ptp: add helpers to get the phc_index by of_node or dev

Some Ethernet controllers do not have an integrated PTP timer function.
Instead, the PTP timer is a separated device and provides PTP hardware
clock to the Ethernet controller to use. Therefore, the Ethernet
controller driver needs to obtain the PTP clock's phc_index in its
ethtool_ops::get_ts_info(). Currently, most drivers implement this in
the following ways.

1. The PTP device driver adds a custom API and exports it to the Ethernet
controller driver.
2. The PTP device driver adds private data to its device structure. So
the private data structure needs to be exposed to the Ethernet controller
driver.

When registering the ptp clock, ptp_clock_register() always saves the
ptp_clock pointer to the private data of ptp_clock::dev. Therefore, as
long as ptp_clock::dev is obtained, the phc_index can be obtained. So
the following generic APIs can be added to the ptp driver to obtain the
phc_index.

1. ptp_clock_index_by_dev(): Obtain the phc_index by the device pointer
of the PTP device.
2.ptp_clock_index_by_of_node(): Obtain the phc_index by the of_node
pointer of the PTP device.

Also, we can add another API like ptp_clock_index_by_fwnode() to get the
phc_index by fwnode of PTP device. However, this API is not used in this
patch set, so it is better to add it when needed.

Suggested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20250829050615.1247468-4-wei.fang@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index 3d089bd4d5e9..7dd7951b23d5 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -361,6 +361,24 @@ extern void ptp_clock_event(struct ptp_clock *ptp,
 extern int ptp_clock_index(struct ptp_clock *ptp);
 
 /**
+ * ptp_clock_index_by_of_node() - obtain the device index of
+ * a PTP clock based on the PTP device of_node
+ *
+ * @np:    The device of_node pointer of the PTP device.
+ * Return: The PHC index on success or -1 on failure.
+ */
+int ptp_clock_index_by_of_node(struct device_node *np);
+
+/**
+ * ptp_clock_index_by_dev() - obtain the device index of
+ * a PTP clock based on the PTP device.
+ *
+ * @parent:    The parent device (PTP device) pointer of the PTP clock.
+ * Return: The PHC index on success or -1 on failure.
+ */
+int ptp_clock_index_by_dev(struct device *parent);
+
+/**
  * ptp_find_pin() - obtain the pin index of a given auxiliary function
  *
  * The caller must hold ptp_clock::pincfg_mux.  Drivers do not have
@@ -425,6 +443,10 @@ static inline void ptp_clock_event(struct ptp_clock *ptp,
 { }
 static inline int ptp_clock_index(struct ptp_clock *ptp)
 { return -1; }
+static inline int ptp_clock_index_by_of_node(struct device_node *np)
+{ return -1; }
+static inline int ptp_clock_index_by_dev(struct device *parent)
+{ return -1; }
 static inline int ptp_find_pin(struct ptp_clock *ptp,
 			       enum ptp_pin_function func, unsigned int chan)
 { return -1; }