[PATCH 0/3] Initial thermal management for Lichee Pi 4A board

[PATCH 0/3] Initial thermal management for Lichee Pi 4A board

[Icenowy Zheng]

The SoM+Dock design of Lichee Pi 4A is quite bad at dissipating heat, so
active cooling is quite important for it.

This patchset tries to do some initial active cooling for it, by
utilizing software PWM to drive the fan.

Ths 1st patch adds PVT temperature coefficients, as seen in the SoC
manual and BSP 6.6 kernel device trees.

The 2nd patch adds thermal zone information for the 2 thermal sensors in
the PVT block.

The 3rd patch adds soft PWM + PWM fan, and makes the fan an active
cooling device of the CPU thermal zone. 

Icenowy Zheng (3):
  riscv: dts: thead: th1520: add coefficients to the PVT node
  riscv: dts: thead: th1520: add initial thermal zones
  riscv: dts: thead: th1520: add soft PWM fan for Lichee Pi 4A

 .../boot/dts/thead/th1520-lichee-pi-4a.dts    | 53 +++++++++++++++++++
 arch/riscv/boot/dts/thead/th1520.dtsi         | 29 ++++++++++
 2 files changed, 82 insertions(+)

-- 
2.50.1


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[PATCH 1/3] riscv: dts: thead: th1520: add coefficients to the PVT node

[Icenowy Zheng]

The manual of TH1520 contains a set of coefficients a little different
to the driver default ones.

Add them to the device tree node of PVT.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
---
 arch/riscv/boot/dts/thead/th1520.dtsi | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
index 03f1d73190499..e9c81bdabed8a 100644
--- a/arch/riscv/boot/dts/thead/th1520.dtsi
+++ b/arch/riscv/boot/dts/thead/th1520.dtsi
@@ -676,6 +676,10 @@ pvt: pvt@fffff4e000 {
 			reg-names = "common", "ts", "pd", "vm";
 			clocks = <&aonsys_clk>;
 			#thermal-sensor-cells = <1>;
+			moortec,ts-coeff-g = <42740>;
+			moortec,ts-coeff-h = <220500>;
+			moortec,ts-coeff-j = <(-160)>;
+			moortec,ts-coeff-cal5 = <4094>;
 		};
 
 		gpio@fffff52000 {
-- 
2.50.1


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Re: [PATCH 1/3] riscv: dts: thead: th1520: add coefficients to the PVT node

[Drew Fustini]

On Sat, Aug 16, 2025 at 05:32:07PM +0800, Icenowy Zheng wrote:
> The manual of TH1520 contains a set of coefficients a little different
> to the driver default ones.
> 
> Add them to the device tree node of PVT.
> 
> Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
> ---
>  arch/riscv/boot/dts/thead/th1520.dtsi | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
> index 03f1d73190499..e9c81bdabed8a 100644
> --- a/arch/riscv/boot/dts/thead/th1520.dtsi
> +++ b/arch/riscv/boot/dts/thead/th1520.dtsi
> @@ -676,6 +676,10 @@ pvt: pvt@fffff4e000 {
>  			reg-names = "common", "ts", "pd", "vm";
>  			clocks = <&aonsys_clk>;
>  			#thermal-sensor-cells = <1>;
> +			moortec,ts-coeff-g = <42740>;
> +			moortec,ts-coeff-h = <220500>;
> +			moortec,ts-coeff-j = <(-160)>;
> +			moortec,ts-coeff-cal5 = <4094>;
>  		};
>  
>  		gpio@fffff52000 {
> -- 
> 2.50.1
> 

