[PATCH net-next v3 0/2] dpll: add NCO pin type and zl3073x support

[PATCH net-next v3 0/2] dpll: add NCO pin type and zl3073x support

[Ivan Vecera]

Add a new DPLL_PIN_TYPE_INT_NCO pin type for virtual pins representing
the NCO mode of a DPLL and implement support for it in the zl3073x driver.

Patch 1 adds the new pin type to the DPLL netlink spec and UAPI header.

Patch 2 adds a virtual NCO input pin to the zl3073x driver that allows
userspace to switch a DPLL channel into NCO mode. The pin reports
connected/active state when the channel is in NCO mode and handles
the hardware-specific details of mode transitions including automatic
df_offset capture and 1PPS phase preservation.

Changes:
v3:
  - fixed SoB position
v2:
  - See individual patches for detailed changelogs.

Ivan Vecera (2):
  dpll: add DPLL_PIN_TYPE_INT_NCO pin type
  dpll: zl3073x: add NCO virtual input pin

 Documentation/netlink/specs/dpll.yaml |  13 ++
 drivers/dpll/dpll_nl.c                |   2 +-
 drivers/dpll/zl3073x/chan.c           |  68 ++++++-
 drivers/dpll/zl3073x/chan.h           |  25 +++
 drivers/dpll/zl3073x/dpll.c           | 277 ++++++++++++++++++++++----
 drivers/dpll/zl3073x/dpll.h           |   2 +
 drivers/dpll/zl3073x/regs.h           |   7 +
 include/uapi/linux/dpll.h             |   4 +
 8 files changed, 357 insertions(+), 41 deletions(-)

-- 
2.53.0

[PATCH net-next v3 1/2] dpll: add DPLL_PIN_TYPE_INT_NCO pin type

[Ivan Vecera]

Add DPLL_PIN_TYPE_INT_NCO pin type for virtual pins representing
the NCO mode of a DPLL. 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.

Update the fractional-frequency-offset and fractional-frequency-
offset-ppt attribute documentation to note that for INT_NCO pins
these attributes represent the DPLL's current output frequency
offset from its nominal frequency.

Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
Changes:
v3:
  - Fixed Signed-off-by position
v2:
  - Clarify int-nco pin type documentation to describe frequency
    control via the PTP clock interface instead of generic "controlled
    by the host".
  - Tighten FFO attribute documentation for INT_NCO pins to describe
    the DPLL's output frequency offset from nominal frequency.
  - Mention both fractional-frequency-offset (PPM) and
    fractional-frequency-offset-ppt attributes in the commit message.
---
 Documentation/netlink/specs/dpll.yaml | 13 +++++++++++++
 drivers/dpll/dpll_nl.c                |  2 +-
 include/uapi/linux/dpll.h             |  4 ++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/Documentation/netlink/specs/dpll.yaml b/Documentation/netlink/specs/dpll.yaml
index 91a172617b3a9..5cdb93e8649a0 100644
--- a/Documentation/netlink/specs/dpll.yaml
+++ b/Documentation/netlink/specs/dpll.yaml
@@ -162,6 +162,13 @@ definitions:
       -
         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.
     render-max: true
   -
     type: enum
@@ -453,6 +460,9 @@ attribute-sets:
           offset on the media associated with the pin. Inside
           the pin-parent-device nest it represents the frequency
           offset between the pin and its parent DPLL device.
+          For pins of type PIN_TYPE_INT_NCO this represents
+          the DPLL's current output frequency offset from its
+          nominal frequency.
           Value is in PPM (parts per million).
           This is a lower-precision version of
           fractional-frequency-offset-ppt.
@@ -499,6 +509,9 @@ attribute-sets:
           offset on the media associated with the pin. Inside
           the pin-parent-device nest it represents the frequency
           offset between the pin and its parent DPLL device.
+          For pins of type PIN_TYPE_INT_NCO this represents
+          the DPLL's current output frequency offset from its
+          nominal frequency.
           Value is in PPT (parts per trillion, 10^-12).
           This is a higher-precision version of
           fractional-frequency-offset.
diff --git a/drivers/dpll/dpll_nl.c b/drivers/dpll/dpll_nl.c
index b1d9182c7802f..2dab99202764f 100644
--- a/drivers/dpll/dpll_nl.c
+++ b/drivers/dpll/dpll_nl.c
@@ -61,7 +61,7 @@ static const struct nla_policy dpll_pin_id_get_nl_policy[DPLL_A_PIN_TYPE + 1] =
 	[DPLL_A_PIN_BOARD_LABEL] = { .type = NLA_NUL_STRING, },
 	[DPLL_A_PIN_PANEL_LABEL] = { .type = NLA_NUL_STRING, },
 	[DPLL_A_PIN_PACKAGE_LABEL] = { .type = NLA_NUL_STRING, },
-	[DPLL_A_PIN_TYPE] = NLA_POLICY_RANGE(NLA_U32, 1, 5),
+	[DPLL_A_PIN_TYPE] = NLA_POLICY_RANGE(NLA_U32, 1, 6),
 };
 
 /* DPLL_CMD_PIN_GET - do */
diff --git a/include/uapi/linux/dpll.h b/include/uapi/linux/dpll.h
index cb363cccf2e2a..9245827de3cfd 100644
--- a/include/uapi/linux/dpll.h
+++ b/include/uapi/linux/dpll.h
@@ -127,6 +127,9 @@ enum dpll_type {
  * @DPLL_PIN_TYPE_SYNCE_ETH_PORT: ethernet port PHY's recovered clock
  * @DPLL_PIN_TYPE_INT_OSCILLATOR: device internal oscillator
  * @DPLL_PIN_TYPE_GNSS: GNSS recovered clock
+ * @DPLL_PIN_TYPE_INT_NCO: 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.
  */
 enum dpll_pin_type {
 	DPLL_PIN_TYPE_MUX = 1,
@@ -134,6 +137,7 @@ enum dpll_pin_type {
 	DPLL_PIN_TYPE_SYNCE_ETH_PORT,
 	DPLL_PIN_TYPE_INT_OSCILLATOR,
 	DPLL_PIN_TYPE_GNSS,
+	DPLL_PIN_TYPE_INT_NCO,
 
 	/* private: */
 	__DPLL_PIN_TYPE_MAX,
-- 
2.53.0

[PATCH net-next v3 2/2] dpll: zl3073x: add NCO virtual input pin

[Ivan Vecera]

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

On NCO entry the df_offset captured by nco_auto_read is read from
the register. The nco_auto_read populates df_offset before the mode
switch completes so no delay is needed. The value is static for the
duration of NCO mode and serves as the FFO snapshot reported to
userspace.

