Re: [PATCH net-next v2 1/3] dpll: add frequency monitoring to netlink spec

[Ivan Vecera <ivecera@redhat.com>]

Hi Kuba,

On 4/1/26 5:05 AM, Jakub Kicinski wrote:
> On Mon, 30 Mar 2026 12:55:03 +0200 Ivan Vecera wrote:
>> Add DPLL_A_FREQUENCY_MONITOR device attribute to allow control over
>> the frequency monitor feature. The attribute uses the existing
>> dpll_feature_state enum (enable/disable) and is present in both
>> device-get reply and device-set request.
>>
>> Add DPLL_A_PIN_MEASURED_FREQUENCY pin attribute to expose the measured
>> input frequency in Hz. The attribute is present in the pin-get reply.
> 
> 
>> +      -
>> +        name: frequency-monitor
>> +        type: u32
>> +        enum: feature-state
>> +        doc: Receive or request state of frequency monitor feature.
> 
> reads a bit clunkily - how about:
> 
> 	Current or desired state of the frequency monitor feature.
> 
> ?

Agreed, will update.

> 
>> +          If enabled, dpll device shall measure all currently available
>> +          inputs for their actual input frequency.
>>     -
>>       name: pin
>>       enum-name: dpll_a_pin
>> @@ -456,6 +463,13 @@ attribute-sets:
>>             Value is in PPT (parts per trillion, 10^-12).
>>             Note: This attribute provides higher resolution than the standard
>>             fractional-frequency-offset (which is in PPM).
>> +      -
>> +        name: measured-frequency
>> +        type: u64
>> +        doc: |
>> +          The measured frequency of the input pin in Hz.
>> +          This is the actual frequency being received on the pin,
>> +          as measured by the dpll device hardware.
> 
> If we make this a u64 should it be fixed point? Seems dubious that we'd
> ever be able to measure >4Ghz frequencies, much more likely that we'd
> want sub-1 precision ? So let's say this is fixed point 34.30 ?
> 
Good point. I'm going with a decimal divider (1000) instead of 34.30, 
following the same approach as DPLL_PHASE_OFFSET_DIVIDER. The value
is now in millihertz (mHz) with a DPLL_PIN_MEASURED_FREQUENCY_DIVIDER
constant for userspace to extract integer and fractional parts.

Thanks,
Ivan