I think moortec,ts-coeff-XXX will need to be rounded to nearest multiple
of 100 as dtbs_check warns that:

pvt@fffff4e000: moortec,ts-coeff-g: 42740 is not a multiple of 100
	from schema $id: http://devicetree.org/schemas/hwmon/moortec,mr75203.yaml#
pvt@fffff4e000: moortec,ts-coeff-j: -160 is not a multiple of 100
	from schema $id: http://devicetree.org/schemas/hwmon/moortec,mr75203.yaml#
pvt@fffff4e000: moortec,ts-coeff-g: 42740 is not a multiple of 100
	from schema $id: http://devicetree.org/schemas/hwmon/moortec,mr75203.yaml#
pvt@fffff4e000: moortec,ts-coeff-j: -160 is not a multiple of 100
	from schema $id: http://devicetree.org/schemas/hwmon/moortec,mr75203.yaml#

Thanks,
Drew

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Re: [PATCH 1/3] riscv: dts: thead: th1520: add coefficients to the PVT node

[Icenowy Zheng]

在 2025-08-22星期五的 14:29 -0700，Drew Fustini写道：
> On Sat, Aug 16, 2025 at 05:32:07PM +0800, Icenowy Zheng wrote:
> > The manual of TH1520 contains a set of coefficients a little
> > different
> > to the driver default ones.
> > 
> > Add them to the device tree node of PVT.
> > 
> > Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
> > ---
> >  arch/riscv/boot/dts/thead/th1520.dtsi | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi
> > b/arch/riscv/boot/dts/thead/th1520.dtsi
> > index 03f1d73190499..e9c81bdabed8a 100644
> > --- a/arch/riscv/boot/dts/thead/th1520.dtsi
> > +++ b/arch/riscv/boot/dts/thead/th1520.dtsi
> > @@ -676,6 +676,10 @@ pvt: pvt@fffff4e000 {
> >                         reg-names = "common", "ts", "pd", "vm";
> >                         clocks = <&aonsys_clk>;
> >                         #thermal-sensor-cells = <1>;
> > +                       moortec,ts-coeff-g = <42740>;
> > +                       moortec,ts-coeff-h = <220500>;
> > +                       moortec,ts-coeff-j = <(-160)>;
> > +                       moortec,ts-coeff-cal5 = <4094>;
> >                 };
> >  
> >                 gpio@fffff52000 {
> > -- 
> > 2.50.1
> > 
> 
> I think moortec,ts-coeff-XXX will need to be rounded to nearest
> multiple
> of 100 as dtbs_check warns that:
> 
> pvt@fffff4e000: moortec,ts-coeff-g: 42740 is not a multiple of 100
>         from schema $id:
> http://devicetree.org/schemas/hwmon/moortec,mr75203.yaml#
> pvt@fffff4e000: moortec,ts-coeff-j: -160 is not a multiple of 100
>         from schema $id:
> http://devicetree.org/schemas/hwmon/moortec,mr75203.yaml#
> pvt@fffff4e000: moortec,ts-coeff-g: 42740 is not a multiple of 100
>         from schema $id:
> http://devicetree.org/schemas/hwmon/moortec,mr75203.yaml#
> pvt@fffff4e000: moortec,ts-coeff-j: -160 is not a multiple of 100
>         from schema $id:
> http://devicetree.org/schemas/hwmon/moortec,mr75203.yaml#

Then it looks like the binding is to be blamed for not allowing fine
tweak.

> 
> Thanks,
> Drew

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[PATCH 2/3] riscv: dts: thead: th1520: add initial thermal zones

[Icenowy Zheng]

As the PVT sensors's "T" means thermal, add thermal zones for the
thermal sensors.

