From: Vincent Cheng <vincent.cheng...@renesas.com>
When clock stepping is unable to happen instantaneously the subsequent
timestamps after a clock step does not reflect the step result and
undesired clock freq and step adjustments will occur.
When using ts2phc to synchronize timestamping clock using external
1 PPS, it could take up to 1 second for the timestamps to reflect the
clock step.
step_window, when set, indicates the time in seconds after a clock
step in which the clock servo will not do any frequency or step
adjustments.
Signed-off-by: Vincent Cheng <vincent.cheng...@renesas.com>
---
clock.c | 40 ++++++++++++++++++++++++++++++++++++++++
config.c | 1 +
ptp4l.8 | 8 ++++++++
3 files changed, 49 insertions(+)
diff --git a/clock.c b/clock.c
index a34737a..c03d548 100644
--- a/clock.c
+++ b/clock.c
@@ -20,6 +20,7 @@
#include <time.h>
#include <linux/net_tstamp.h>
#include <poll.h>
+#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
@@ -132,6 +133,8 @@ struct clock {
struct interface *udsif;
LIST_HEAD(clock_subscribers_head, clock_subscriber) subscribers;
struct monitor *slave_event_monitor;
+ int step_window;
+ timer_t step_timer_id;
};
struct clock the_clock;
@@ -141,6 +144,13 @@ static int clock_resize_pollfd(struct clock *c, int
new_nports);
static void clock_remove_port(struct clock *c, struct port *p);
static void clock_stats_display(struct clock_stats *s);
+static void clock_clear_free_running(union sigval callback_data)
+{
+ struct clock *c = (struct clock *)(callback_data.sival_ptr);
+
+ c->free_running = 0;
+}
+
static void remove_subscriber(struct clock_subscriber *s)
{
LIST_REMOVE(s, list);
@@ -286,6 +296,7 @@ void clock_destroy(struct clock *c)
if (c->sanity_check) {
clockcheck_destroy(c->sanity_check);
}
+ timer_delete(c->step_timer_id);
memset(c, 0, sizeof(*c));
msg_cleanup();
tc_cleanup();
@@ -897,6 +908,7 @@ struct clock *clock_create(enum clock_type type, struct
config *config,
unsigned char oui[OUI_LEN];
struct interface *iface;
struct timespec ts;
+ struct sigevent se;
int sfl;
clock_gettime(CLOCK_REALTIME, &ts);
@@ -1194,6 +1206,18 @@ struct clock *clock_create(enum clock_type type, struct
config *config,
return NULL;
}
+ /* Set up timer expire notification mechanism */
+ se.sigev_notify = SIGEV_THREAD;
+ se.sigev_value.sival_ptr = (void *)c;
+ se.sigev_notify_function = clock_clear_free_running;
+ se.sigev_notify_attributes = NULL;
+
+ if (timer_create(CLOCK_MONOTONIC, &se, &c->step_timer_id)) {
+ pr_err("failed to create step timer_id");
+ return NULL;
+ }
+ c->step_window = config_get_int(config, NULL, "step_window");
+
/* Create the ports. */
STAILQ_FOREACH(iface, &config->interfaces, list) {
if (clock_add_port(c, phc_device, phc_index, timestamping,
iface)) {
@@ -1696,6 +1720,21 @@ int clock_switch_phc(struct clock *c, int phc_index)
return 0;
}
+static void clock_step_window(struct clock *c)
+{
+ struct itimerspec tmo = {
+ {0, 0}, {0, 0}
+ };
+
+ if (!c->step_window)
+ return;
+
+ c->free_running = 1;
+
+ tmo.it_value.tv_sec = c->step_window;
+ timer_settime(c->step_timer_id, 0, &tmo, 0);
+}
+
static void clock_synchronize_locked(struct clock *c, double adj)
{
clockadj_set_freq(c->clkid, -adj);
@@ -1748,6 +1787,7 @@ enum servo_state clock_synchronize(struct clock *c, tmv_t
ingress, tmv_t origin)
case SERVO_JUMP:
clockadj_set_freq(c->clkid, -adj);
clockadj_step(c->clkid, -tmv_to_nanoseconds(c->master_offset));
+ clock_step_window(c);
c->ingress_ts = tmv_zero();
if (c->sanity_check) {
clockcheck_set_freq(c->sanity_check, -adj);
diff --git a/config.c b/config.c
index 4095b33..2b74bc8 100644
--- a/config.c
+++ b/config.c
@@ -303,6 +303,7 @@ struct config_item config_tab[] = {
GLOB_ITEM_INT("slaveOnly", 0, 0, 1), /*deprecated*/
GLOB_ITEM_INT("socket_priority", 0, 0, 15),
GLOB_ITEM_DBL("step_threshold", 0.0, 0.0, DBL_MAX),
+ GLOB_ITEM_INT("step_window", 0, 0, UINT8_MAX),
GLOB_ITEM_INT("summary_interval", 0, INT_MIN, INT_MAX),
PORT_ITEM_INT("syncReceiptTimeout", 0, 0, UINT8_MAX),
GLOB_ITEM_INT("tc_spanning_tree", 0, 0, 1),
diff --git a/ptp4l.8 b/ptp4l.8
index 260aae3..0923bf3 100644
--- a/ptp4l.8
+++ b/ptp4l.8
@@ -699,6 +699,14 @@ one-second offset slowly by changing the clock frequency
(unless the
option is set to correct such offset by stepping).
Relevant only with software time stamping. The default is 1 (enabled).
.TP
+.B step_window
+When set, indicates the time in seconds after a clock step that the clock will
+not do any frequency or step adjustments.
+This is used in situations where clock stepping is unable to happen
+instantaneously and so there is a lag before the timestamps can settle
+properly reflect the clock step.
+The default is 0 (disabled).
+.TP
.B timeSource
The time source is a single byte code that gives an idea of the kind
of local clock in use. The value is purely informational, having no
--
2.7.4
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