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

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>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
Changes:
v3:
  - Fixed Signed-off-by position
v2:
  - Configure nco_auto_read, tod_step_reset and tie_clear once at
    NCO pin registration since these are persistent R/W bits.
    In v1 nco_auto_read was set at registration, while tod_step_reset
    and tie_clear were set on each NCO exit path.
  - Add zl3073x_chan_nco_mode_set() helper that writes mode_refsel
    directly and reads df_offset from the register without the
    DF_READ semaphore protocol. No delay is needed - nco_auto_read
    populates df_offset before the mode switch completes (confirmed
    by HW testing). In v1 the full DF_READ semaphore protocol with
    zl3073x_chan_state_update() was used.
  - Zero df_offset on read failure instead of keeping stale value.
  - Serialize zl3073x_chan_state_update() and
    zl3073x_chan_nco_mode_set() with multiop_lock to prevent
    concurrent df_offset access from the periodic worker.
  - Gate df_offset read in zl3073x_chan_state_update() on LOCK state
    instead of skipping NCO channels in chan_states_update(). This
    keeps mon_status and refsel_status fresh in all modes.
  - Send __dpll_pin_change_ntf() for the NCO pin when leaving NCO
    mode via mode_set() or input pin connect, since the periodic
    worker skips the NCO pin.
  - Add comments explaining the inverted sign convention of the
    dpll_df_offset register.
  - Document why NCO disconnect selects freerun over holdover, the
    shared NCO pin design, and the input pin registration change.
---
 drivers/dpll/zl3073x/chan.c |  68 ++++++++-
 drivers/dpll/zl3073x/chan.h |  25 ++++
 drivers/dpll/zl3073x/dpll.c | 277 +++++++++++++++++++++++++++++++-----
 drivers/dpll/zl3073x/dpll.h |   2 +
 drivers/dpll/zl3073x/regs.h |   7 +
 5 files changed, 339 insertions(+), 40 deletions(-)

diff --git a/drivers/dpll/zl3073x/chan.c b/drivers/dpll/zl3073x/chan.c
index 2fe3c3da84bb5..f5d6c7917e57a 100644
--- a/drivers/dpll/zl3073x/chan.c
+++ b/drivers/dpll/zl3073x/chan.c
@@ -21,6 +21,11 @@ int zl3073x_chan_state_update(struct zl3073x_dev *zldev, u8 index)
 	u64 val;
 	int rc;
 
+	/* Serialize with zl3073x_chan_nco_mode_set() which also
+	 * modifies chan->mode_refsel and chan->df_offset.
+	 */
+	guard(mutex)(&zldev->multiop_lock);
+
 	rc = zl3073x_read_u8(zldev, ZL_REG_DPLL_MON_STATUS(index),
 			     &chan->mon_status);
 	if (rc)
@@ -31,7 +36,10 @@ int zl3073x_chan_state_update(struct zl3073x_dev *zldev, u8 index)
 	if (rc)
 		return rc;
 
-	/* Read df_offset vs tracked reference */
+	/* Read df_offset only when locked to a reference */
+	if (zl3073x_chan_lock_state_get(chan) != ZL_DPLL_MON_STATUS_STATE_LOCK)
+		return 0;
+
 	rc = zl3073x_poll_zero_u8(zldev, ZL_REG_DPLL_DF_READ(index),
 				  ZL_DPLL_DF_READ_SEM);
 	if (rc)
@@ -56,6 +64,50 @@ int zl3073x_chan_state_update(struct zl3073x_dev *zldev, u8 index)
 	return 0;
 }
 
+/**
+ * zl3073x_chan_nco_mode_set - switch DPLL channel to NCO mode
+ * @zldev: pointer to zl3073x_dev structure
+ * @index: DPLL channel index
+ *
+ * Switches the channel to NCO mode, waits for the hardware to
+ * auto-capture the tracking offset via nco_auto_read, then reads
+ * the captured df_offset directly from the register.
+ *
+ * Return: 0 on success, <0 on error
+ */
+int zl3073x_chan_nco_mode_set(struct zl3073x_dev *zldev, u8 index)
+{
+	struct zl3073x_chan *chan = &zldev->chan[index];
+	u8 mode_refsel;
+	u64 val;
+	int rc;
+
+	/* Serialize with zl3073x_chan_state_update() which also
+	 * reads chan->df_offset from the same register.
+	 */
+	guard(mutex)(&zldev->multiop_lock);
+
+	mode_refsel = chan->mode_refsel;
+	FIELD_MODIFY(ZL_DPLL_MODE_REFSEL_MODE, &mode_refsel,
+		     ZL_DPLL_MODE_REFSEL_MODE_NCO);
+
+	rc = zl3073x_write_u8(zldev, ZL_REG_DPLL_MODE_REFSEL(index),
+			      mode_refsel);
+	if (rc)
+		return rc;
+
+	chan->mode_refsel = mode_refsel;
+
+	/* Best-effort read of df_offset captured by nco_auto_read.
+	 * Mode switch already succeeded, so don't propagate a
+	 * df_offset read failure back to userspace.
+	 */
+	rc = zl3073x_read_u48(zldev, ZL_REG_DPLL_DF_OFFSET(index), &val);
+	chan->df_offset = !rc ? sign_extend64(val, 47) : 0;
+
+	return 0;
+}
+
 /**
  * zl3073x_chan_state_fetch - fetch DPLL channel state from hardware
  * @zldev: pointer to zl3073x_dev structure
@@ -71,6 +123,10 @@ int zl3073x_chan_state_fetch(struct zl3073x_dev *zldev, u8 index)
 	struct zl3073x_chan *chan = &zldev->chan[index];
 	int rc, i;
 