Because of the current lack of DVFS, only a critical trip point is added
now.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
---
 arch/riscv/boot/dts/thead/th1520.dtsi | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
index e9c81bdabed8a..a48eca5def606 100644
--- a/arch/riscv/boot/dts/thead/th1520.dtsi
+++ b/arch/riscv/boot/dts/thead/th1520.dtsi
@@ -701,4 +701,29 @@ gpio4: gpio-controller@0 {
 			};
 		};
 	};
+
+	thermal-zones {
+		cpu-thermal {
+			polling-delay-passive = <250>;
+			polling-delay = <15000>;
+
+			thermal-sensors = <&pvt 0>;
+
+			trips {
+				cpu_crit: crit-trip {
+					/* milliCelsius */
+					temperature = <110000>;
+					hysteresis = <2000>;
+					type = "critical";
+				};
+			};
+		};
+
+		ddrc-thermal {
+			polling-delay-passive = <250>;
+			polling-delay = <15000>;
+
+			thermal-sensors = <&pvt 1>;
+		};
+	};
 };
-- 
2.50.1


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[PATCH 3/3] riscv: dts: thead: th1520: add soft PWM fan for Lichee Pi 4A

[Icenowy Zheng]

Because of the SoM+Dock design of Lichee Pi 4A, heat dissipation does
not work well; fortunately it comes with a fan port with PWM driving
capability.

As the hardware PWM controller of Lichee Pi 4A isn't ready yet, drive it
with pwm-gpio driver (software PWM) now.

A long PWM period is used, because not only software PWM is used, but
also the fan port is a 2-pin one and fast PWM might confuse the BLDC
driver on fans.

Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
---
 .../boot/dts/thead/th1520-lichee-pi-4a.dts    | 53 +++++++++++++++++++
 arch/riscv/boot/dts/thead/th1520.dtsi         |  2 +-
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts b/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
index 4020c727f09e8..f696db01353c5 100644
--- a/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
+++ b/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
@@ -4,6 +4,7 @@
  */
 
 #include "th1520-lichee-module-4a.dtsi"
+#include <dt-bindings/gpio/gpio.h>
 
 / {
 	model = "Sipeed Lichee Pi 4A";
@@ -28,6 +29,58 @@ aliases {
 	chosen {
 		stdout-path = "serial0:115200n8";
 	};
+
+	gpio_pwm: gpio-pwm {
+		#pwm-cells = <3>;
+		compatible = "pwm-gpio";
+		gpios = <&gpio3 3 GPIO_ACTIVE_HIGH>;
+	};
+
+	fan: pwm-fan {
+		compatible = "pwm-fan";
+		#cooling-cells = <2>;
+		pwms = <&gpio_pwm 0 100000000 0>;
+		cooling-levels = <0 66 196 255>;
+	};
+};
+
+&cpu_thermal_zone {
+	trips {
+		fan_trip0: fan-trip-0 {
+			temperature = <40000>;
+			hysteresis = <8000>;
+			type = "active";
+		};
+
+		fan_trip1: fan-trip-1 {
+			temperature = <50000>;
+			hysteresis = <8000>;
+			type = "active";
+		};
+
+		fan_trip2: fan-trip-2 {
+			temperature = <60000>;
+			hysteresis = <8000>;
+			type = "active";
+		};
+	};
+
+	cooling-maps {
+		map-active-0 {
+			cooling-device = <&fan 1 1>;
+			trip = <&fan_trip0>;
+		};
+
+		map-active-1 {
+			cooling-device = <&fan 2 2>;
+			trip = <&fan_trip1>;
+		};
+
+		map-active-2 {
+			cooling-device = <&fan 3 3>;
+			trip = <&fan_trip2>;
+		};
+	};
 };
 
 &padctrl0_apsys {
diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
index a48eca5def606..5ac8044a05f1e 100644
--- a/arch/riscv/boot/dts/thead/th1520.dtsi
+++ b/arch/riscv/boot/dts/thead/th1520.dtsi
@@ -703,7 +703,7 @@ gpio4: gpio-controller@0 {
 	};
 
 	thermal-zones {
-		cpu-thermal {
+		cpu_thermal_zone: cpu-thermal {
 			polling-delay-passive = <250>;
 			polling-delay = <15000>;
 
-- 
2.50.1


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Re: [PATCH 3/3] riscv: dts: thead: th1520: add soft PWM fan for Lichee Pi 4A

[Drew Fustini]

