Hi Krzysztof, On 9/05/24 19:06, Krzysztof Kozlowski wrote: > On 08/05/2024 23:55, Chris Packham wrote: >> Add documentation for the pwm-initial-duty-cycle and >> pwm-initial-frequency properties. These allow the starting state of the >> PWM outputs to be set to cater for hardware designs where undesirable >> amounts of noise is created by the default hardware state. >> >> Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx> >> --- >> >> Notes: >> Changes in v2: >> - Document 0 as a valid value (leaves hardware as-is) >> >> .../devicetree/bindings/hwmon/adt7475.yaml | 27 ++++++++++++++++++- >> 1 file changed, 26 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/devicetree/bindings/hwmon/adt7475.yaml b/Documentation/devicetree/bindings/hwmon/adt7475.yaml >> index 051c976ab711..97deda082b4a 100644 >> --- a/Documentation/devicetree/bindings/hwmon/adt7475.yaml >> +++ b/Documentation/devicetree/bindings/hwmon/adt7475.yaml >> @@ -51,6 +51,30 @@ properties: >> enum: [0, 1] >> default: 1 >> >> + adi,pwm-initial-duty-cycle: >> + description: | >> + Configures the initial duty cycle for the PWM outputs. The hardware >> + default is 100% but this may cause unwanted fan noise at startup. Set >> + this to a value from 0 (0% duty cycle) to 255 (100% duty cycle). >> + $ref: /schemas/types.yaml#/definitions/uint32-array >> + minItems: 3 >> + maxItems: 3 >> + items: >> + minimum: 0 >> + maximum: 255 >> + default: 255 >> + >> + adi,pwm-initial-frequency: > Frequency usually has some units, so use appropriate unit suffix and > drop $ref. Maybe that's just target-rpm property? > > But isn't this duplicating previous property? This is fan controller, > not PWM provider (in any case you miss proper $refs to pwm.yaml or > fan-common.yaml), so the only thing you initially want to configure is > the fan rotation, not specific PWM waveform. If you you want to > configure specific PWM waveform, then it's a PWM provider... but it is > not... Confused. There's two things going on here. There's a PWM duty cycle which is configurable from 0% to 100%. It might be nice if this was expressed as a percentage instead of 0-255 but I went with the latter because that's how the sysfs ABI for the duty cycle works. The frequency (which I'll call adi,pwm-initial-frequency-hz in v3) affects how that duty cycle is presented to the fans. So you could still have a duty cycle of 50% at any frequency. What frequency is best depends on the kind of fans being used. In my particular case the lower frequencies end up with the fans oscillating annoyingly so I use the highest setting. > > Best regards, > Krzysztof >
