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[PATCH v2 0/1] Add PTP cross-timestamp to the PTP driver interface

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  [PATCH v2 0/1] Add PTP cross-timestamp to the PTP driver interface Christopher Hall <christopher.s.hall@intel.com> - 2015-07-03 03:20 +0200
    [PATCH v2 1/1] Added additional callback to ptp_clock_info: Christopher Hall <christopher.s.hall@intel.com> - 2015-07-03 03:20 +0200

#1176280 — [PATCH v2 0/1] Add PTP cross-timestamp to the PTP driver interface

This patch allows system and device time ("cross-timestamp") to be performed 
by the driver. Currently, the cross-timestamping is performed in the
PTP_SYS_OFFSET ioctl.  The PTP clock driver reads gettimeofday() and the 
gettime64() callback provided by the driver. The cross-timestamp is best 
effort where the latency between the capture of system time 
(getnstimeofday()) and the device time (driver callback) may be significant.

This patch adds an additional callback getsynctime64(). Which will be called 
when the driver is able to perform a more accurate, implementation specific 
cross-timestamping.  For example, future network devices that implement 
PCIE PTM will be able to precisely correlate the device clock with the system 
clock with virtually zero latency between captures.  This added callback can 
be used by the driver to expose this functionality.

The callback, getsynctime64(), will only be called when defined and
n_samples == 1 because the driver returns only 1 cross-timestamp where 
multiple samples cannot be chained together.

This patch also adds to the capabilities ioctl (PTP_CLOCK_GETCAPS), allowing 
applications to query whether or not drivers implement the getsynctime 
callback, providing more precise cross timestamping.

Christopher Hall (1):
  Added additional callback to ptp_clock_info:

 drivers/ptp/ptp_chardev.c        | 29 +++++++++++++++++++++--------
 include/linux/ptp_clock_kernel.h |  8 ++++++++
 include/uapi/linux/ptp_clock.h   |  4 +++-
 3 files changed, 32 insertions(+), 9 deletions(-)

-- 
1.9.1

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#1176281 — [PATCH v2 1/1] Added additional callback to ptp_clock_info:

* getsynctime64()

This takes 2 arguments referring to system and device time

With this callback drivers may provide both system time and device time
to ensure precise correlation

Modified PTP_SYS_OFFSET ioctl in PTP clock driver to use the above
callback if it's available

Added capability (PTP_CLOCK_GETCAPS) for checking whether driver supports
precise timestamping

Signed-off-by: Christopher Hall <christopher.s.hall@intel.com>
---
 drivers/ptp/ptp_chardev.c        | 29 +++++++++++++++++++++--------
 include/linux/ptp_clock_kernel.h |  8 ++++++++
 include/uapi/linux/ptp_clock.h   |  4 +++-
 3 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index da7bae9..2a83aea 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -124,7 +124,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
 	struct ptp_clock_info *ops = ptp->info;
 	struct ptp_clock_time *pct;
-	struct timespec64 ts;
+	struct timespec64 ts, systs;
 	int enable, err = 0;
 	unsigned int i, pin_index;
 
@@ -138,6 +138,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 		caps.n_per_out = ptp->info->n_per_out;
 		caps.pps = ptp->info->pps;
 		caps.n_pins = ptp->info->n_pins;
+		caps.precise_timestamping = ptp->info->getsynctime64 != NULL;
 		if (copy_to_user((void __user *)arg, &caps, sizeof(caps)))
 			err = -EFAULT;
 		break;
@@ -196,19 +197,31 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 			break;
 		}
 		pct = &sysoff->ts[0];
-		for (i = 0; i < sysoff->n_samples; i++) {
-			getnstimeofday64(&ts);
+		if (ptp->info->getsynctime64 && sysoff->n_samples == 1) {
+			ptp->info->getsynctime64(ptp->info, &ts, &systs);
+			pct->sec = systs.tv_sec;
+			pct->nsec = systs.tv_nsec;
+			pct++;
 			pct->sec = ts.tv_sec;
 			pct->nsec = ts.tv_nsec;
 			pct++;
-			ptp->info->gettime64(ptp->info, &ts);
+			pct->sec = systs.tv_sec;
+			pct->nsec = systs.tv_nsec;
+		} else {
+			for (i = 0; i < sysoff->n_samples; i++) {
+				getnstimeofday64(&ts);
+				pct->sec = ts.tv_sec;
+				pct->nsec = ts.tv_nsec;
+				pct++;
+				ptp->info->gettime64(ptp->info, &ts);
+				pct->sec = ts.tv_sec;
+				pct->nsec = ts.tv_nsec;
+				pct++;
+			}
+			getnstimeofday64(&ts);
 			pct->sec = ts.tv_sec;
 			pct->nsec = ts.tv_nsec;
-			pct++;
 		}
-		getnstimeofday64(&ts);
-		pct->sec = ts.tv_sec;
-		pct->nsec = ts.tv_nsec;
 		if (copy_to_user((void __user *)arg, sysoff, sizeof(*sysoff)))
 			err = -EFAULT;
 		break;
diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index b8b7306..344f129 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -67,6 +67,11 @@ struct ptp_clock_request {
  * @gettime64:  Reads the current time from the hardware clock.
  *              parameter ts: Holds the result.
  *
+ * @getsynctime64:  Reads the current time from the hardware clock and system
+ *                  clock simultaneously.
+ *                  parameter dev: Holds the device time
+ *                  parameter sys: Holds the system time
+ *
  * @settime64:  Set the current time on the hardware clock.
  *              parameter ts: Time value to set.
  *
@@ -105,6 +110,9 @@ struct ptp_clock_info {
 	int (*adjfreq)(struct ptp_clock_info *ptp, s32 delta);
 	int (*adjtime)(struct ptp_clock_info *ptp, s64 delta);
 	int (*gettime64)(struct ptp_clock_info *ptp, struct timespec64 *ts);
+	int (*getsynctime64)
+		(struct ptp_clock_info *ptp, struct timespec64 *dev,
+		 struct timespec64 *sys);
 	int (*settime64)(struct ptp_clock_info *p, const struct timespec64 *ts);
 	int (*enable)(struct ptp_clock_info *ptp,
 		      struct ptp_clock_request *request, int on);
diff --git a/include/uapi/linux/ptp_clock.h b/include/uapi/linux/ptp_clock.h
index f0b7bfe..421b637 100644
--- a/include/uapi/linux/ptp_clock.h
+++ b/include/uapi/linux/ptp_clock.h
@@ -51,7 +51,9 @@ struct ptp_clock_caps {
 	int n_per_out; /* Number of programmable periodic signals. */
 	int pps;       /* Whether the clock supports a PPS callback. */
 	int n_pins;    /* Number of input/output pins. */
-	int rsv[14];   /* Reserved for future use. */
+	/* Whether the clock supports precise system-device cross timestamps */
+	int precise_timestamping;
+	int rsv[13];   /* Reserved for future use. */
 };
 
 struct ptp_extts_request {
-- 
1.9.1

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