On Sat, Aug 16, 2025 at 05:32:09PM +0800, Icenowy Zheng wrote:
> Because of the SoM+Dock design of Lichee Pi 4A, heat dissipation does
> not work well; fortunately it comes with a fan port with PWM driving
> capability.
> 
> As the hardware PWM controller of Lichee Pi 4A isn't ready yet, drive it
> with pwm-gpio driver (software PWM) now.
> 
> A long PWM period is used, because not only software PWM is used, but
> also the fan port is a 2-pin one and fast PWM might confuse the BLDC
> driver on fans.
> 
> Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
> ---
>  .../boot/dts/thead/th1520-lichee-pi-4a.dts    | 53 +++++++++++++++++++
>  arch/riscv/boot/dts/thead/th1520.dtsi         |  2 +-
>  2 files changed, 54 insertions(+), 1 deletion(-)

Is it possible to reconcile the work that Michal is doing with the
hardware PWM controller series [1] and this series?

The PWM controller does need Rust which works okay for me when using
llvm but that might not be the case for everyone. Maybe there is some
way to use the pwm controller if available and then failback to gpio if
not.

Thanks,
Drew 

[1] https://lore.kernel.org/linux-riscv/20250806-rust-next-pwm-working-fan-for-sending-v13-7-690b669295b6@samsung.com/

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Re: [PATCH 3/3] riscv: dts: thead: th1520: add soft PWM fan for Lichee Pi 4A

[Drew Fustini]

On Sat, Aug 16, 2025 at 05:32:09PM +0800, Icenowy Zheng wrote:
> Because of the SoM+Dock design of Lichee Pi 4A, heat dissipation does
> not work well; fortunately it comes with a fan port with PWM driving
> capability.
> 
> As the hardware PWM controller of Lichee Pi 4A isn't ready yet, drive it
> with pwm-gpio driver (software PWM) now.
> 
> A long PWM period is used, because not only software PWM is used, but
> also the fan port is a 2-pin one and fast PWM might confuse the BLDC
> driver on fans.
> 
> Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
> ---
>  .../boot/dts/thead/th1520-lichee-pi-4a.dts    | 53 +++++++++++++++++++
>  arch/riscv/boot/dts/thead/th1520.dtsi         |  2 +-
>  2 files changed, 54 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts b/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
> index 4020c727f09e8..f696db01353c5 100644
> --- a/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
> +++ b/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
> @@ -4,6 +4,7 @@
>   */
>  
>  #include "th1520-lichee-module-4a.dtsi"
> +#include <dt-bindings/gpio/gpio.h>
>  
>  / {
>  	model = "Sipeed Lichee Pi 4A";
> @@ -28,6 +29,58 @@ aliases {
>  	chosen {
>  		stdout-path = "serial0:115200n8";
>  	};
> +
> +	gpio_pwm: gpio-pwm {
> +		#pwm-cells = <3>;
> +		compatible = "pwm-gpio";
> +		gpios = <&gpio3 3 GPIO_ACTIVE_HIGH>;
> +	};

I think the node name needs to be 'pwm' instead of 'gpio-pwm' as dtbs_check
warns that:

gpio-pwm: $nodename:0: 'gpio-pwm' does not match '^pwm(@.*|-([0-9]|[1-9][0-9]+))?$'
from schema $id: http://devicetree.org/schemas/pwm/pwm-gpio.yaml#

Thanks,
Drew

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Re: [PATCH 3/3] riscv: dts: thead: th1520: add soft PWM fan for Lichee Pi 4A

[Icenowy Zheng]

