Aw: Re: [PATCH] Fix mt7622.dtsi thermal cpu

[Daniel Lezcano]

Hi Frank,

On 25/06/2021 10:16, Frank Wunderlich wrote:
> Hi,
> 

>> Gesendet: Donnerstag, 24. Juni 2021 um 15:29 Uhr Von: "Eric
>> Woudstra" <ericwouds at gmail.com> The SOC runs unthrotlled slowly to
>> 80 degrees. This takes minutes.
Polling interval 1 second or less does not matter much when looking at
these temperature rise times
>> 
>> After that in more then an hour it slowly creeps up to 85. I
>> believe
the design is so that the SOC, under normal circumstances, can run at
1.35 GHz without throttling frequency, without heatsink. It just needs a
safeguard for different circumstances.
>> 
>> Most of these SOCs can also run in industrial grade circumstances,
which means up to 85 degrees ambient temperature already . If not
industrial then this would be 60 degrees ambient already
>> 
>> But only someone at Mediatek can confirm this
> 
> maybe Matthias knows anybody? get_maintainers-script shows no mtk
> employee for mtk_thermal driver,
added Sean and Ryder as common Linux-Contacts...
> 
> Daniel from openwrt have some other mt7622 Boards maybe he can test
the Fan approach below
> 
>> On Jun 24, 2021, 12:21 PM, at 12:21 PM, Daniel Lezcano
<daniel.lezcano at linaro.org> wrote:
>>> Found that:
>>> 
>>> 
https://download.kamami.pl/p579344-MT7622A_Datasheet_for_BananaPi_Only%281%29.pdf
>>> 
>>> Chapter 3.3 - Thermal Characteristics
>>> 
>>> Given the values I suggest:
>>> 
>>> - Passive - 80°C
>>> 
>>> - Hot - 90°C
>>> 
>>> - Critical - 100°C
> 
> maybe adding FAN (r64, don't know for other mt7622 boards) for lower
> 2
trips (with adjusted temperature points) and cpu-throtteling for upper 2
trips

It depends what you want to achieve first:

 - better / sustained performance, then fan before

 - quiet device or power saving (on battery) then cpu throttling before

That is board specific, it should be tuned on DT board specific file.

Some comments below:

> something like this (used the 70/80 trip points discussed before):
> --- a/arch/arm64/boot/dts/mediatek/mt7622.dtsi
> +++ b/arch/arm64/boot/dts/mediatek/mt7622.dtsi

You should not add the fan in the mt7622.dtsi itself but in the board
specific file where there is a fan output on it. mt7622.dtsi is supposed
to be the SoC itself AFAICT.

For instance:

https://git.kernel.org/pub/scm/linux/kernel/git/thermal/linux.git/tree/arch/arm64/boot/dts/rockchip/rk3399-sapphire.dtsi#n39

https://git.kernel.org/pub/scm/linux/kernel/git/thermal/linux.git/tree/arch/arm64/boot/dts/rockchip/rk3399-sapphire.dtsi#n164

> @@ -134,6 +134,13 @@
>  		};
>  	};
>  
> +	fan0: pwm-fan {
> +		compatible = "pwm-fan";
> +		#cooling-cells = <2>;
> +		pwms = <&pwm 2 10000 0>;
> +		cooling-levels = <0 102 170 230>;
> +	};
> +
>  	thermal-zones {
>  		cpu_thermal: cpu-thermal {
>  			polling-delay-passive = <1000>;
> @@ -143,13 +150,13 @@
>  
>  			trips {
>  				cpu_passive: cpu-passive {
> -					temperature = <47000>;
> +					temperature = <70000>;
>  					hysteresis = <2000>;
>  					type = "passive";
>  				};
>  
>  				cpu_active: cpu-active {
> -					temperature = <67000>;
> +					temperature = <80000>;
>  					hysteresis = <2000>;
>  					type = "active";
>  				};
> @@ -170,14 +177,12 @@
>  			cooling-maps {
>  				map0 {
>  					trip = <&cpu_passive>;
> -					cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> -							 <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> +					cooling-device = <&fan0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
>  				};

fan == active trip point

This is referring to the passive trip point. So it should point to the
CPU as it is now. Note the order of mitigation is inverted regarding the
proposal description.

>  				map1 {
>  					trip = <&cpu_active>;
> -					cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> -							 <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> +					cooling-device = <&fan0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
>  				};
>  
>  				map2 {
> @@ -428,6 +433,7 @@
>  	pwm: pwm at 11006000 {
>  		compatible = "mediatek,mt7622-pwm";
>  		reg = <0 0x11006000 0 0x1000>;
> +		#pwm-cells = <3>;
>  		interrupts = <GIC_SPI 77 IRQ_TYPE_LEVEL_LOW>;
>  		clocks = <&topckgen CLK_TOP_PWM_SEL>,
>  			 <&pericfg CLK_PERI_PWM_PD>,
> 
> 
> regards Frank
> 


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