linux-kernel - Re: [PATCH v3] arm64: dts: rockchip: add thermal fan control to rockpro64

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Date:   Fri, 13 Aug 2021 17:46:16 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Peter Geis <pgwipeout@...il.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        devicetree <devicetree@...r.kernel.org>,
        arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] arm64: dts: rockchip: add thermal fan control to
 rockpro64

On 13/08/2021 17:10, Peter Geis wrote:
> On Fri, Aug 13, 2021 at 10:54 AM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
>>
>>
>> Hi Robin,
>>
>>
>> On 13/08/2021 15:51, Robin Murphy wrote:
>>> On 2021-08-13 13:59, Daniel Lezcano wrote:
>>>> On 30/07/2021 17:17, Peter Geis wrote:
>>>>> The rockpro64 had a fan node since
>>>>> commit 5882d65c1691 ("arm64: dts: rockchip: Add PWM fan for RockPro64")
>>>>> however it was never tied into the thermal driver for automatic control.
>>>>>
>>>>> Add the links to the thermal node to permit the kernel to handle this
>>>>> automatically.
>>>>> Borrowed from the (rk3399-khadas-edge.dtsi).
>>>>>
>>>>> Signed-off-by: Peter Geis <pgwipeout@...il.com>
>>
>> [ ... ]
>>
>>>>>   +&cpu_thermal {
>>>>> +    trips {
>>>>> +        cpu_warm: cpu_warm {
>>>>> +            temperature = <55000>;
>>>>> +            hysteresis = <2000>;
>>>>> +            type = "active";
>>>>> +        };
>>>>> +
>>>>> +        cpu_hot: cpu_hot {
>>>>> +            temperature = <65000>;
>>>>> +            hysteresis = <2000>;
>>>>> +            type = "active";
>>>>> +        };
>>>>> +    };
>>>>> +
>>>>
>>>> Why two trip points ?
>>>>
>>>> Why not one functioning temperature and no lower / upper limits for the
>>>> cooling maps ?
>>>
>>> Certainly when I first did this for NanoPC-T4, IIRC it was to avoid the
>>> fan ramping up too eagerly, since level 1 for my fan is effectively
>>> silent but still cools enough to let a moderate load eventually settle
>>> to a steady state below the second trip.
> 
> That's the same issue I had on the rockpro64.
> 
>>
>> Thanks for your answer.
>>
>> What would be the governor for this setup ?
>>
> 
> The default governor when using arm64_defconfig is step_wise.

Ok, thanks


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