Popular bpi-r3 pwm fans like this one https://www.amazon.com/youyeetoo-Barebone-Fan-BPI-R3-Integrated/dp/B0CCCTY8PS will not work properly. 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 ----------------------------------------------------------------- At the moment we have following cooling levels defined: cooling-levels = <255 96 0>; for cpu-active-low, cpu-active-medium and cpu-active-high modes correspondingly. Thus only cpu-active-high and cpu-active-low are usable. I think this is wrong. This patch fixes cpu-active-medium settings for bpi-r3 board. PS: I know, the patch is not ideal as it can break pwm fan for some users. There are some peoples that use handmade cooling solutions, but: * discussed cooler is the only 'official' pwm cooler for bpi-r3 available on the market. * most peoples will use passive cooling available on the market or the discussed cooler. * the pwm-fan dts section was added before the official cooler appears on the market. Thus it should not be a lot of harm from this fix. 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 folloving example: === example ========= # cpu temterature 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@xxxxxxxxx> --- 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"; }; -- 2.45.2
