Subject: [PATCH net-next v3 1/3] dpll: add frequency monitoring to netlink spec

From: Ivan Vecera <[email-masked]>
Date: Wed, 1 Apr 2026 11:12:35 +0200

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 millihertz (mHz). The attribute is present in the
pin-get reply. Add DPLL_PIN_MEASURED_FREQUENCY_DIVIDER constant to
allow userspace to extract integer and fractional parts.

Reviewed-by: Vadim Fedorenko <[email-masked]>
Signed-off-by: Ivan Vecera <[email-masked]>
---
Changes v2 -> v3:
- Improved frequency-monitor doc wording (Jakub)
- Changed measured-frequency to mHz with divider constant (Jakub)

Changes v1 -> v2:
- Renamed actual-frequency to measured-frequency (Vadim)
---
 Documentation/driver-api/dpll.rst     | 20 +++++++++++++++
 Documentation/netlink/specs/dpll.yaml | 35 +++++++++++++++++++++++++++
 drivers/dpll/dpll_nl.c                |  5 ++--
 include/uapi/linux/dpll.h             |  5 +++-
 4 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/Documentation/driver-api/dpll.rst b/Documentation/driver-api/dpll.rst
index 83118c728ed90..93c191b2d0898 100644
--- a/Documentation/driver-api/dpll.rst
+++ b/Documentation/driver-api/dpll.rst
@@ -250,6 +250,24 @@ in the ``DPLL_A_PIN_PHASE_OFFSET`` attribute.
   ``DPLL_A_PHASE_OFFSET_MONITOR`` attr state of a feature
   =============================== ========================
 
+Frequency monitor
+=================
+
+Some DPLL devices may offer the capability to measure the actual
+frequency of all available input pins. The attribute and current feature state
+shall be included in the response message of the ``DPLL_CMD_DEVICE_GET``
+command for supported DPLL devices. In such cases, users can also control
+the feature using the ``DPLL_CMD_DEVICE_SET`` command by setting the
+``enum dpll_feature_state`` values for the attribute.
+Once enabled the measured input frequency for each input pin shall be
+returned in the ``DPLL_A_PIN_MEASURED_FREQUENCY`` attribute. The value
+is in millihertz (mHz), using ``DPLL_PIN_MEASURED_FREQUENCY_DIVIDER``
+as the divider.
+
+  =============================== ========================
+  ``DPLL_A_FREQUENCY_MONITOR``    attr state of a feature
+  =============================== ========================
+
 Embedded SYNC
 =============
 
@@ -411,6 +429,8 @@ according to attribute purpose.
       ``DPLL_A_PIN_STATE``             attr state of pin on the parent
                                        pin
     ``DPLL_A_PIN_CAPABILITIES``        attr bitmask of pin capabilities
+    ``DPLL_A_PIN_MEASURED_FREQUENCY``  attr measured frequency of
+                                       an input pin in mHz
   ==================================== ==================================
 
   ==================================== =================================
diff --git a/Documentation/netlink/specs/dpll.yaml b/Documentation/netlink/specs/dpll.yaml
index 3dd48a32f7837..40465a3d7fc20 100644
--- a/Documentation/netlink/specs/dpll.yaml
+++ b/Documentation/netlink/specs/dpll.yaml
@@ -240,6 +240,20 @@ definitions:
       integer part of a measured phase offset value.
       Value of (DPLL_A_PHASE_OFFSET % DPLL_PHASE_OFFSET_DIVIDER) is a
       fractional part of a measured phase offset value.
+  -
+    type: const
+    name: pin-measured-frequency-divider
+    value: 1000
+    doc: |
+      pin measured frequency divider allows userspace to calculate
+      a value of measured input frequency as a fractional value with
+      three digit decimal precision (millihertz).
+      Value of (DPLL_A_PIN_MEASURED_FREQUENCY /
+      DPLL_PIN_MEASURED_FREQUENCY_DIVIDER) is an integer part of
+      a measured frequency value.
+      Value of (DPLL_A_PIN_MEASURED_FREQUENCY %
+      DPLL_PIN_MEASURED_FREQUENCY_DIVIDER) is a fractional part of
+      a measured frequency value.
   -
     type: enum
     name: feature-state
@@ -319,6 +333,13 @@ attribute-sets:
         name: phase-offset-avg-factor
         type: u32
         doc: Averaging factor applied to calculation of reported phase offset.
+      -
+        name: frequency-monitor
+        type: u32
+        enum: feature-state
+        doc: Current or desired state of the frequency monitor feature.
+          If enabled, dpll device shall measure all currently available
+          inputs for their actual input frequency.
   -
     name: pin
     enum-name: dpll_a_pin
@@ -456,6 +477,17 @@ 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 millihertz (mHz).
+          Value of (DPLL_A_PIN_MEASURED_FREQUENCY /
+          DPLL_PIN_MEASURED_FREQUENCY_DIVIDER) is an integer part (Hz)
+          of a measured frequency value.
+          Value of (DPLL_A_PIN_MEASURED_FREQUENCY %
+          DPLL_PIN_MEASURED_FREQUENCY_DIVIDER) is a fractional part
+          of a measured frequency value.
 
   -
     name: pin-parent-device
@@ -544,6 +576,7 @@ operations:
             - type
             - phase-offset-monitor
             - phase-offset-avg-factor
+            - frequency-monitor
 
       dump:
         reply: *dev-attrs
@@ -563,6 +596,7 @@ operations:
             - mode
             - phase-offset-monitor
             - phase-offset-avg-factor
+            - frequency-monitor
     -
       name: device-create-ntf
       doc: Notification about device appearing
@@ -643,6 +677,7 @@ operations:
             - esync-frequency-supported
             - esync-pulse
             - reference-sync
+            - measured-frequency
 
       dump:
         request:
diff --git a/drivers/dpll/dpll_nl.c b/drivers/dpll/dpll_nl.c
index a2b22d4921142..1e652340a5d73 100644
--- a/drivers/dpll/dpll_nl.c
+++ b/drivers/dpll/dpll_nl.c
@@ -43,11 +43,12 @@ static const struct nla_policy dpll_device_get_nl_policy[DPLL_A_ID + 1] = {
 };
 
 /* DPLL_CMD_DEVICE_SET - do */
-static const struct nla_policy dpll_device_set_nl_policy[DPLL_A_PHASE_OFFSET_AVG_FACTOR + 1] = {
+static const struct nla_policy dpll_device_set_nl_policy[DPLL_A_FREQUENCY_MONITOR + 1] = {
 	[DPLL_A_ID] = { .type = NLA_U32, },
 	[DPLL_A_MODE] = NLA_POLICY_RANGE(NLA_U32, 1, 2),
 	[DPLL_A_PHASE_OFFSET_MONITOR] = NLA_POLICY_MAX(NLA_U32, 1),
 	[DPLL_A_PHASE_OFFSET_AVG_FACTOR] = { .type = NLA_U32, },
+	[DPLL_A_FREQUENCY_MONITOR] = NLA_POLICY_MAX(NLA_U32, 1),
 };
 
 /* DPLL_CMD_PIN_ID_GET - do */
@@ -115,7 +116,7 @@ static const struct genl_split_ops dpll_nl_ops[] = {
 		.doit		= dpll_nl_device_set_doit,
 		.post_doit	= dpll_post_doit,
 		.policy		= dpll_device_set_nl_policy,
-		.maxattr	= DPLL_A_PHASE_OFFSET_AVG_FACTOR,
+		.maxattr	= DPLL_A_FREQUENCY_MONITOR,
 		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
 	},
 	{
diff --git a/include/uapi/linux/dpll.h b/include/uapi/linux/dpll.h
index de0005f28e5c5..871685f7c353b 100644
--- a/include/uapi/linux/dpll.h
+++ b/include/uapi/linux/dpll.h
@@ -191,7 +191,8 @@ enum dpll_pin_capabilities {
 	DPLL_PIN_CAPABILITIES_STATE_CAN_CHANGE = 4,
 };
 
-#define DPLL_PHASE_OFFSET_DIVIDER	1000
+#define DPLL_PHASE_OFFSET_DIVIDER		1000
+#define DPLL_PIN_MEASURED_FREQUENCY_DIVIDER	1000
 
 /**
  * enum dpll_feature_state - Allow control (enable/disable) and status checking
@@ -218,6 +219,7 @@ enum dpll_a {
 	DPLL_A_CLOCK_QUALITY_LEVEL,
 	DPLL_A_PHASE_OFFSET_MONITOR,
 	DPLL_A_PHASE_OFFSET_AVG_FACTOR,
+	DPLL_A_FREQUENCY_MONITOR,
 
 	__DPLL_A_MAX,
 	DPLL_A_MAX = (__DPLL_A_MAX - 1)
@@ -254,6 +256,7 @@ enum dpll_a_pin {
 	DPLL_A_PIN_REFERENCE_SYNC,
 	DPLL_A_PIN_PHASE_ADJUST_GRAN,
 	DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET_PPT,
+	DPLL_A_PIN_MEASURED_FREQUENCY,
 
 	__DPLL_A_PIN_MAX,
 	DPLL_A_PIN_MAX = (__DPLL_A_PIN_MAX - 1)
-- 
2.52.0