ptp: introduce PTP_CLOCK_EXTOFF event for the measured external offset

This change is for the PHC devices that can measure the phase offset
between PHC signal and the external signal, such as the 1PPS signal of
GNSS. Reporting PTP_CLOCK_EXTOFF to user space will be piggy-backed to
the existing ptp_extts_event so that application such as ts2phc can
poll the external offset the same way as extts. Hence, ts2phc can use
the offset to achieve the alignment between PHC and the external signal
by the help of either SW or HW filters.

Signed-off-by: Min Li <[e-mail]>
Acked-by: Richard Cochran <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/ptp/ptp_clock.c

···
 				       struct ptp_clock_event *src)
 {
 	struct ptp_extts_event *dst;
+	struct timespec64 offset_ts;
 	unsigned long flags;
 	s64 seconds;
 	u32 remainder;
 
-	seconds = div_u64_rem(src->timestamp, 1000000000, &remainder);
+	if (src->type == PTP_CLOCK_EXTTS) {
+		seconds = div_u64_rem(src->timestamp, 1000000000, &remainder);
+	} else if (src->type == PTP_CLOCK_EXTOFF) {
+		offset_ts = ns_to_timespec64(src->offset);
+		seconds = offset_ts.tv_sec;
+		remainder = offset_ts.tv_nsec;
+	} else {
+		WARN(1, "%s: unknown type %d\n", __func__, src->type);
+		return;
+	}
 
 	spin_lock_irqsave(&queue->lock, flags);
 
 	dst = &queue->buf[queue->tail];
 	dst->index = src->index;
+	dst->flags = PTP_EXTTS_EVENT_VALID;
 	dst->t.sec = seconds;
 	dst->t.nsec = remainder;
+	if (src->type == PTP_CLOCK_EXTOFF)
+		dst->flags |= PTP_EXT_OFFSET;
 
 	/* Both WRITE_ONCE() are paired with READ_ONCE() in queue_cnt() */
 	if (!queue_free(queue))
···
 		break;
 
 	case PTP_CLOCK_EXTTS:
+	case PTP_CLOCK_EXTOFF:
 		/* Enqueue timestamp on selected queues */
 		spin_lock_irqsave(&ptp->tsevqs_lock, flags);
 		list_for_each_entry(tsevq, &ptp->tsevqs, qlist) {

include/linux/ptp_clock_kernel.h

···
 enum ptp_clock_events {
 	PTP_CLOCK_ALARM,
 	PTP_CLOCK_EXTTS,
+	PTP_CLOCK_EXTOFF,
 	PTP_CLOCK_PPS,
 	PTP_CLOCK_PPSUSR,
 };
···
  * @type:  One of the ptp_clock_events enumeration values.
  * @index: Identifies the source of the event.
  * @timestamp: When the event occurred (%PTP_CLOCK_EXTTS only).
+ * @offset:    When the event occurred (%PTP_CLOCK_EXTOFF only).
  * @pps_times: When the event occurred (%PTP_CLOCK_PPSUSR only).
  */
 
···
 	int index;
 	union {
 		u64 timestamp;
+		s64 offset;
 		struct pps_event_time pps_times;
 	};
 };

include/uapi/linux/ptp_clock.h

···
 #define PTP_RISING_EDGE    (1<<1)
 #define PTP_FALLING_EDGE   (1<<2)
 #define PTP_STRICT_FLAGS   (1<<3)
+#define PTP_EXT_OFFSET     (1<<4)
 #define PTP_EXTTS_EDGES    (PTP_RISING_EDGE | PTP_FALLING_EDGE)
 
 /*
···
 #define PTP_EXTTS_VALID_FLAGS	(PTP_ENABLE_FEATURE |	\
 				 PTP_RISING_EDGE |	\
 				 PTP_FALLING_EDGE |	\
-				 PTP_STRICT_FLAGS)
+				 PTP_STRICT_FLAGS |	\
+				 PTP_EXT_OFFSET)
 
 /*
  * flag fields valid for the original PTP_EXTTS_REQUEST ioctl.
···
 #define PTP_EXTTS_V1_VALID_FLAGS	(PTP_ENABLE_FEATURE |	\
 					 PTP_RISING_EDGE |	\
 					 PTP_FALLING_EDGE)
+
+/*
+ * flag fields valid for the ptp_extts_event report.
+ */
+#define PTP_EXTTS_EVENT_VALID	(PTP_ENABLE_FEATURE)
 
 /*
  * Bits of the ptp_perout_request.flags field:
···
 #define PTP_MASK_EN_SINGLE  _IOW(PTP_CLK_MAGIC, 20, unsigned int)
 
 struct ptp_extts_event {
-	struct ptp_clock_time t; /* Time event occured. */
+	struct ptp_clock_time t; /* Time event occurred. */
 	unsigned int index;      /* Which channel produced the event. */
-	unsigned int flags;      /* Reserved for future use. */
+	unsigned int flags;      /* Event type. */
 	unsigned int rsv[2];     /* Reserved for future use. */
 };