dpll: add reference-sync netlink attribute

Add new netlink attribute to allow user space configuration of reference
sync pin pairs, where both pins are used to provide one clock signal
consisting of both: base frequency and sync signal.

Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Milena Olech <milena.olech@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Link: https://patch.msgid.link/20250626135219.1769350-2-arkadiusz.kubalewski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/driver-api/dpll.rst

@@ -253,6 +253,31 @@ the pin.
   ``DPLL_A_PIN_ESYNC_PULSE``                pulse type of Embedded SYNC
   ========================================= =================================
 
+Reference SYNC
+==============
+
+The device may support the Reference SYNC feature, which allows the combination
+of two inputs into a input pair. In this configuration, clock signals
+from both inputs are used to synchronize the DPLL device. The higher frequency
+signal is utilized for the loop bandwidth of the DPLL, while the lower frequency
+signal is used to syntonize the output signal of the DPLL device. This feature
+enables the provision of a high-quality loop bandwidth signal from an external
+source.
+
+A capable input provides a list of inputs that can be bound with to create
+Reference SYNC. To control this feature, the user must request a desired
+state for a target pin: use ``DPLL_PIN_STATE_CONNECTED`` to enable or
+``DPLL_PIN_STATE_DISCONNECTED`` to disable the feature. An input pin can be
+bound to only one other pin at any given time.
+
+  ============================== ==========================================
+  ``DPLL_A_PIN_REFERENCE_SYNC``  nested attribute for providing info or
+                                 requesting configuration of the Reference
+                                 SYNC feature
+    ``DPLL_A_PIN_ID``            target pin id for Reference SYNC feature
+    ``DPLL_A_PIN_STATE``         state of Reference SYNC connection
+  ============================== ==========================================
+
 Configuration commands group
 ============================
 

Documentation/netlink/specs/dpll.yaml

@@ -428,6 +428,15 @@ attribute-sets:
         doc: |
           A ratio of high to low state of a SYNC signal pulse embedded
           into base clock frequency. Value is in percents.
+      -
+        name: reference-sync
+        type: nest
+        multi-attr: true
+        nested-attributes: reference-sync
+        doc: |
+          Capable pin provides list of pins that can be bound to create a
+          reference-sync pin pair.
+
   -
     name: pin-parent-device
     subset-of: pin
@@ -458,6 +467,14 @@ attribute-sets:
         name: frequency-min
       -
         name: frequency-max
+  -
+    name: reference-sync
+    subset-of: pin
+    attributes:
+      -
+        name: id
+      -
+        name: state
 
 operations:
   enum-name: dpll_cmd
@@ -598,6 +615,7 @@ operations:
             - esync-frequency
             - esync-frequency-supported
             - esync-pulse
+            - reference-sync
 
       dump:
         request:
@@ -625,6 +643,7 @@ operations:
             - parent-pin
             - phase-adjust
             - esync-frequency
+            - reference-sync
     -
       name: pin-create-ntf
       doc: Notification about pin appearing

drivers/dpll/dpll_nl.c

@@ -24,6 +24,11 @@ const struct nla_policy dpll_pin_parent_pin_nl_policy[DPLL_A_PIN_STATE + 1] = {
 	[DPLL_A_PIN_STATE] = NLA_POLICY_RANGE(NLA_U32, 1, 3),
 };
 
+const struct nla_policy dpll_reference_sync_nl_policy[DPLL_A_PIN_STATE + 1] = {
+	[DPLL_A_PIN_ID] = { .type = NLA_U32, },
+	[DPLL_A_PIN_STATE] = NLA_POLICY_RANGE(NLA_U32, 1, 3),
+};
+
 /* DPLL_CMD_DEVICE_ID_GET - do */
 static const struct nla_policy dpll_device_id_get_nl_policy[DPLL_A_TYPE + 1] = {
 	[DPLL_A_MODULE_NAME] = { .type = NLA_NUL_STRING, },
@@ -63,7 +68,7 @@ static const struct nla_policy dpll_pin_get_dump_nl_policy[DPLL_A_PIN_ID + 1] =
 };
 
 /* DPLL_CMD_PIN_SET - do */
-static const struct nla_policy dpll_pin_set_nl_policy[DPLL_A_PIN_ESYNC_FREQUENCY + 1] = {
+static const struct nla_policy dpll_pin_set_nl_policy[DPLL_A_PIN_REFERENCE_SYNC + 1] = {
 	[DPLL_A_PIN_ID] = { .type = NLA_U32, },
 	[DPLL_A_PIN_FREQUENCY] = { .type = NLA_U64, },
 	[DPLL_A_PIN_DIRECTION] = NLA_POLICY_RANGE(NLA_U32, 1, 2),
@@ -73,6 +78,7 @@ static const struct nla_policy dpll_pin_set_nl_policy[DPLL_A_PIN_ESYNC_FREQUENCY
 	[DPLL_A_PIN_PARENT_PIN] = NLA_POLICY_NESTED(dpll_pin_parent_pin_nl_policy),
 	[DPLL_A_PIN_PHASE_ADJUST] = { .type = NLA_S32, },
 	[DPLL_A_PIN_ESYNC_FREQUENCY] = { .type = NLA_U64, },
+	[DPLL_A_PIN_REFERENCE_SYNC] = NLA_POLICY_NESTED(dpll_reference_sync_nl_policy),
 };
 
 /* Ops table for dpll */
@@ -140,7 +146,7 @@ static const struct genl_split_ops dpll_nl_ops[] = {
 		.doit		= dpll_nl_pin_set_doit,
 		.post_doit	= dpll_pin_post_doit,
 		.policy		= dpll_pin_set_nl_policy,
-		.maxattr	= DPLL_A_PIN_ESYNC_FREQUENCY,
+		.maxattr	= DPLL_A_PIN_REFERENCE_SYNC,
 		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
 	},
 };

drivers/dpll/dpll_nl.h

@@ -14,6 +14,7 @@
 /* Common nested types */
 extern const struct nla_policy dpll_pin_parent_device_nl_policy[DPLL_A_PIN_PHASE_OFFSET + 1];
 extern const struct nla_policy dpll_pin_parent_pin_nl_policy[DPLL_A_PIN_STATE + 1];
+extern const struct nla_policy dpll_reference_sync_nl_policy[DPLL_A_PIN_STATE + 1];
 
 int dpll_lock_doit(const struct genl_split_ops *ops, struct sk_buff *skb,
 		   struct genl_info *info);

include/uapi/linux/dpll.h

@@ -249,6 +249,7 @@ enum dpll_a_pin {
 	DPLL_A_PIN_ESYNC_FREQUENCY,
 	DPLL_A_PIN_ESYNC_FREQUENCY_SUPPORTED,
 	DPLL_A_PIN_ESYNC_PULSE,
+	DPLL_A_PIN_REFERENCE_SYNC,
 
 	__DPLL_A_PIN_MAX,
 	DPLL_A_PIN_MAX = (__DPLL_A_PIN_MAX - 1)