pps/ptp: Allow PHC devices to adjust PPS events for known delay

Initial version by Stuart Hodgson <smhodgson@solarflare.com>

Some PHC device drivers may deliver PPS events with a significant
and variable delay, but still be able to measure precisely what
that delay is.

Add a pps_sub_ts() function for subtracting a delay from the
timestamp(s) in a PPS event, and a PTP event type (PTP_CLOCK_PPSUSR)
for which the caller provides a complete PPS event.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/ptp/ptp_clock.c

@@ -300,6 +300,11 @@ void ptp_clock_event(struct ptp_clock *ptp, struct ptp_clock_event *event)
 		pps_get_ts(&evt);
 		pps_event(ptp->pps_source, &evt, PTP_PPS_EVENT, NULL);
 		break;
+
+	case PTP_CLOCK_PPSUSR:
+		pps_event(ptp->pps_source, &event->pps_times,
+			  PTP_PPS_EVENT, NULL);
+		break;
 	}
 }
 EXPORT_SYMBOL(ptp_clock_event);

include/linux/pps_kernel.h

@@ -116,5 +116,14 @@ static inline void pps_get_ts(struct pps_event_time *ts)
 
 #endif /* CONFIG_NTP_PPS */
 
+/* Subtract known time delay from PPS event time(s) */
+static inline void pps_sub_ts(struct pps_event_time *ts, struct timespec delta)
+{
+	ts->ts_real = timespec_sub(ts->ts_real, delta);
+#ifdef CONFIG_NTP_PPS
+	ts->ts_raw = timespec_sub(ts->ts_raw, delta);
+#endif
+}
+
 #endif /* LINUX_PPS_KERNEL_H */
 

include/linux/ptp_clock_kernel.h

@@ -21,6 +21,7 @@
 #ifndef _PTP_CLOCK_KERNEL_H_
 #define _PTP_CLOCK_KERNEL_H_
 
+#include <linux/pps_kernel.h>
 #include <linux/ptp_clock.h>
 
 
@@ -110,6 +111,7 @@ enum ptp_clock_events {
 	PTP_CLOCK_ALARM,
 	PTP_CLOCK_EXTTS,
 	PTP_CLOCK_PPS,
+	PTP_CLOCK_PPSUSR,
 };
 
 /**
@@ -117,13 +119,17 @@ enum ptp_clock_events {
  *
  * @type:  One of the ptp_clock_events enumeration values.
  * @index: Identifies the source of the event.
- * @timestamp: When the event occured.
+ * @timestamp: When the event occurred (%PTP_CLOCK_EXTTS only).
+ * @pps_times: When the event occurred (%PTP_CLOCK_PPSUSR only).
  */
 
 struct ptp_clock_event {
 	int type;
 	int index;
-	u64 timestamp;
+	union {
+		u64 timestamp;
+		struct pps_event_time pps_times;
+	};
 };
 
 /**