+	rc = zl3073x_read_u8(zldev, ZL_REG_DPLL_CTRL(index), &chan->ctrl);
+	if (rc)
+		return rc;
+
 	rc = zl3073x_read_u8(zldev, ZL_REG_DPLL_MODE_REFSEL(index),
 			     &chan->mode_refsel);
 	if (rc)
@@ -145,7 +201,15 @@ int zl3073x_chan_state_set(struct zl3073x_dev *zldev, u8 index,
 	if (!memcmp(&dchan->cfg, &chan->cfg, sizeof(chan->cfg)))
 		return 0;
 
-	/* Direct register write for mode_refsel */
+	/* Direct register writes for ctrl and mode_refsel */
+	if (dchan->ctrl != chan->ctrl) {
+		rc = zl3073x_write_u8(zldev, ZL_REG_DPLL_CTRL(index),
+				      chan->ctrl);
+		if (rc)
+			return rc;
+		dchan->ctrl = chan->ctrl;
+	}
+
 	if (dchan->mode_refsel != chan->mode_refsel) {
 		rc = zl3073x_write_u8(zldev, ZL_REG_DPLL_MODE_REFSEL(index),
 				      chan->mode_refsel);
diff --git a/drivers/dpll/zl3073x/chan.h b/drivers/dpll/zl3073x/chan.h
index 4353809c69122..b9412d223f793 100644
--- a/drivers/dpll/zl3073x/chan.h
+++ b/drivers/dpll/zl3073x/chan.h
@@ -13,6 +13,7 @@ struct zl3073x_dev;
 
 /**
  * struct zl3073x_chan - DPLL channel state
+ * @ctrl: DPLL control register value
  * @mode_refsel: mode and reference selection register value
  * @ref_prio: reference priority registers (4 bits per ref, P/N packed)
  * @mon_status: monitor status register value
@@ -21,6 +22,7 @@ struct zl3073x_dev;
  */
 struct zl3073x_chan {
 	struct_group(cfg,
+		u8	ctrl;
 		u8	mode_refsel;
 		u8	ref_prio[ZL3073X_NUM_REFS / 2];
 	);
@@ -38,6 +40,7 @@ int zl3073x_chan_state_set(struct zl3073x_dev *zldev, u8 index,
 			   const struct zl3073x_chan *chan);
 
 int zl3073x_chan_state_update(struct zl3073x_dev *zldev, u8 index);
+int zl3073x_chan_nco_mode_set(struct zl3073x_dev *zldev, u8 index);
 
 /**
  * zl3073x_chan_df_offset_get - get cached df_offset vs tracked reference
@@ -152,6 +155,28 @@ static inline u8 zl3073x_chan_lock_state_get(const struct zl3073x_chan *chan)
 	return FIELD_GET(ZL_DPLL_MON_STATUS_STATE, chan->mon_status);
 }
 
+/**
+ * zl3073x_chan_mode_is_auto - check if channel is in automatic mode
+ * @chan: pointer to channel state
+ *
+ * Return: true if channel is in automatic mode, false otherwise
+ */
+static inline bool zl3073x_chan_mode_is_auto(const struct zl3073x_chan *chan)
+{
+	return zl3073x_chan_mode_get(chan) == ZL_DPLL_MODE_REFSEL_MODE_AUTO;
+}
+
+/**
+ * zl3073x_chan_mode_is_nco - check if channel is in NCO mode
+ * @chan: pointer to channel state
+ *
+ * Return: true if channel is in NCO mode, false otherwise
+ */
+static inline bool zl3073x_chan_mode_is_nco(const struct zl3073x_chan *chan)
+{
+	return zl3073x_chan_mode_get(chan) == ZL_DPLL_MODE_REFSEL_MODE_NCO;
+}
+
 /**
  * zl3073x_chan_is_ho_ready - check if holdover is ready
  * @chan: pointer to channel state
diff --git a/drivers/dpll/zl3073x/dpll.c b/drivers/dpll/zl3073x/dpll.c
index cff85cdb9d0e5..2d5867dc2bbbc 100644
--- a/drivers/dpll/zl3073x/dpll.c
+++ b/drivers/dpll/zl3073x/dpll.c
@@ -81,6 +81,18 @@ zl3073x_dpll_is_input_pin(struct zl3073x_dpll_pin *pin)
 	return pin->dir == DPLL_PIN_DIRECTION_INPUT;
 }
 
+/**
+ * zl3073x_dpll_is_nco_pin - check if the pin is a virtual NCO pin
+ * @pin: pin to check
+ *
+ * Return: true if pin is a virtual NCO pin, false otherwise.
+ */
+static bool
+zl3073x_dpll_is_nco_pin(struct zl3073x_dpll_pin *pin)
+{
+	return pin->id == ZL3073X_NCO_PIN_ID;
+}
+
 /**
  * zl3073x_dpll_is_p_pin - check if the pin is P-pin
  * @pin: pin to check
@@ -120,6 +132,19 @@ zl3073x_dpll_pin_get_by_ref(struct zl3073x_dpll *zldpll, u8 ref_id)
 	return NULL;
 }
 
+static struct zl3073x_dpll_pin *
+zl3073x_dpll_nco_pin_get(struct zl3073x_dpll *zldpll)
+{
+	struct zl3073x_dpll_pin *pin;
+
+	list_for_each_entry(pin, &zldpll->pins, list) {
+		if (zl3073x_dpll_is_nco_pin(pin))
+			return pin;
+	}
+
+	return NULL;
+}
+
 static int
 zl3073x_dpll_input_pin_esync_get(const struct dpll_pin *dpll_pin,
 				 void *pin_priv,
@@ -605,6 +630,7 @@ zl3073x_dpll_input_pin_state_on_dpll_set(const struct dpll_pin *dpll_pin,
 {
 	struct zl3073x_dpll *zldpll = dpll_priv;
 	struct zl3073x_dpll_pin *pin = pin_priv;
+	struct zl3073x_dpll_pin *nco_pin = NULL;
 	struct zl3073x_chan chan;
 	u8 mode, ref;
 	int rc;
@@ -634,6 +660,10 @@ zl3073x_dpll_input_pin_state_on_dpll_set(const struct dpll_pin *dpll_pin,
 			goto invalid_state;
 		}
 		break;
+	case ZL_DPLL_MODE_REFSEL_MODE_NCO:
+		if (state == DPLL_PIN_STATE_CONNECTED)
+			nco_pin = zl3073x_dpll_nco_pin_get(zldpll);
+		fallthrough;
 	case ZL_DPLL_MODE_REFSEL_MODE_FREERUN:
 	case ZL_DPLL_MODE_REFSEL_MODE_HOLDOVER:
 		if (state == DPLL_PIN_STATE_CONNECTED) {
@@ -676,6 +706,12 @@ zl3073x_dpll_input_pin_state_on_dpll_set(const struct dpll_pin *dpll_pin,
 	if (rc)
 		return rc;
 
+	/* If leaving NCO mode, notify userspace about the NCO pin
+	 * state change - the periodic worker skips the NCO pin.
+	 */
+	if (nco_pin)
+		__dpll_pin_change_ntf(nco_pin->dpll_pin);
+
 	return 0;
 invalid_state:
 	NL_SET_ERR_MSG_MOD(extack, "Invalid pin state for this device mode");
@@ -989,6 +1025,114 @@ zl3073x_dpll_output_pin_state_on_dpll_get(const struct dpll_pin *dpll_pin,
 	return 0;
 }
 
+static int
+zl3073x_dpll_nco_pin_operstate_on_dpll_get(const struct dpll_pin *dpll_pin,
+					   void *pin_priv,
+					   const struct dpll_device *dpll,
+					   void *dpll_priv,
+					   enum dpll_pin_operstate *operstate,
+					   struct netlink_ext_ack *extack)
+{
+	struct zl3073x_dpll *zldpll = dpll_priv;
+	const struct zl3073x_chan *chan;
+
+	chan = zl3073x_chan_state_get(zldpll->dev, zldpll->id);
+	if (zl3073x_chan_mode_is_nco(chan))
+		*operstate = DPLL_PIN_OPERSTATE_ACTIVE;
+	else
+		*operstate = DPLL_PIN_OPERSTATE_STANDBY;
+
+	return 0;
+}
+
+static int
+zl3073x_dpll_nco_pin_state_on_dpll_get(const struct dpll_pin *dpll_pin,
+				       void *pin_priv,
+				       const struct dpll_device *dpll,
+				       void *dpll_priv,
+				       enum dpll_pin_state *state,
+				       struct netlink_ext_ack *extack)
+{
+	struct zl3073x_dpll *zldpll = dpll_priv;
+	const struct zl3073x_chan *chan;
+
+	chan = zl3073x_chan_state_get(zldpll->dev, zldpll->id);
+	if (zl3073x_chan_mode_is_nco(chan))
+		*state = DPLL_PIN_STATE_CONNECTED;
+	else
+		*state = DPLL_PIN_STATE_DISCONNECTED;
+
+	return 0;
+}
+
+static int
+zl3073x_dpll_nco_pin_state_on_dpll_set(const struct dpll_pin *dpll_pin,
+				       void *pin_priv,
+				       const struct dpll_device *dpll,
+				       void *dpll_priv,
+				       enum dpll_pin_state state,
+				       struct netlink_ext_ack *extack)
+{
+	struct zl3073x_dpll *zldpll = dpll_priv;
+	struct zl3073x_chan chan;
+	int rc;
+
+	chan = *zl3073x_chan_state_get(zldpll->dev, zldpll->id);
+
+	switch (state) {
+	case DPLL_PIN_STATE_CONNECTED:
+		/* Already in NCO mode, nothing to do */
+		if (zl3073x_chan_mode_is_nco(&chan))
+			return 0;
+		/* NCO is only allowed in manual mode */
+		if (zl3073x_chan_mode_is_auto(&chan)) {
+			NL_SET_ERR_MSG(extack,
+				       "NCO pin cannot be connected in automatic mode");
+			return -EINVAL;
+		}
+		rc = zl3073x_chan_nco_mode_set(zldpll->dev, zldpll->id);
+		break;
+	case DPLL_PIN_STATE_DISCONNECTED:
+		/* Not in NCO mode, nothing to do */
+		if (!zl3073x_chan_mode_is_nco(&chan))
+			return 0;
+		/* Switch to freerun - holdover averaging was not
+		 * updated during NCO mode.
+		 */
+		zl3073x_chan_mode_set(&chan,
+				      ZL_DPLL_MODE_REFSEL_MODE_FREERUN);
+		rc = zl3073x_chan_state_set(zldpll->dev, zldpll->id, &chan);
+		break;
+	default:
+		NL_SET_ERR_MSG(extack, "invalid pin state for NCO pin");
+		return -EINVAL;
+	}
+
+	return rc;
+}
+
+static int
+zl3073x_dpll_nco_pin_ffo_get(const struct dpll_pin *dpll_pin, void *pin_priv,
+			     const struct dpll_device *dpll, void *dpll_priv,
+			     struct dpll_ffo_param *ffo,
+			     struct netlink_ext_ack *extack)
+{
+	struct zl3073x_dpll *zldpll = dpll_priv;
+	const struct zl3073x_chan *chan;
+
+	chan = zl3073x_chan_state_get(zldpll->dev, zldpll->id);
+	if (!zl3073x_chan_mode_is_nco(chan))
+		return -ENODATA;
+
+	/* NCO register has inverted sign: f_offset = -df_offset / 2^48
+	 * Convert to PPT: ppt = -df * 5^12 / 2^36
+	 */
+	ffo->ffo = -mul_s64_u64_shr(zl3073x_chan_df_offset_get(chan),
+				    244140625, 36);
+
+	return 0;
+}
+
 static int
 zl3073x_dpll_temp_get(const struct dpll_device *dpll, void *dpll_priv,
 		      s32 *temp, struct netlink_ext_ack *extack)
@@ -1057,19 +1201,7 @@ zl3073x_dpll_supported_modes_get(const struct dpll_device *dpll,
 				 void *dpll_priv, unsigned long *modes,
 				 struct netlink_ext_ack *extack)
 {
-	struct zl3073x_dpll *zldpll = dpll_priv;
-	const struct zl3073x_chan *chan;
-
-	chan = zl3073x_chan_state_get(zldpll->dev, zldpll->id);
-
-	/* We support switching between automatic and manual mode, except in
-	 * a case where the DPLL channel is configured to run in NCO mode.
-	 * In this case, report only the manual mode to which the NCO is mapped
-	 * as the only supported one.
-	 */
-	if (zl3073x_chan_mode_get(chan) != ZL_DPLL_MODE_REFSEL_MODE_NCO)
-		__set_bit(DPLL_MODE_AUTOMATIC, modes);
-
+	__set_bit(DPLL_MODE_AUTOMATIC, modes);
 	__set_bit(DPLL_MODE_MANUAL, modes);
 
 	return 0;
@@ -1163,6 +1295,7 @@ zl3073x_dpll_mode_set(const struct dpll_device *dpll, void *dpll_priv,
 		      enum dpll_mode mode, struct netlink_ext_ack *extack)
 {
 	struct zl3073x_dpll *zldpll = dpll_priv;
+	struct zl3073x_dpll_pin *nco_pin = NULL;
 	struct zl3073x_chan chan;
 	u8 hw_mode, ref;
 	int rc;
@@ -1186,6 +1319,9 @@ zl3073x_dpll_mode_set(const struct dpll_device *dpll, void *dpll_priv,
 		else
 			hw_mode = ZL_DPLL_MODE_REFSEL_MODE_HOLDOVER;
 	} else {
+		if (zl3073x_chan_mode_is_nco(&chan))
+			nco_pin = zl3073x_dpll_nco_pin_get(zldpll);
+
 		/* We are switching from manual to automatic mode:
 		 * - if there is a valid reference selected then ensure that
 		 *   it is selectable after switch to automatic mode
@@ -1217,6 +1353,12 @@ zl3073x_dpll_mode_set(const struct dpll_device *dpll, void *dpll_priv,
 		return rc;
 	}
 
+	/* If leaving NCO mode, notify userspace about the NCO pin
+	 * state change - the periodic worker skips the NCO pin.
+	 */
+	if (nco_pin)
+		__dpll_pin_change_ntf(nco_pin->dpll_pin);
+
 	return 0;
 }
 
@@ -1310,6 +1452,15 @@ static const struct dpll_pin_ops zl3073x_dpll_output_pin_ops = {
 	.state_on_dpll_get = zl3073x_dpll_output_pin_state_on_dpll_get,
 };
 
+static const struct dpll_pin_ops zl3073x_dpll_nco_pin_ops = {
+	.supported_ffo = BIT(DPLL_FFO_PIN_DEVICE),
+	.direction_get = zl3073x_dpll_pin_direction_get,
+	.ffo_get = zl3073x_dpll_nco_pin_ffo_get,
+	.operstate_on_dpll_get = zl3073x_dpll_nco_pin_operstate_on_dpll_get,
+	.state_on_dpll_get = zl3073x_dpll_nco_pin_state_on_dpll_get,
+	.state_on_dpll_set = zl3073x_dpll_nco_pin_state_on_dpll_set,
+};
+
 static const struct dpll_device_ops zl3073x_dpll_device_ops = {
 	.lock_status_get = zl3073x_dpll_lock_status_get,
 	.mode_get = zl3073x_dpll_mode_get,
@@ -1457,7 +1608,9 @@ zl3073x_dpll_pin_unregister(struct zl3073x_dpll_pin *pin)
 
 	WARN(!pin->dpll_pin, "DPLL pin is not registered\n");
 
-	if (zl3073x_dpll_is_input_pin(pin))
+	if (zl3073x_dpll_is_nco_pin(pin))
+		ops = &zl3073x_dpll_nco_pin_ops;
+	else if (zl3073x_dpll_is_input_pin(pin))
 		ops = &zl3073x_dpll_input_pin_ops;
 	else
 		ops = &zl3073x_dpll_output_pin_ops;
@@ -1510,20 +1663,13 @@ zl3073x_dpll_pin_is_registrable(struct zl3073x_dpll *zldpll,
 				enum dpll_pin_direction dir, u8 index)
 {
 	struct zl3073x_dev *zldev = zldpll->dev;
-	const struct zl3073x_chan *chan;
 	bool is_diff, is_enabled;
 	const char *name;
 
-	chan = zl3073x_chan_state_get(zldev, zldpll->id);
-
 	if (dir == DPLL_PIN_DIRECTION_INPUT) {
 		u8 ref_id = zl3073x_input_pin_ref_get(index);
 		const struct zl3073x_ref *ref;
 
-		/* Skip the pin if the DPLL is running in NCO mode */
-		if (zl3073x_chan_mode_get(chan) == ZL_DPLL_MODE_REFSEL_MODE_NCO)
-			return false;
-
 		name = "REF";
 		ref = zl3073x_ref_state_get(zldev, ref_id);
 		is_diff = zl3073x_ref_is_diff(ref);
@@ -1564,6 +1710,64 @@ zl3073x_dpll_pin_is_registrable(struct zl3073x_dpll *zldpll,
 	return true;
 }
 
+static const struct dpll_pin_properties zl3073x_dpll_nco_pin_props = {
+	.type = DPLL_PIN_TYPE_INT_NCO,
+	.package_label = "NCO",
+	.capabilities = DPLL_PIN_CAPABILITIES_STATE_CAN_CHANGE,
+};
+
+static int
+zl3073x_dpll_nco_pin_register(struct zl3073x_dpll *zldpll)
+{
+	struct zl3073x_dpll_pin *pin;
+	struct zl3073x_chan chan;
+	int rc;
+
+	/* Configure ctrl bits for NCO operation:
+	 * - nco_auto_read: auto-capture tracking offset on NCO entry
+	 * - tod_step_reset: apply negated ToD step on NCO exit
+	 * - tie_clear: PPS DPLLs re-align outputs on NCO exit
+	 */
+	chan = *zl3073x_chan_state_get(zldpll->dev, zldpll->id);
+	FIELD_MODIFY(ZL_DPLL_CTRL_NCO_AUTO_READ, &chan.ctrl, 1);
+	FIELD_MODIFY(ZL_DPLL_CTRL_TOD_STEP_RST, &chan.ctrl, 1);
+	FIELD_MODIFY(ZL_DPLL_CTRL_TIE_CLEAR, &chan.ctrl,
+		     zldpll->type == DPLL_TYPE_PPS ? 1 : 0);
+	rc = zl3073x_chan_state_set(zldpll->dev, zldpll->id, &chan);
+	if (rc)
+		return rc;
+
+	pin = zl3073x_dpll_pin_alloc(zldpll, DPLL_PIN_DIRECTION_INPUT,
+				     ZL3073X_NCO_PIN_ID);
+	if (IS_ERR(pin))
+		return PTR_ERR(pin);
+
+	pin->dpll_pin = dpll_pin_get(zldpll->dev->clock_id, ZL3073X_NCO_PIN_ID,
+				     THIS_MODULE, &zl3073x_dpll_nco_pin_props,
+				     &pin->tracker);
+	if (IS_ERR(pin->dpll_pin)) {
+		rc = PTR_ERR(pin->dpll_pin);
+		goto err_pin_get;
+	}
+
+	rc = dpll_pin_register(zldpll->dpll_dev, pin->dpll_pin,
+			       &zl3073x_dpll_nco_pin_ops, pin);
+	if (rc)
+		goto err_register;
+
+	list_add(&pin->list, &zldpll->pins);
+
+	return 0;
+
+err_register:
+	dpll_pin_put(pin->dpll_pin, &pin->tracker);
+err_pin_get:
+	pin->dpll_pin = NULL;
+	kfree(pin);
+
+	return rc;
+}
+
 /**
  * zl3073x_dpll_pins_register - register all registerable DPLL pins
  * @zldpll: pointer to zl3073x_dpll structure
@@ -1609,6 +1813,11 @@ zl3073x_dpll_pins_register(struct zl3073x_dpll *zldpll)
 		list_add(&pin->list, &zldpll->pins);
 	}
 
+	/* Register NCO virtual input pin */
+	rc = zl3073x_dpll_nco_pin_register(zldpll);
+	if (rc)
+		goto error;
+
 	return 0;
 
 error:
@@ -1644,8 +1853,8 @@ zl3073x_dpll_device_register(struct zl3073x_dpll *zldpll)
 		return rc;
 	}
 
-	rc = dpll_device_register(zldpll->dpll_dev,
-				  zl3073x_prop_dpll_type_get(zldev, zldpll->id),
+	zldpll->type = zl3073x_prop_dpll_type_get(zldev, zldpll->id);
+	rc = dpll_device_register(zldpll->dpll_dev, zldpll->type,
 				  &zldpll->ops, zldpll);
 	if (rc) {
 		dpll_device_put(zldpll->dpll_dev, &zldpll->tracker);
@@ -1752,6 +1961,10 @@ zl3073x_dpll_pin_ffo_check(struct zl3073x_dpll_pin *pin)
 		return false;
 
 	chan = zl3073x_chan_state_get(zldpll->dev, zldpll->id);
+	/* df_offset register has inverted sign, but we report FFO as
+	 * pin-vs-DPLL (not DPLL-vs-reference), so the two inversions
+	 * cancel out: ppt = df * 5^12 / 2^36
+	 */
 	ffo = mul_s64_u64_shr(zl3073x_chan_df_offset_get(chan),
 			      244140625, 36);
 
@@ -1815,10 +2028,8 @@ zl3073x_dpll_changes_check(struct zl3073x_dpll *zldpll)
 	struct zl3073x_dev *zldev = zldpll->dev;
 	enum dpll_lock_status lock_status;
 	struct device *dev = zldev->dev;
-	const struct zl3073x_chan *chan;
 	struct zl3073x_dpll_pin *pin;
 	int rc;
-	u8 mode;
 
 	zldpll->check_count++;
 
@@ -1837,15 +2048,6 @@ zl3073x_dpll_changes_check(struct zl3073x_dpll *zldpll)
 		dpll_device_change_ntf(zldpll->dpll_dev);
 	}
 
-	/* Input pin monitoring does make sense only in automatic
-	 * or forced reference modes.
-	 */
-	chan = zl3073x_chan_state_get(zldev, zldpll->id);
-	mode = zl3073x_chan_mode_get(chan);
-	if (mode != ZL_DPLL_MODE_REFSEL_MODE_AUTO &&
-	    mode != ZL_DPLL_MODE_REFSEL_MODE_REFLOCK)
-		return;
-
 	/* Update phase offset latch registers for this DPLL if the phase
 	 * offset monitor feature is enabled.
 	 */
@@ -1863,10 +2065,9 @@ zl3073x_dpll_changes_check(struct zl3073x_dpll *zldpll)
 		enum dpll_pin_operstate operstate;
 		bool pin_changed = false;
 
-		/* Output pins change checks are not necessary because output
-		 * states are constant.
-		 */
-		if (!zl3073x_dpll_is_input_pin(pin))
+		/* Only physical input pins need monitoring */
+		if (!zl3073x_dpll_is_input_pin(pin) ||
+		    zl3073x_dpll_is_nco_pin(pin))
 			continue;
 
 		rc = zl3073x_dpll_ref_operstate_get(pin, &operstate);
diff --git a/drivers/dpll/zl3073x/dpll.h b/drivers/dpll/zl3073x/dpll.h
index 434c32a7db123..0920e4d31ab35 100644
--- a/drivers/dpll/zl3073x/dpll.h
+++ b/drivers/dpll/zl3073x/dpll.h
@@ -19,6 +19,7 @@
  * @ops: DPLL device operations for this instance
  * @dpll_dev: pointer to registered DPLL device
  * @tracker: tracking object for the acquired reference
+ * @type: DPLL type (PPS or EEC)
  * @lock_status: last saved DPLL lock status
  * @pins: list of pins
  * @change_work: device change notification work
@@ -33,6 +34,7 @@ struct zl3073x_dpll {
 	struct dpll_device_ops		ops;
 	struct dpll_device		*dpll_dev;
 	dpll_tracker			tracker;
+	enum dpll_type			type;
 	enum dpll_lock_status		lock_status;
 	struct list_head		pins;
 	struct work_struct		change_work;
diff --git a/drivers/dpll/zl3073x/regs.h b/drivers/dpll/zl3073x/regs.h
index 9578f00095282..8f1dd3a2ac214 100644
--- a/drivers/dpll/zl3073x/regs.h
+++ b/drivers/dpll/zl3073x/regs.h
@@ -17,6 +17,7 @@
 #define ZL3073X_NUM_OUTPUT_PINS	(ZL3073X_NUM_OUTS * 2)
 #define ZL3073X_NUM_PINS	(ZL3073X_NUM_INPUT_PINS + \
 				 ZL3073X_NUM_OUTPUT_PINS)
+#define ZL3073X_NCO_PIN_ID	ZL3073X_NUM_PINS
 
 /*
  * Register address structure:
@@ -164,6 +165,12 @@
 #define ZL_DPLL_MODE_REFSEL_MODE_NCO		4
 #define ZL_DPLL_MODE_REFSEL_REF			GENMASK(7, 4)
 
+#define ZL_REG_DPLL_CTRL(_idx)						\
+	ZL_REG_IDX(_idx, 5, 0x05, 1, ZL3073X_MAX_CHANNELS, 4)
+#define ZL_DPLL_CTRL_TIE_CLEAR			BIT(0)
+#define ZL_DPLL_CTRL_TOD_STEP_RST		BIT(2)
+#define ZL_DPLL_CTRL_NCO_AUTO_READ		BIT(7)
+
 #define ZL_REG_DPLL_DF_READ(_idx)					\
 	ZL_REG_IDX(_idx, 5, 0x28, 1, ZL3073X_MAX_CHANNELS, 1)
 #define ZL_DPLL_DF_READ_SEM			BIT(4)
-- 
2.53.0

Re: [PATCH net-next v3 2/2] dpll: zl3073x: add NCO virtual input pin

[Jakub Kicinski]

This is an AI-generated review of your patch. The human sending this
email says "I think the report / question about the SEM wasn't asked
on v2?"
---
dpll: zl3073x: add NCO virtual input pin

This change adds a virtual NCO input pin that lets userspace switch a
DPLL channel into NCO mode, and registers it with the new
DPLL_PIN_TYPE_INT_NCO type. It also rearranges chan->df_offset
handling so it is only read when the DPLL is locked, and adds a
ZL_REG_DPLL_CTRL register cache plus state_set support.

> diff --git a/drivers/dpll/zl3073x/chan.c b/drivers/dpll/zl3073x/chan.c
> index 2fe3c3da84bb..f5d6c7917e57 100644
> --- a/drivers/dpll/zl3073x/chan.c
> +++ b/drivers/dpll/zl3073x/chan.c
> @@ -21,6 +21,11 @@ int zl3073x_chan_state_update(struct zl3073x_dev *zldev, u8 index)
>  	u64 val;
>  	int rc;
>  
> +	/* Serialize with zl3073x_chan_nco_mode_set() which also
> +	 * modifies chan->mode_refsel and chan->df_offset.
> +	 */
> +	guard(mutex)(&zldev->multiop_lock);
> +
>  	rc = zl3073x_read_u8(zldev, ZL_REG_DPLL_MON_STATUS(index),
>  			     &chan->mon_status);
>  	if (rc)
> @@ -31,7 +36,10 @@ int zl3073x_chan_state_update(struct zl3073x_dev *zldev, u8 index)
>  	if (rc)
>  		return rc;
>  
> -	/* Read df_offset vs tracked reference */
> +	/* Read df_offset only when locked to a reference */
> +	if (zl3073x_chan_lock_state_get(chan) != ZL_DPLL_MON_STATUS_STATE_LOCK)
> +		return 0;
> +

[Medium]
With this early return, when the DPLL boots in NCO mode and
zl3073x_chan_state_fetch() calls zl3073x_chan_state_update(),
chan->df_offset is left at the kzalloc-zeroed 0 (NCO mode is not
ZL_DPLL_MON_STATUS_STATE_LOCK).

zl3073x_dpll_nco_pin_register() then calls zl3073x_chan_state_set() to
update the ctrl bits, but state_set() never reads
ZL_REG_DPLL_DF_OFFSET. The only place that populates df_offset in NCO
mode is zl3073x_chan_nco_mode_set(), which only runs on a userspace
CONNECTED transition for the NCO pin.

