>> Yeah, this is a bit fuzzy. There are still cooling-{min|max}-*state*
>> definitions in the DTs
>>
>> Documentation/devicetree/bindings/hwmon/pwm-fan.txt:
>> cooling-min-state = <0>;
>> arch/arm/boot/dts/exynos4412-odroidu3.dts:
>> cooling-min-state = <0>;
>> arch/arm/boot/dts/exynos5410-odroidxu.dts:
>> cooling-min-state = <0>;
>> arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi:
>> cooling-min-state = <0>;
>> arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi:
>> cooling-min-state = <0>;
>>
>>
>> IIUC, the cooling-device in the mapping defines the min and max states
>> which are the values used in the thermal zone binding.
>>
>> And the cooling-[min|max]-level are the hardware limits:
>>
>> cooling-min-level <= cooling-device min|max state <= cooling-max-level
>>
>> For example on the hikey6220:
>>
>> The DT specifies for CPU0:
>>
>> 	operating-points-v2 = <&cpu_opp_table>;
>> 	cooling-min-level = <4>;
>> 	cooling-max-level = <0>;
>> 	#cooling-cells = <2>; /* min followed by max */
>>
>> and for the cooling device for map0
>>
>> 	cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
>>
>> So if my understanding is correct, the optional property
>> cooling-[min|max]-level is used to make sure the cooling device min
>> state and max state are in the hardware boundaries. And the thermal
>> framework misses to do the consistency check at init.
>>
>> I'm not sure how useful are cooling-{min|max}-*state* bindings.

I meant here cooling-{min|max}-*level*

> Okay, but we aren't validating it this way in code. Isn't it ?

Yes, that is my understanding. cooling-min-level and cooling-max-level
are not used in the thermal framework code today.

So if they are defined, we should check the cooling-device max and min
are in the boundaries (if they are different from no-limit).

That needs confirmation from the maintainers, I'm not 100% sure.

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