linux-kernel - Re: [PATCH v2 2/5] arm64: dts: rockchip: Add powerzones definition for rock960

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Date:   Wed, 8 Dec 2021 17:16:18 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     arnd@...aro.org, heiko@...ech.de, ulf.hansson@...aro.org,
        rjw@...ysocki.net, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        lukasz.luba@....com, Robin Murphy <robin.murphy@....com>,
        Johan Jonker <jbx6244@...il.com>,
        Helen Koike <helen.koike@...labora.com>,
        Brian Norris <briannorris@...omium.org>,
        Shunqian Zheng <zhengsq@...k-chips.com>,
        Elaine Zhang <zhangqing@...k-chips.com>,
        "moderated list:ARM/Rockchip SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC support" 
        <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH v2 2/5] arm64: dts: rockchip: Add powerzones definition
 for rock960


Hi Rob,

On 07/12/2021 19:41, Rob Herring wrote:

[ ... ]

>>         thermal_zones: thermal-zones {
>>                 cpu_thermal: cpu-thermal {
>>                         polling-delay-passive = <100>;
>> @@ -2027,6 +2050,8 @@ gpu: gpu@...a0000 {
>>                 clocks = <&cru ACLK_GPU>;
>>                 #cooling-cells = <2>;
>>                 power-domains = <&power RK3399_PD_GPU>;
>> +               #powerzone-cells = <0>;
>> +               powerzone = <&PKG_PZ>;
> 
> Every CPU and the GPU are in the same powerzone. What is the point? Do
> you really have to be told that CPUs and GPU are a source of heat and
> might need to be limited?

A powerzone ==> can read power && set power limit

Every CPU is a powerzone as well as the GPU.

They are all grouped under PKG_PZ.

That means we have:

 pkg
  |-- cpu0-3
  |
  |-- cpu4-7
  |
  `-- gpu

We can read the power consumption of cpu0-3, cpu4-7 or gpu and set their
power limit.

We can read the power consumption of pkg (which is the sum of the power
consumption of cpu0-3, cpu4-7 and gpu) and I can set the power limit
which will ensure powerof(cpu0-3 + cpu4-7 + gpu) <= powerof(pkg).



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