Re: [PATCH v2] arm64: dts: amlogic: meson-sm1-odroid-hc4: add the fan tachometer

[Neil Armstrong <neil.armstrong@linaro.org>]

On 10/6/26 18:36, Igor Velkov via B4 Relay wrote:
> From: Igor Velkov <iav@iav.lv>
> 
> The fan connector routes the fan's tachometer output to GPIOX_7, but
> the fan node does not describe it. pwm-fan therefore registers no
> fan1_input, and the fan speed cannot be read.
> 
> Describe the line as the fan's interrupt, and mux the pin as a GPIO
> input without bias: R109 on the board pulls the line up to VDDAO_3V3
> (schematic rev1.0, sheet 31).
> 
> Tested on ODROID-HC4: fan1_input reads 0 with the fan stopped and
> rises with the duty cycle, to about 4200 rpm at full speed.
> 
> Assisted-by: LLM
> Signed-off-by: Igor Velkov <iav@iav.lv>
> ---
> Changes in v2:
> - Mux GPIOX_7 as a GPIO input without bias (Neil).
> - Link to v1: https://lore.kernel.org/r/20261006-hc4-fan-tach-v1-1-4e7cecf0b45b@iav.lv
> ---
>   arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts b/arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts
> index 5f15c2299509..64602aff1d81 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts
> +++ b/arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts
> @@ -21,6 +21,10 @@ fan0: pwm-fan {
>   		#cooling-cells = <2>;
>   		cooling-levels = <0 120 170 220>;
>   		pwms = <&pwm_cd 1 40000 0>;
> +		interrupt-parent = <&gpio_intc>;
> +		interrupts = <IRQID_GPIOX_7 IRQ_TYPE_EDGE_FALLING>;
> +		pinctrl-0 = <&fan_tach_pins>;
> +		pinctrl-names = "default";
>   	};
>   
>   	leds {
> @@ -114,6 +118,17 @@ &pcie {
>   	reset-gpios = <&gpio GPIOH_4 GPIO_ACTIVE_LOW>;
>   };
>   
> +&periphs_pinctrl {
> +	fan_tach_pins: fan-tach {
> +		mux {
> +			groups = "GPIOX_7";
> +			function = "gpio_periphs";
> +			bias-disable;
> +			output-disable;
> +		};
> +	};
> +};
> +
>   &pwm_cd {
>   	status = "okay";
>   	pinctrl-names = "default";
> 
> ---
> base-commit: b44e2be772f866985cafdf90355285069ea68495
> change-id: 20261006-hc4-fan-tach-440c1b874a04
> 
> Best regards,

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>

Thanks,
Neil

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