dpll: zl3073x: add PTP clock support

Add PTP clock support for the ZL3073x DPLL driver. A PTP clock device
is registered for each DPLL channel regardless of the initial channel
state, providing gettimex64, settime64, adjtime, adjfine, adjphase
and getmaxphase callbacks.

Callback availability depends on the current channel state:
- adjfine: when NCO pin is connected (returns -EOPNOTSUPP otherwise)
- adjphase: available when tracking a reference, uses TIE write
- adjtime: always available and uses
  * phase step for sub-second deltas when NCO pin is connected
  * TIE write when tracking a reference
  * plain ToD read-modify-write otherwise
- gettime/settime: always available

The adjtime callback splits multi-second adjustments into a ToD
read-modify-write for the seconds part and a sub-second mechanism
(phase step or TIE write) for the remainder. On partial failure
where seconds were already committed, success is returned to
prevent the PTP servo from retrying and applying seconds again.

All PTP callbacks are serialized by the existing per-DPLL zldpll->lock
mutex, which is also used by DPLL pin and device callbacks.

Reviewed-by: Petr Oros <poros@redhat.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Tested-by: Chris du Quesnay <Chris.duQuesnay@microchip.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Link: https://patch.msgid.link/20260814082656.306534-4-ivecera@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions