Subject: Re: [PATCH 1/2] arm64: dts: rockchip: Fix multiple thermal zones conflict in rk3399.dtsi

From: Krzysztof Kozlowski <[email-masked]>
Date: Sun, 16 Jun 2019 11:31:27 +0200

On Fri, Jun 14, 2019 at 04:30:13PM +0200, Daniel Lezcano wrote:
> On 14/06/2019 16:02, Robin Murphy wrote:
> > On 14/06/2019 14:03, Daniel Lezcano wrote:
> >> On 14/06/2019 11:35, Heiko Stuebner wrote:
> >>> Hi Daniel,
> >>>
> >>> Am Dienstag, 4. Juni 2019, 18:57:57 CEST schrieb Daniel Lezcano:
> >>>> Currently the common thermal zones definitions for the rk3399 assumes
> >>>> multiple thermal zones are supported by the governors. This is not the
> >>>> case and each thermal zone has its own governor instance acting
> >>>> individually without collaboration with other governors.
> >>>>
> >>>> As the cooling device for the CPU and the GPU thermal zones is the
> >>>> same, each governors take different decisions for the same cooling
> >>>> device leading to conflicting instructions and an erratic behavior.
> >>>>
> >>>> As the cooling-maps is about to become an optional property, let's
> >>>> remove the cpu cooling device map from the GPU thermal zone.
> >>>>
> >>>> Signed-off-by: Daniel Lezcano <[email-masked]>
> >>>> ---
> >>>>   arch/arm64/boot/dts/rockchip/rk3399.dtsi | 9 ---------
> >>>>   1 file changed, 9 deletions(-)
> >>>>
> >>>> diff --git a/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> >>>> b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> >>>> index 196ac9b78076..e1357e0f60f7 100644
> >>>> --- a/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> >>>> +++ b/arch/arm64/boot/dts/rockchip/rk3399.dtsi
> >>>> @@ -821,15 +821,6 @@
> >>>>                       type = "critical";
> >>>>                   };
> >>>>               };
> >>>> -
> >>>> -            cooling-maps {
> >>>> -                map0 {
> >>>> -                    trip = <&gpu_alert0>;
> >>>> -                    cooling-device =
> >>>> -                        <&cpu_b0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> >>>> -                        <&cpu_b1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> >>>> -                };
> >>>> -            };
> >>>>           };
> >>>>       };
> >>>
> >>> my knowledge of the thermal framework is not that big, but what about
> >>> the
> >>> rk3399-devices which further detail the cooling-maps like
> >>> rk3399-gru-kevin
> >>> and the rk3399-nanopc-t4 with its fan-handling in the cooling-maps?
> >>
> >> The rk3399-gru-kevin is correct.
> >>
> >> The rk3399-nanopc-t4 is not correct because the cpu and the gpu are
> >> sharing the same cooling device (the fan). There are different
> >> configurations:
> >>
> >> 1. The cpu cooling device for the CPU and the fan for the GPU
> >>
> >> 2. Different trip points on the CPU thermal zone, eg. one to for the CPU
> >> cooling device and another one for the fan.
> >>
> >> There are some variant for the above. If this board is not on battery,
> >> you may want to give priority to the throughput, so activate the fan
> >> first and then cool down the CPU. Or if you are on battery, you may want
> >> to invert the trip points.
> >>
> >> In any case, it is not possible to share the same cooling device for
> >> different thermal zones.
> > 
> > OK, thanks for the clarification. I'll get my board set up again to
> > figure out the best fix for rk3399-nanopc-t4 (FWIW most users are
> > probably just using passive cooling or a plain DC fan anyway). You might
> > want to raise this issue with the maintainers of
> > arch/arm/boot/dts/exynos5422-odroidxu3-common.dtsi, since the
> > everything-shared-by-everything approach in there was what I used as a
> > reference.
> 
> Cc'ed: Kukjin Kim and Krzysztof Kozlowski
> 
> Easy :)
>

Assuming that all trip-points are the same between thermal zones, I
understand that solution could be to have one thermal zone with thermal
multiple sensors (some time ago bindings did not support it) and all
cooling devices? Then only one governor would be assigned?

Best regards,
Krzysztof

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