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Subject: Re: [PATCH 1/8] arm64: dts: mt8183: add thermal zone node
To:     Matthias Kaehlcke <mka@chromium.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>
Cc:     "michael.kao" <michael.kao@mediatek.com>, fan.chen@mediatek.com,
        jamesjj.liao@mediatek.com, dawei.chien@mediatek.com,
        louis.yu@mediatek.com, roger.lu@mediatek.com,
        Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        devicetree@vger.kernel.org, linux-mediatek@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-pm@vger.kernel.org
References: <1556793795-25204-1-git-send-email-michael.kao@mediatek.com>
 <1556793795-25204-2-git-send-email-michael.kao@mediatek.com>
 <CAJMQK-isJf6f+OubbCdoXs8L2cup=rm3Z8Mr7Q26QshMP-0wxA@mail.gmail.com>
 <20190503164651.GB40515@google.com>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <c6cf6170-331d-8ffc-d272-e5d8ee648eda@linaro.org>
Date:   Mon, 6 May 2019 12:43:39 +0200
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On 03/05/2019 18:46, Matthias Kaehlcke wrote:
> Hi,
> 
> On Fri, May 03, 2019 at 04:03:58PM +0800, Hsin-Yi Wang wrote:
>> On Thu, May 2, 2019 at 10:43 AM michael.kao <michael.kao@mediatek.com> wrote:
>>>
>>> Add thermal zone node to Mediatek MT8183 dts file.
>>>
>>> Signed-off-by: Michael Kao <michael.kao@mediatek.com>
>>> ---
>>>  arch/arm64/boot/dts/mediatek/mt8183.dtsi | 64 ++++++++++++++++++++++++++++++++
>>>  1 file changed, 64 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/mediatek/mt8183.dtsi b/arch/arm64/boot/dts/mediatek/mt8183.dtsi
>>> index 926df75..b92116f 100644
>>> --- a/arch/arm64/boot/dts/mediatek/mt8183.dtsi
>>> +++ b/arch/arm64/boot/dts/mediatek/mt8183.dtsi
>>> @@ -334,6 +334,67 @@
>>>                         status = "disabled";
>>>                 };
>>>
>>> +               thermal: thermal@1100b000 {
>>> +                       #thermal-sensor-cells = <1>;
>>> +                       compatible = "mediatek,mt8183-thermal";
>>> +                       reg = <0 0x1100b000 0 0x1000>;
>>> +                       interrupts = <0 76 IRQ_TYPE_LEVEL_LOW>;
>>> +                       clocks = <&infracfg CLK_INFRA_THERM>,
>>> +                                <&infracfg CLK_INFRA_AUXADC>;
>>> +                       clock-names = "therm", "auxadc";
>>> +                       resets = <&infracfg  MT8183_INFRACFG_AO_THERM_SW_RST>;
>>> +                       mediatek,auxadc = <&auxadc>;
>>> +                       mediatek,apmixedsys = <&apmixedsys>;
>>> +                       mediatek,hw-reset-temp = <117000>;
>>> +                       nvmem-cells = <&thermal_calibration>;
>>> +                       nvmem-cell-names = "calibration-data";
>>> +               };
>>> +
>>> +               thermal-zones {
>>> +                       cpu_thermal: cpu_thermal {
>>> +                               polling-delay-passive = <1000>;
>>> +                               polling-delay = <1000>;
>>> +
>>> +                               thermal-sensors = <&thermal 0>;
>>> +                               sustainable-power = <1500>;
>>> +                       };
>>> +
>>> +                       tzts1: tzts1 {
>>> +                               polling-delay-passive = <1000>;
>>> +                               polling-delay = <1000>;
>>> +                               thermal-sensors = <&thermal 1>;
>> Is sustainable-power required for tzts? Though it's an optional
>> property, kernel would have warning:
>> [    0.631556] thermal thermal_zone1: power_allocator:
>> sustainable_power will be estimated
>> [    0.639586] thermal thermal_zone2: power_allocator:
>> sustainable_power will be estimated
>> [    0.647611] thermal thermal_zone3: power_allocator:
>> sustainable_power will be estimated
>> [    0.655635] thermal thermal_zone4: power_allocator:
>> sustainable_power will be estimated
>> [    0.663658] thermal thermal_zone5: power_allocator:
>> sustainable_power will be estimated
>> if no sustainable-power assigned.
> 
> The property is indeed optional, if it isn't specified IPA will use
> the sum of the minimum power of all 'power actors' of the zone as
> estimate (see estimate_sustainable_power()). This may lead to overly
> agressive throttling, since the nominal sustainable power will always
> be <= the requested power.
> 
> In my understanding the sustainable power may varies between devices,
> even for the same SoC. One could have all the hardware crammed into a
> tiny plastic enclosure (e.g. ASUS Chromebit), another might have a
> laptop form factor and a metal enclosure (e.g. ASUS C201). Both
> examples are based on an Rockchip rk3288, but they have completely
> different thermal behavior, and would likely have different values for
> 'sustainable-power'.
> 
> In this sense I tend to consider 'sustainable-power' more a device,
> than a SoC property. You could specify a 'reasonable' value as a
> starting point, but it will likely not be optimal for all or even most
> devices. The warning might even be useful for device makers by
> indicating them that there is room for tweaking.


The sustainable power is the power dissipated by the devices belonging
to the thermal zone at the given trip temperature.

With the power numbers and the cooling devices, the IPA will change the
states of the cooling devices to leverage the dissipated power to the
sustainable power.

The contribution is the cooling effect of the cooling device.

However, the IPA is limited to one thermal zone and the cooling device
is the cpu cooling device. There is the devfreq cooling device but as
the graphic driver is not upstream, it is found in the android tree only
for the moment.

As you mentioned the sustainable power can vary depending on the form
factor and the production process for the same SoC (they can go to
higher frequencies thus dissipate more power). That is the reason why we
split the DT per SoC and we override the values on a per SoC version basis.

You can have a look the rk3399.dtsi and their variant for experimental
board (*-rock960.dts) and the chromebook version (*-gru-kevin.dts).

Do you want a empiric procedure to find out the sustainable power ?


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