在 2025-08-22星期五的 14:32 -0700，Drew Fustini写道：
> On Sat, Aug 16, 2025 at 05:32:09PM +0800, Icenowy Zheng wrote:
> > Because of the SoM+Dock design of Lichee Pi 4A, heat dissipation
> > does
> > not work well; fortunately it comes with a fan port with PWM
> > driving
> > capability.
> > 
> > As the hardware PWM controller of Lichee Pi 4A isn't ready yet,
> > drive it
> > with pwm-gpio driver (software PWM) now.
> > 
> > A long PWM period is used, because not only software PWM is used,
> > but
> > also the fan port is a 2-pin one and fast PWM might confuse the
> > BLDC
> > driver on fans.
> > 
> > Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
> > ---
> >  .../boot/dts/thead/th1520-lichee-pi-4a.dts    | 53
> > +++++++++++++++++++
> >  arch/riscv/boot/dts/thead/th1520.dtsi         |  2 +-
> >  2 files changed, 54 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
> > b/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
> > index 4020c727f09e8..f696db01353c5 100644
> > --- a/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
> > +++ b/arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts
> > @@ -4,6 +4,7 @@
> >   */
> >  
> >  #include "th1520-lichee-module-4a.dtsi"
> > +#include <dt-bindings/gpio/gpio.h>
> >  
> >  / {
> >         model = "Sipeed Lichee Pi 4A";
> > @@ -28,6 +29,58 @@ aliases {
> >         chosen {
> >                 stdout-path = "serial0:115200n8";
> >         };
> > +
> > +       gpio_pwm: gpio-pwm {
> > +               #pwm-cells = <3>;
> > +               compatible = "pwm-gpio";
> > +               gpios = <&gpio3 3 GPIO_ACTIVE_HIGH>;
> > +       };
> 
> I think the node name needs to be 'pwm' instead of 'gpio-pwm' as
> dtbs_check
> warns that:

Sounds reasonable, although 'pwm' seems to be too generic.

But the recommended names below looks quite generic too... Is it just
some copy-pasta?

Well, maybe just take 'pwm' or 'pwm-0' now?

> 
> gpio-pwm: $nodename:0: 'gpio-pwm' does not match '^pwm(@.*|-([0-
> 9]|[1-9][0-9]+))?$'
> from schema $id: http://devicetree.org/schemas/pwm/pwm-gpio.yaml#
> 
> Thanks,
> Drew


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Re: [PATCH 0/3] Initial thermal management for Lichee Pi 4A board

[Drew Fustini]

On Sat, Aug 16, 2025 at 05:32:06PM +0800, Icenowy Zheng wrote:
> The SoM+Dock design of Lichee Pi 4A is quite bad at dissipating heat, so
> active cooling is quite important for it.
> 
> This patchset tries to do some initial active cooling for it, by
> utilizing software PWM to drive the fan.
> 
> Ths 1st patch adds PVT temperature coefficients, as seen in the SoC
> manual and BSP 6.6 kernel device trees.
> 
> The 2nd patch adds thermal zone information for the 2 thermal sensors in
> the PVT block.
> 
> The 3rd patch adds soft PWM + PWM fan, and makes the fan an active
> cooling device of the CPU thermal zone. 
> 
> Icenowy Zheng (3):
>   riscv: dts: thead: th1520: add coefficients to the PVT node
>   riscv: dts: thead: th1520: add initial thermal zones
>   riscv: dts: thead: th1520: add soft PWM fan for Lichee Pi 4A
> 
>  .../boot/dts/thead/th1520-lichee-pi-4a.dts    | 53 +++++++++++++++++++
>  arch/riscv/boot/dts/thead/th1520.dtsi         | 29 ++++++++++
>  2 files changed, 82 insertions(+)
> 
> -- 
> 2.50.1
> 

I just tested this on top of:
[PATCH v3 0/4] clk: thead: Changes to TH1520 clock driver for disp
[PATCH v2 0/2] clk: thead: th1520-ap: allow gate cascade and fix padctrl0

The fan is spinning when system boots at expected. That is nice that
GPIO can be used until the PWM controller driver is ready. hwmon0 shows
both temp inputs holding steady at 43.3 C and 44.4 C.

Thanks,
Drew


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