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netutils/ptpd: phase-lock hardware clock via POSIX clock_adjtime.

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When state->clockid is configured to a hardware PTP clock device
(e.g., /dev/ptp0) instead of CLOCK_REALTIME, ptp_adjtime() previously
passed only the measured frequency drift (-ppb) to clock_adjtime(),
ignoring the residual phase offset (delta_ns / adjustment_ns).
As a result, while the hardware counter tracked frequency, its phase
was never pulled into alignment with the master clock.

Convert delta_ns (which combines frequency drift and current phase error
clamped to max_adjust_ns) to ppb over CONFIG_CLOCK_ADJTIME_PERIOD_MS,
acting as a proportional-integral (PI) phase servo. This drives the
hardware clock to phase lock with the master via POSIX clock_adjtime()
using ADJ_FREQUENCY without requiring proprietary ioctl calls.

Assisted-by: Claude:claude-sonnet-5
Assisted-by: Gemini:gemini-3.8-flash-medium
Signed-off-by: Daniel P. Carvalho <danieloak@gmail.com>
This commit is contained in:
Daniel P. Carvalho 2026-09-17 17:50:44 -03:00 • committed by Xiang Xiao
parent e8fa49dc72
commit 6d10b44bc1
1 changed files with 25 additions and 2 deletions
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27
netutils/ptpd/ptpd.c
View file

@ -30,9 +30,10 @@
#include <stdbool.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/timex.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
@ -441,9 +442,31 @@ static int ptp_adjtime(FAR struct ptp_state_s *state, int64_t delta_ns,
else
{
struct timex buf;
int64_t hw_ppb;
const int64_t slew_limit_ppb =
CONFIG_CLOCK_ADJTIME_SLEWLIMIT_PPM * 1000;
/* delta_ns passed here is adjustment_ns, which already
* combines frequency drift and current phase error clamped
* to max_adjust_ns. Converting it to ppb over
* CONFIG_CLOCK_ADJTIME_PERIOD_MS produces the rate needed to
* pull the hardware counter into phase lock.
*/
hw_ppb = delta_ns * MSEC_PER_SEC /
CONFIG_CLOCK_ADJTIME_PERIOD_MS;
if (hw_ppb > slew_limit_ppb)
{
hw_ppb = slew_limit_ppb;
}
else if (hw_ppb < -slew_limit_ppb)
{
hw_ppb = -slew_limit_ppb;
}
memset(&buf, 0, sizeof(buf));
buf.freq = (long)(-ppb * 65536 / 1000);
buf.freq = hw_ppb * 65536 / 1000;
buf.modes = ADJ_FREQUENCY;
return clock_adjtime(state->clockid, &buf);