ptp: add kernel API ptp_convert_timestamp()

Add kernel API ptp_convert_timestamp() to convert raw hardware timestamp
to a specified ptp vclock time.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>

drivers/ptp/ptp_vclock.c

@@ -176,3 +176,37 @@ int ptp_get_vclocks_index(int pclock_index, int *vclock_index)
 	return num;
 }
 EXPORT_SYMBOL(ptp_get_vclocks_index);
+
+void ptp_convert_timestamp(struct skb_shared_hwtstamps *hwtstamps,
+			   int vclock_index)
+{
+	char name[PTP_CLOCK_NAME_LEN] = "";
+	struct ptp_vclock *vclock;
+	struct ptp_clock *ptp;
+	unsigned long flags;
+	struct device *dev;
+	u64 ns;
+
+	snprintf(name, PTP_CLOCK_NAME_LEN, "ptp%d", vclock_index);
+	dev = class_find_device_by_name(ptp_class, name);
+	if (!dev)
+		return;
+
+	ptp = dev_get_drvdata(dev);
+	if (!ptp->vclock_flag) {
+		put_device(dev);
+		return;
+	}
+
+	vclock = info_to_vclock(ptp->info);
+
+	ns = ktime_to_ns(hwtstamps->hwtstamp);
+
+	spin_lock_irqsave(&vclock->lock, flags);
+	ns = timecounter_cyc2time(&vclock->tc, ns);
+	spin_unlock_irqrestore(&vclock->lock, flags);
+
+	put_device(dev);
+	hwtstamps->hwtstamp = ns_to_ktime(ns);
+}
+EXPORT_SYMBOL(ptp_convert_timestamp);

include/linux/ptp_clock_kernel.h

@@ -12,6 +12,7 @@
 #include <linux/pps_kernel.h>
 #include <linux/ptp_clock.h>
 #include <linux/timecounter.h>
+#include <linux/skbuff.h>
 
 #define PTP_CLOCK_NAME_LEN	32
 /**
@@ -316,6 +317,15 @@ void ptp_cancel_worker_sync(struct ptp_clock *ptp);
  */
 int ptp_get_vclocks_index(int pclock_index, int *vclock_index);
 
+/**
+ * ptp_convert_timestamp() - convert timestamp to a ptp vclock time
+ *
+ * @hwtstamps:    skb_shared_hwtstamps structure pointer
+ * @vclock_index: phc index of ptp vclock.
+ */
+void ptp_convert_timestamp(struct skb_shared_hwtstamps *hwtstamps,
+			   int vclock_index);
+
 #else
 static inline struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 						   struct device *parent)
@@ -337,6 +347,9 @@ static inline void ptp_cancel_worker_sync(struct ptp_clock *ptp)
 { }
 static int ptp_get_vclocks_index(int pclock_index, int *vclock_index)
 { return 0; }
+static void ptp_convert_timestamp(struct skb_shared_hwtstamps *hwtstamps,
+				  int vclock_index)
+{ }
 
 #endif