Re: [PATCH net-next v5 1/4] dpll: add DPLL_PIN_TYPE_INT_NCO pin type

[Ivan Vecera]

On 6/9/26 4:00 PM, Kubalewski, Arkadiusz wrote:
> > From: Jiri Pirko <jiri@xxxxxxxxxxx>
> > Sent: Tuesday, June 9, 2026 10:51 AM
> >
> > Mon, Jun 08, 2026 at 07:03:46PM +0200, arkadiusz.kubalewski@xxxxxxxxx
> > wrote:
> > > > From: Ivan Vecera <ivecera@xxxxxxxxxx>
> > > > Sent: Monday, June 8, 2026 5:48 PM
> > > >
> > > > On 6/8/26 4:43 PM, Kubalewski, Arkadiusz wrote:
> > > > > > From: Ivan Vecera <ivecera@xxxxxxxxxx>
> > > > > > Sent: Sunday, May 31, 2026 9:44 PM
> > > > > > ...
> > > > > >         -
> > > > > >           name: gnss
> > > > > >           doc: GNSS recovered clock
> > > > > > +      -
> > > > > > +        name: int-nco
> > > > > > +        doc: |
> > > > > > +          Device internal numerically controlled oscillator.
> > > > > > +          When connected as a DPLL input, the DPLL enters NCO mode
> > > > > > +          where the output frequency is adjusted by the host via
> > > > > > +          the PTP clock interface.
> > > > >
> > > > > Hi Ivan!
> > > > >
> > > > > How would you control this in case of automatic mode dpll?
> > > > > Automatic mode DPLL shall be controlled on HW level, such pin brakes
> > > > > that rule and requires some driver magic to show it is higher
> > > > > priority then the rest of the pins?
> > > >
> > > > The NCO pin can be connected only in manual mode. In other words a DPLL
> > > > in automatic mode cannot select NCO pin (switch to NCO mode) by its own.
> > >
> > > Being picky on DPLL_MODE for enabling feature is not something we can
> > > allow if it is not related to HW limitation, is it?
> > > Could you please elaborate why it is not possible for AUTOMATIC mode?
> >
> > In automatic mode, the pin selection logic is defined upon prio. I can
> > imagine that if NCO pin has the highest prio of the available ones,
> > it gets picked. I would be aligned 100% with automatic mode behaviour.
> > Is there a real usecase for it?
> >
> > [..]
>
> This is not true. AUTOMATIC mode is HW solution, SW driver ONLY
> configures priorities on the inputs, not manages the active inputs.
> This brakes that behavior, the SW driver would have to manually
> override the AUTMATIC mode to be fed from such NCO pin as it doesn't
> exists on it's priority list, HW cannot pick or use it.

Correct, AUTO mode is hardware feature and it should not be emulated
by a driver. If the hardware does not support it then the switching
between input references should be done by userspace (by monitoring
ffo, phase_offset, operstate).

> The real use case is that any DPLL can switch the mode to this one
> instead of implementing MANUAL mode just to use the feature with a
> 'virtual' pin.

I don't expect this... but it is up to a driver. I don't plan such
functionality in zl3073x as the NCO pin does not expose prio_get() and
prio_set() callbacks - so it is clear that this pin cannot be part of
the automatic selection.

Ivan