/*
 * phc_phase_log - 1Hz logger of CLOCK_REALTIME vs ENA PHC, plus kernel
 * NTP discipline state, for chrony A/B benchmarking.
 *
 * Per sample:
 *   - PTP_SYS_OFFSET_EXTENDED (n samples, keep the tightest bracket):
 *     realtime - phc, with bracket width as quality bound
 *   - adjtimex() readback: freq, offset, status
 *   - /sys/kernel/debug/tk_sample: real_ns snapshot_err_ns ntp_error
 *     mult ntp_err_mult ntp_err_frac
 *
 * CSV to stdout (append via shell):
 *   iso8601,phc_offset_ns,bracket_ns,adj_freq_scaled,adj_offset,adj_status,
 *   snap_err_ns,ntp_error,mult,ntp_err_mult,ntp_err_frac
 *
 * Usage: phc_phase_log [/dev/ptp0 [interval_s]] >> phc_phase.csv
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/timex.h>
#include <linux/ptp_clock.h>

#define NSAMPLES 5

static int64_t ts_ns(const struct ptp_clock_time *t)
{
	return (int64_t)t->sec * 1000000000LL + t->nsec;
}

int main(int argc, char **argv)
{
	const char *dev = argc > 1 ? argv[1] : "/dev/ptp0";
	int interval = argc > 2 ? atoi(argv[2]) : 1;
	int fd = open(dev, O_RDONLY);
	int tkfd;

	if (fd < 0) {
		perror(dev);
		return 1;
	}
	tkfd = open("/sys/kernel/debug/tk_sample", O_RDONLY);

	printf("timestamp,phc_offset_ns,bracket_ns,adj_freq_scaled,"
	       "adj_offset,adj_status,snap_err_ns,ntp_error,mult,"
	       "ntp_err_mult,ntp_err_frac\n");

	for (;;) {
		struct ptp_sys_offset_extended sox = { .n_samples = NSAMPLES };
		int64_t best_off = 0, best_br = INT64_MAX;
		char tkbuf[128] = "0 0 0 0 0 0";
		struct timex tx = { 0 };
		char tbuf[64];
		struct tm tm;
		time_t now;

		if (ioctl(fd, PTP_SYS_OFFSET_EXTENDED, &sox) < 0) {
			perror("PTP_SYS_OFFSET_EXTENDED");
			sleep(interval);
			continue;
		}
		for (unsigned int i = 0; i < sox.n_samples; i++) {
			int64_t t1 = ts_ns(&sox.ts[i][0]);
			int64_t tp = ts_ns(&sox.ts[i][1]);
			int64_t t2 = ts_ns(&sox.ts[i][2]);

			if (t2 - t1 < best_br) {
				best_br = t2 - t1;
				best_off = (t1 + t2) / 2 - tp;
			}
		}

		adjtimex(&tx);

		if (tkfd >= 0) {
			ssize_t n = pread(tkfd, tkbuf, sizeof(tkbuf) - 1, 0);

			if (n > 0) {
				tkbuf[n] = 0;
				tkbuf[strcspn(tkbuf, "\n")] = 0;
			}
		}
		/* tk_sample: real snap_err ntp_error mult err_mult frac */
		long long tk_real, tk_snap_err, tk_ntp_error, tk_frac;
		unsigned int tk_mult, tk_err_mult;
		if (sscanf(tkbuf, "%lld %lld %lld %u %u %lld", &tk_real,
			   &tk_snap_err, &tk_ntp_error, &tk_mult,
			   &tk_err_mult, &tk_frac) != 6)
			tk_snap_err = tk_ntp_error = tk_mult = tk_err_mult =
				tk_frac = 0;

		time(&now);
		gmtime_r(&now, &tm);
		strftime(tbuf, sizeof(tbuf), "%Y-%m-%dT%H:%M:%SZ", &tm);
		printf("%s,%lld,%lld,%ld,%ld,0x%x,%lld,%lld,%u,%u,%lld\n",
		       tbuf, (long long)best_off, (long long)best_br,
		       tx.freq, tx.offset, tx.status, tk_snap_err,
		       tk_ntp_error, tk_mult, tk_err_mult, tk_frac);
		fflush(stdout);
		sleep(interval);
	}
}