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

From: Peter Geis <pgwipeout@gmail.com>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Robin Murphy <robin.murphy@arm.com>,
	Rob Herring <robh+dt@kernel.org>,
	Heiko Stuebner <heiko@sntech.de>,
	devicetree <devicetree@vger.kernel.org>,
	arm-mail-list <linux-arm-kernel@lists.infradead.org>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3] arm64: dts: rockchip: add thermal fan control to rockpro64
Date: Fri, 13 Aug 2021 11:10:20 -0400	[thread overview]
Message-ID: <CAMdYzYptXpahbcdkPm1C9_aH2khNtjdZyBmckndcWLnrh259QQ@mail.gmail.com> (raw)
In-Reply-To: <2b1050f2-0311-1871-820a-f876218894bc@linaro.org>

On Fri, Aug 13, 2021 at 10:54 AM Daniel Lezcano
<daniel.lezcano@linaro.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@gmail.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.

>
>
>
> --
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