Does this leave zl3073x_dpll_nco_pin_ffo_get() reporting ffo=0 forever
on a system that boots already in NCO mode, until userspace explicitly
disconnects and reconnects the NCO pin?

The commit message says:

    The value is static for the duration of NCO mode and serves as the
    FFO snapshot reported to userspace.

Does that statement still hold for the boot-in-NCO-mode case?

>  	rc = zl3073x_poll_zero_u8(zldev, ZL_REG_DPLL_DF_READ(index),
>  				  ZL_DPLL_DF_READ_SEM);
>  	if (rc)
> @@ -56,6 +64,50 @@ int zl3073x_chan_state_update(struct zl3073x_dev *zldev, u8 index)
>  	return 0;
>  }
>  
> +/**
> + * zl3073x_chan_nco_mode_set - switch DPLL channel to NCO mode
> + * @zldev: pointer to zl3073x_dev structure
> + * @index: DPLL channel index
> + *
> + * Switches the channel to NCO mode, waits for the hardware to
> + * auto-capture the tracking offset via nco_auto_read, then reads
> + * the captured df_offset directly from the register.
> + *
> + * Return: 0 on success, <0 on error
> + */
> +int zl3073x_chan_nco_mode_set(struct zl3073x_dev *zldev, u8 index)
> +{
> +	struct zl3073x_chan *chan = &zldev->chan[index];
> +	u8 mode_refsel;
> +	u64 val;
> +	int rc;
> +
> +	/* Serialize with zl3073x_chan_state_update() which also
> +	 * reads chan->df_offset from the same register.
> +	 */
> +	guard(mutex)(&zldev->multiop_lock);
> +
> +	mode_refsel = chan->mode_refsel;
> +	FIELD_MODIFY(ZL_DPLL_MODE_REFSEL_MODE, &mode_refsel,
> +		     ZL_DPLL_MODE_REFSEL_MODE_NCO);
> +
> +	rc = zl3073x_write_u8(zldev, ZL_REG_DPLL_MODE_REFSEL(index),
> +			      mode_refsel);
> +	if (rc)
> +		return rc;
> +
> +	chan->mode_refsel = mode_refsel;
> +
> +	/* Best-effort read of df_offset captured by nco_auto_read.
> +	 * Mode switch already succeeded, so don't propagate a
> +	 * df_offset read failure back to userspace.
> +	 */
> +	rc = zl3073x_read_u48(zldev, ZL_REG_DPLL_DF_OFFSET(index), &val);
> +	chan->df_offset = !rc ? sign_extend64(val, 47) : 0;
> +
> +	return 0;
> +}

[Medium]
Should this read use the same DF_READ semaphore handshake that
zl3073x_chan_state_update() uses for the same DF_OFFSET register?

The existing path does:

    poll ZL_DPLL_DF_READ_SEM == 0
    write ZL_DPLL_DF_READ_SEM | ZL_DPLL_DF_READ_REF_OFST
    poll ZL_DPLL_DF_READ_SEM == 0
    read ZL_REG_DPLL_DF_OFFSET

The new path writes MODE_REFSEL=NCO and then immediately reads the
48-bit DF_OFFSET register without any handshake.

The commit message says:

    The nco_auto_read populates df_offset before the mode switch
    completes so no delay is needed.

Is there a datasheet reference for this guarantee that could be cited
in the code comment?

If the auto-capture takes any non-zero amount of time after the
MODE_REFSEL bus write completes, can this read return stale REFLOCK-era
data or a torn value across the multi-byte 48-bit register? Combined
with the early return added to zl3073x_chan_state_update() for non-LOCK
states, would such a value persist for the entire NCO session?

[Medium]
There is also a question about reader synchronization for chan->df_offset.

zl3073x_chan_nco_mode_set() writes chan->df_offset under
zldev->multiop_lock. The periodic worker zl3073x_dpll_changes_check()
calls zl3073x_dpll_pin_ffo_check(), which reads chan->df_offset via
zl3073x_chan_df_offset_get() without holding multiop_lock:

static inline s64
zl3073x_chan_df_offset_get(const struct zl3073x_chan *chan)
{
    return chan->df_offset;
}

Consider: DPLL is in REFLOCK with a pin locked, the worker has finished
zl3073x_chan_state_update() (released multiop_lock), is iterating pins,
and enters ffo_check just as a netlink connect of the NCO pin calls
zl3073x_chan_nco_mode_set() and overwrites chan->df_offset.

drivers/dpll/zl3073x/Kconfig has no 64BIT dependency, so on 32-bit
builds the s64 store is two 32-bit stores. Can the worker observe a
torn value, push it through atomic64_xchg into pin->freq_offset, and
emit a dpll_pin_change_ntf with that value?

Pre-patch, df_offset was only written from state_update() in the worker
context, so writer and reader were sequential. Should the ffo_check
reader take multiop_lock, or chan->df_offset be promoted to an
atomic64_t/READ_ONCE pair?

> +
>  /**
>   * zl3073x_chan_state_fetch - fetch DPLL channel state from hardware
>   * @zldev: pointer to zl3073x_dev structure

[ ... ]