[PATCHv1 next] ptp: update gettimex64 to provide ts optionally in mono-raw base.

[Mahesh Bandewar <maheshb@google.com>]

The current implementation of PTP_SYS_OFFSET_EXTENDED provides
PHC reads in the form of [pre-TS, PHC, post-TS]. These pre and
post timestamps are useful to measure the width of the PHC read.
However, the current implementation provides these timestamps in
CLOCK_REALTIME only. Since CLOCK_REALTIME is disciplined by NTP
or NTP-like service(s), the value is subjected to change. This
makes some applications that are very sensitive to time change
have these timestamps delivered in different time-base.

This patch updates the gettimex64 / ioctl op PTP_SYS_OFFSET_EXTENDED
to provide these (sandwich) timestamps optionally in
CLOCK_MONOTONIC_RAW timebase while maintaining the default behavior
or giving them in CLOCK_REALTIME.

~# testptp -d /dev/ptp0 -x 3 -y raw
extended timestamp request returned 3 samples
sample # 0: mono-raw time before: 371.548640128
            phc time: 371.579671788
            mono-raw time after: 371.548640912
sample # 1: mono-raw time before: 371.548642104
            phc time: 371.579673346
            mono-raw time after: 371.548642490
sample # 2: mono-raw time before: 371.548643320
            phc time: 371.579674652
            mono-raw time after: 371.548643756
~# testptp -d /dev/ptp0 -x 3
extended timestamp request returned 3 samples
sample # 0: system time before: 1713243413.403474250
            phc time: 385.699915490
            system time after: 1713243413.403474948
sample # 1: system time before: 1713243413.403476220
            phc time: 385.699917168
            system time after: 1713243413.403476642
sample # 2: system time before: 1713243413.403477555
            phc time: 385.699918442
            system time after: 1713243413.403477961
~#

Signed-off-by: Mahesh Bandewar <maheshb@google.com>
---
 drivers/ptp/ptp_chardev.c        |  5 ++++-
 include/linux/ptp_clock_kernel.h | 30 ++++++++++++++++++++++++++----
 include/uapi/linux/ptp_clock.h   |  7 ++++++-
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 7513018c9f9a..34cd0ab79b10 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -359,10 +359,13 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
 			break;
 		}
 		if (extoff->n_samples > PTP_MAX_SAMPLES
-		    || extoff->rsv[0] || extoff->rsv[1] || extoff->rsv[2]) {
+		    || extoff->rsv[0] || extoff->rsv[1]
+		    || (extoff->clockid != CLOCK_REALTIME
+			&& extoff->clockid != CLOCK_MONOTONIC_RAW)) {
 			err = -EINVAL;
 			break;
 		}
+		sts.clockid = extoff->clockid;
 		for (i = 0; i < extoff->n_samples; i++) {
 			err = ptp->info->gettimex64(ptp->info, &ts, &sts);
 			if (err)
diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index 6e4b8206c7d0..7563da6db09b 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -47,10 +47,12 @@ struct system_device_crosststamp;
  * struct ptp_system_timestamp - system time corresponding to a PHC timestamp
  * @pre_ts: system timestamp before capturing PHC
  * @post_ts: system timestamp after capturing PHC
+ * @clockid: clockid used for cpaturing timestamp
  */
 struct ptp_system_timestamp {
 	struct timespec64 pre_ts;
 	struct timespec64 post_ts;
+	clockid_t clockid;
 };
 
 /**
@@ -457,14 +459,34 @@ static inline ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp,
 
 static inline void ptp_read_system_prets(struct ptp_system_timestamp *sts)
 {
-	if (sts)
-		ktime_get_real_ts64(&sts->pre_ts);
+	if (sts) {
+		switch (sts->clockid) {
+		case CLOCK_REALTIME:
+			ktime_get_real_ts64(&sts->pre_ts);
+			break;
+		case CLOCK_MONOTONIC_RAW:
+			ktime_get_raw_ts64(&sts->pre_ts);
+			break;
+		default:
+			break;
+		}
+	}
 }
 
 static inline void ptp_read_system_postts(struct ptp_system_timestamp *sts)
 {
-	if (sts)
-		ktime_get_real_ts64(&sts->post_ts);
+	if (sts) {
+		switch (sts->clockid) {
+		case CLOCK_REALTIME:
+			ktime_get_real_ts64(&sts->post_ts);
+			break;
+		case CLOCK_MONOTONIC_RAW:
+			ktime_get_raw_ts64(&sts->post_ts);
+			break;
+		default:
+			break;
+		}
+	}
 }
 
 #endif
diff --git a/include/uapi/linux/ptp_clock.h b/include/uapi/linux/ptp_clock.h
index 053b40d642de..fc5825e72330 100644
--- a/include/uapi/linux/ptp_clock.h
+++ b/include/uapi/linux/ptp_clock.h
@@ -157,7 +157,12 @@ struct ptp_sys_offset {
 
 struct ptp_sys_offset_extended {
 	unsigned int n_samples; /* Desired number of measurements. */
-	unsigned int rsv[3];    /* Reserved for future use. */
+	/* The original implementation provided timestamps (always) in
+	 * REALTIME clock-base. Since CLOCK_REALTIME is 0, adding
+	 * clockid doesn't break backward compatibility.
+	 */
+	clockid_t clockid;	/* One of the supported clock-ids */
+	unsigned int rsv[2];    /* Reserved for future use. */
 	/*
 	 * Array of [system, phc, system] time stamps. The kernel will provide
 	 * 3*n_samples time stamps.
-- 
2.44.0.683.g7961c838ac-goog