Re: [PATCH v3] arm64: dts: mediatek: mt7986-bpi-r3: Change fan PWM value for mid speed

[Frank Wunderlich]

Am 26. Mai 2025 14:31:23 MESZ schrieb Mikhail Kshevetskiy <mikhail.kshevetskiy at iopsys.eu>:
>Popular cheap PWM fans for this machine, like the ones coming in
>heatsink+fan combos will not work properly at the currently defined
>medium speed. Trying different pwm setting using a command
>
>  echo $value > /sys/devices/platform/pwm-fan/hwmon/hwmon1/pwm1
>
>I found:
>
>  pwm1 value     fan rotation speed   cpu temperature     notes
>  -----------------------------------------------------------------
>    0            maximal              31.5 Celsius        too noisy
>   40            optimal              35.2 Celsius        no noise hearable
>   95            minimal
>   above 95      does not rotate      55.5 Celsius
>  -----------------------------------------------------------------
>
>Thus only cpu-active-high and cpu-active-low modes are usable.
>I think this is wrong.
>
>This patch fixes cpu-active-medium settings for bpi-r3 board.
>
>I know, the patch is not ideal as it can break pwm fan for some users.
>Likely this is the only official mt7986-bpi-r3 heatsink+fan solution
>available on the market.
>
>This patch may not be enough. Users may wants to tweak their thermal_zone0
>trip points, thus tuning fan rotation speed depending on cpu temperature.
>That can be done on the base of the following example:
>
>  === example =========
>  # cpu temperature below 25 Celsius degrees, no rotation
>  echo 25000 > /sys/class/thermal/thermal_zone0/trip_point_4_temp
>  # cpu temperature in [25..32] Celsius degrees, normal rotation speed
>  echo 32000 > /sys/class/thermal/thermal_zone0/trip_point_3_temp
>  # cpu temperature above 50 Celsius degrees, max rotation speed
>  echo 50000 > /sys/class/thermal/thermal_zone0/trip_point_2_temp
>  =====================
>
>Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy at iopsys.eu>
>
>---
>From Frank Wunderlich <frank-w at public-files.de>
>Date: 04.03.2025
>>
>> sorry for delay
>>
>> i have the fan from sinovoip and that was working for me, but if your fan only works with new values, i have no point against this change.
>
>Frank, does it means that you are signed off this patch?

Let it count as

Acked-by: Frank Wunderlich <frank-w at public-files.de>

Because i cannot test these values,as i only have 1 pwm fan for r3 in my main router :p
Maybe R4 fan works too,but not yet tested.

Not sure if the complete testcase has to be in the commit description,but this is maintainers decision.

>Changes from v1 to v2:
> * improve patch description
>
>Changes from v2 to v3:
> * added question to Frank Wunderlich
>---
> arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts b/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
>index ed79ad1ae871..b0cc0cbdff0f 100644
>--- a/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
>+++ b/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
>@@ -42,7 +42,7 @@ fan: pwm-fan {
> 		compatible = "pwm-fan";
> 		#cooling-cells = <2>;
> 		/* cooling level (0, 1, 2) - pwm inverted */
>-		cooling-levels = <255 96 0>;
>+		cooling-levels = <255 40 0>;
> 		pwms = <&pwm 0 10000>;
> 		status = "okay";
> 	};


regards Frank