linux-kernel - Re: [PATCH v2 2/4] arm64: dts: rockchip: enable temperature driven fan control on Rock 5B

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Date: Thu, 1 Feb 2024 23:15:28 +0400
From: Alexey Charkov <alchark@...il.com>
To: Dragan Simic <dsimic@...jaro.org>
Cc: wens@...nel.org, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Heiko Stuebner <heiko@...ech.de>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Viresh Kumar <viresh.kumar@...aro.org>, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] arm64: dts: rockchip: enable temperature driven
 fan control on Rock 5B

On Thu, Feb 1, 2024 at 9:34 PM Dragan Simic <dsimic@...jaro.org> wrote:
>
> Hello Chen-Yu,
>
> On 2024-02-01 15:26, Chen-Yu Tsai wrote:
> > On Wed, Jan 31, 2024 at 2:22 AM Alexey Charkov <alchark@...il.com>
> > wrote:
> >>
> >> This enables thermal monitoring on Radxa Rock 5B and links the PWM
> >> fan as an active cooling device managed automatically by the thermal
> >> subsystem, with a target SoC temperature of 65C and a minimum-spin
> >> interval from 55C to 65C to ensure airflow when the system gets warm
> >>
> >> Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> >> Signed-off-by: Alexey Charkov <alchark@...il.com>
> >> ---
> >>  arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts | 34
> >> ++++++++++++++++++++++++-
> >>  1 file changed, 33 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts
> >> b/arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts
> >> index a0e303c3a1dc..b485edeef876 100644
> >> --- a/arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts
> >> +++ b/arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts
> >> @@ -52,7 +52,7 @@ led_rgb_b {
> >>
> >>         fan: pwm-fan {
> >>                 compatible = "pwm-fan";
> >> -               cooling-levels = <0 95 145 195 255>;
> >> +               cooling-levels = <0 120 150 180 210 240 255>;
> >>                 fan-supply = <&vcc5v0_sys>;
> >>                 pwms = <&pwm1 0 50000 0>;
> >>                 #cooling-cells = <2>;
> >> @@ -173,6 +173,34 @@ &cpu_l3 {
> >>         cpu-supply = <&vdd_cpu_lit_s0>;
> >>  };
> >>
> >> +&package_thermal {
> >> +       polling-delay = <1000>;
> >> +
> >> +       trips {
> >> +               package_fan0: package-fan0 {
> >> +                       temperature = <55000>;
> >> +                       hysteresis = <2000>;
> >> +                       type = "active";
> >> +               };
> >> +               package_fan1: package-fan1 {
> >> +                       temperature = <65000>;
> >> +                       hysteresis = <2000>;
> >> +                       type = "active";
> >> +               };
> >> +       };
> >> +
> >> +       cooling-maps {
> >> +               map0 {
> >> +                       trip = <&package_fan0>;
> >> +                       cooling-device = <&fan THERMAL_NO_LIMIT 1>;
> >> +               };
> >> +               map1 {
> >> +                       trip = <&package_fan1>;
> >> +                       cooling-device = <&fan 1 THERMAL_NO_LIMIT>;
> >> +               };
> >> +       };
> >> +};
> >> +
> >>  &i2c0 {
> >>         pinctrl-names = "default";
> >>         pinctrl-0 = <&i2c0m2_xfer>;
> >> @@ -731,6 +759,10 @@ regulator-state-mem {
> >>         };
> >>  };
> >>
> >> +&tsadc {
> >> +       status = "okay";
> >> +};
> >> +
> >
> > Is there any reason this can't be enabled by default in the .dtsi file?
> > The thermal sensor doesn't depend on anything external, so there should
> > be no reason to push this down to the board level.
>
> Actually, there is a reason.  Different boards can handle the critical
> overheating differently, by letting the CRU or the PMIC handle it.  This
> was also the case for the RK3399.
>
> Please, have a look at the following DT properties, which are consumed
> by drivers/thermal/rockchip_thermal.c:
>    - "rockchip,hw-tshut-mode"
>    - "rockchip,hw-tshut-polarity"
>
> See also page 1,372 of the RK3588 TRM v1.0.
>
> This has also reminded me to check how is the Rock 5B actually wired,
> just to make sure.  We actually need to provide the two DT properties
> listed above, at least to avoid emitting the warnings.

Well the defaults are already provided in rk3588s.dtsi, so there won't
be any warnings (see lines 2222-2223 in Linus' master version), and
according to the vendor kernel those are also what Rock 5B uses.

This made me think however: what if a board doesn't enable TSADC, but
has OPPs in place for higher voltage and frequency states? There won't
be any throttling (as there won't be any thermal monitoring) and there
might not be a critical shutdown at all if it heats up - possibly even
causing hardware damage. In this case it seems that having TSADC
enabled by default would at least trigger passive cooling, hopefully
avoiding the critical shutdown altogether and making those properties
irrelevant in 99% cases.

Best regards,
Alexey