dpll: zl3073x: add NCO virtual input pin

Add a virtual NCO (Numerically Controlled Oscillator) input pin that
lets userspace switch a DPLL channel into NCO mode. A single NCO pin
is shared across all DPLL channels - each channel has its own
independent connection state. The NCO pin is registered with the new
DPLL_PIN_TYPE_INT_NCO type and reports DPLL_PIN_STATE_CONNECTED /
DPLL_PIN_OPERSTATE_ACTIVE when the channel is in NCO mode.

At NCO pin registration the following bits are configured in
dpll_ctrl_x:
  - nco_auto_read: auto-capture tracking offset on NCO entry
  - tod_step_reset: apply negated ToD step accumulator on NCO exit
  - tie_clear: PPS DPLLs set 1 to re-align outputs on NCO exit,
               EEC DPLLs keep 0 to prevent an unwanted TIE write

Before switching to NCO mode, dpll_df_read_x is configured with
ref_ofst=0 and cmd=ACC_I so that nco_auto_read captures the
accumulated I-part offset relative to the master clock. Without
this, the captured df_offset would be near zero (offset relative
to the input reference after lock).

On NCO entry the df_offset captured by nco_auto_read is read from
the register. Per the datasheet, nco_auto_read only captures a valid
offset when entering NCO from reflock, auto or holdover mode; from
freerun the captured value is not meaningful and df_offset is marked as
ZL_DPLL_DF_OFFSET_UNKNOWN. The same sentinel is set in
chan_state_update() when the channel is not locked, and both FFO
consumers (NCO pin and input pin) guard against it.

Disconnecting the NCO pin switches to freerun rather than holdover
because holdover averaging is not updated during NCO mode.

When connecting the NCO pin displaces a previously connected input
pin (reflock mode), a change notification is sent for that input pin.

Input reference pins are now always registered regardless of the
initial DPLL mode. Previously they were skipped when the DPLL was
in NCO mode, but the NCO pin provides the proper mechanism for
mode transitions.

Reviewed-by: Petr Oros <poros@redhat.com>
Tested-by: Chris du Quesnay <Chris.duQuesnay@microchip.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Link: https://patch.msgid.link/20260630125536.720717-6-ivecera@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

0 files changed, 0 insertions, 0 deletions