Re: [PATCH v4 4/6] arm64: dts: meson: sei510: Add minimal thermal zone

[Amit Kucheria <amit.kucheria@linaro.org>]

On Thu, Aug 22, 2019 at 4:59 AM Kevin Hilman <khilman@baylibre.com> wrote:
>
> Guillaume La Roque <glaroque@baylibre.com> writes:
>
> > Add minimal thermal zone for two temperature sensor
> > One is located close to the DDR and the other one is
> > located close to the PLLs (between the CPU and GPU)
> >
> > Signed-off-by: Guillaume La Roque <glaroque@baylibre.com>
> > Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> > ---
> >  .../boot/dts/amlogic/meson-g12a-sei510.dts    | 70 +++++++++++++++++++
> >  1 file changed, 70 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/amlogic/meson-g12a-sei510.dts b/arch/arm64/boot/dts/amlogic/meson-g12a-sei510.dts
> > index c9fa23a56562..35d2ebbd6d4e 100644
> > --- a/arch/arm64/boot/dts/amlogic/meson-g12a-sei510.dts
> > +++ b/arch/arm64/boot/dts/amlogic/meson-g12a-sei510.dts
> > @@ -10,6 +10,7 @@
> >  #include <dt-bindings/input/input.h>
> >  #include <dt-bindings/gpio/meson-g12a-gpio.h>
> >  #include <dt-bindings/sound/meson-g12a-tohdmitx.h>
> > +#include <dt-bindings/thermal/thermal.h>
> >
> >  / {
> >       compatible = "seirobotics,sei510", "amlogic,g12a";
> > @@ -33,6 +34,67 @@
> >               ethernet0 = &ethmac;
> >       };
> >
> > +     thermal-zones {
> > +             cpu-thermal {
> > +                     polling-delay = <1000>;
> > +                     polling-delay-passive = <100>;
> > +                     thermal-sensors = <&cpu_temp>;
> > +
> > +                     trips {
> > +                             cpu_hot: cpu-hot {
> > +                                     temperature = <85000>; /* millicelsius */
> > +                                     hysteresis = <2000>; /* millicelsius */
> > +                                     type = "hot";
> > +                             };

No passive trip point? That is where the cooling-maps are really useful.

> > +
> > +                             cpu_critical: cpu-critical {
> > +                                     temperature = <110000>; /* millicelsius */
> > +                                     hysteresis = <2000>; /* millicelsius */
> > +                                     type = "critical";
> > +                             };
> > +                     };
> > +

I think, what you really want is to change your hot trip point above
to passive. And if you need another trip before that (to send
notification to userspace, for example), just add another hot trip
point at a lower temperature.

> > +                     cooling-maps {
> > +                             map0 {
> > +                                     trip = <&cpu_hot>;
> > +                                     cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > +                                                      <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > +                                                      <&cpu2 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > +                                                      <&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> > +                             };
> > +
> > +                             map1 {
> > +                                     trip = <&cpu_critical>;
> > +                                     cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > +                                                      <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > +                                                      <&cpu2 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
> > +                                                      <&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> > +                             };

The cooling-map associated with a critical trip point is of no use in
my experience because the device is already on its way to shutting
down then.

> > +                     };
> > +             };
> > +
> > +             ddr-thermal {
> > +                     polling-delay = <1000>;
> > +                     polling-delay-passive = <100>;
> > +                     thermal-sensors = <&ddr_temp>;
> > +
> > +                     trips {
> > +                             ddr_critical: ddr-critical {
> > +                                     temperature = <110000>; /* millicelsius */
> > +                                     hysteresis = <2000>; /* millicelsius */
> > +                                     type = "critical";
> > +                             };
> > +                     };
> > +
> > +                     cooling-maps {
> > +                             map {
> > +                                     trip = <&ddr_critical>;
> > +                                     cooling-device = <&mali THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;

Same here. The cooling-map makes more sense against a passive trip type.

> > +                             };
> > +                     };
> > +             };
> > +     };
> > +
> >       mono_dac: audio-codec-0 {
> >               compatible = "maxim,max98357a";
> >               #sound-dai-cells = <0>;
> > @@ -321,6 +383,7 @@
> >       operating-points-v2 = <&cpu_opp_table>;
> >       clocks = <&clkc CLKID_CPU_CLK>;
> >       clock-latency = <50000>;
> > +     #cooling-cells = <2>;
> >  };
> >
> >  &cpu1 {
> > @@ -328,6 +391,7 @@
> >       operating-points-v2 = <&cpu_opp_table>;
> >       clocks = <&clkc CLKID_CPU_CLK>;
> >       clock-latency = <50000>;
> > +     #cooling-cells = <2>;
> >  };
> >
> >  &cpu2 {
> > @@ -335,6 +399,7 @@
> >       operating-points-v2 = <&cpu_opp_table>;
> >       clocks = <&clkc CLKID_CPU_CLK>;
> >       clock-latency = <50000>;
> > +     #cooling-cells = <2>;
> >  };
> >
> >  &cpu3 {
> > @@ -342,6 +407,7 @@
> >       operating-points-v2 = <&cpu_opp_table>;
> >       clocks = <&clkc CLKID_CPU_CLK>;
> >       clock-latency = <50000>;
> > +     #cooling-cells = <2>;
> >  };
> >
> >  &cvbs_vdac_port {
> > @@ -368,6 +434,10 @@
> >       status = "okay";
> >  };
> >
> > +&mali {
> > +     #cooling-cells = <2>;
> > +};
> > +
>
> Is there a reason these #cooling-cells properties belong in the SoC
> .dtsi and not the board .dts.  Seems like you'll have to repeat this in
> every board .dts which doesn't seem necessary.
>
> Same comment for patch 5/6

Agreed. Even the thermal zones belong in the SoC .dtsi. You can always
override the trip-points in a board .dts if required if you have a
board designed in a different form-factor or with active cooling.

/Amit