linuxptp/clock.c

/**
 * @file clock.c
 * @note Copyright (C) 2011 Richard Cochran <richardcochran@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#include <errno.h>
#include <poll.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "bmc.h"
#include "clock.h"
#include "foreign.h"
#include "mave.h"
#include "missing.h"
#include "msg.h"
#include "phc.h"
#include "port.h"
#include "servo.h"
#include "print.h"
#include "tlv.h"
#include "uds.h"
#include "util.h"

#define CLK_N_PORTS (MAX_PORTS + 1) /* plus one for the UDS interface */
#define N_CLOCK_PFD (N_POLLFD + 1) /* one extra per port, for the fault timer */
#define MAVE_LENGTH 10
#define POW2_41 ((double)(1ULL << 41))

#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))

struct freq_estimator {
	tmv_t origin1;
	tmv_t ingress1;
	int max_count;
	int count;
};

struct clock {
	clockid_t clkid;
	struct servo *servo;
	struct defaultDS dds;
	struct dataset default_dataset;
	struct currentDS cur;
	struct parent_ds dad;
	struct timePropertiesDS tds;
	struct ClockIdentity ptl[PATH_TRACE_MAX];
	struct foreign_clock *best;
	struct ClockIdentity best_id;
	struct port *port[CLK_N_PORTS];
	struct pollfd pollfd[CLK_N_PORTS*N_CLOCK_PFD];
	int fault_fd[CLK_N_PORTS];
	int8_t fault_timeout[CLK_N_PORTS];
	int nports; /* does not include the UDS port */
	int free_running;
	int freq_est_interval;
	int utc_timescale;
	tmv_t master_offset;
	tmv_t path_delay;
	struct mave *avg_delay;
	struct freq_estimator fest;
	struct time_status_np status;
	double nrr;
	tmv_t c1;
	tmv_t c2;
	tmv_t t1;
	tmv_t t2;
	struct clock_description desc;
};

struct clock the_clock;

static void handle_state_decision_event(struct clock *c);

static int cid_eq(struct ClockIdentity *a, struct ClockIdentity *b)
{
	return 0 == memcmp(a, b, sizeof(*a));
}

void clock_destroy(struct clock *c)
{
	int i;
	for (i = 0; i < c->nports; i++) {
		port_close(c->port[i]);
		close(c->fault_fd[i]);
	}
	port_close(c->port[i]); /*uds*/
	if (c->clkid != CLOCK_REALTIME) {
		phc_close(c->clkid);
	}
	servo_destroy(c->servo);
	mave_destroy(c->avg_delay);
	memset(c, 0, sizeof(*c));
	msg_cleanup();
}

static int clock_fault_timeout(struct clock *c, int index, int set)
{
	int log_seconds = 0;
	unsigned int scale = 0;

	if (set) {
		pr_debug("waiting 2^{%d} seconds to clear fault on port %d",
			 c->fault_timeout[index], index);
		log_seconds = c->fault_timeout[index];
		scale = 1;
	} else {
		pr_debug("clearing fault on port %d", index);
	}
	return set_tmo(c->fault_fd[index], scale, log_seconds);
}

static void clock_freq_est_reset(struct clock *c)
{
	c->fest.origin1 = tmv_zero();
	c->fest.ingress1 = tmv_zero();
	c->fest.count = 0;
};

static void clock_management_send_error(struct port *p,
					struct ptp_message *msg, int error_id)
{
	if (port_management_error(port_identity(p), p, msg, error_id))
		pr_err("failed to send management error status");
}

static int clock_management_get_response(struct clock *c, struct port *p,
					 int id, struct ptp_message *req)
{
	int datalen = 0, err, pdulen, respond = 0;
	struct management_tlv *tlv;
	struct ptp_message *rsp;
	struct time_status_np *tsn;
	struct PortIdentity pid = port_identity(p);

	rsp = port_management_reply(pid, p, req);
	if (!rsp) {
		return 0;
	}
	tlv = (struct management_tlv *) rsp->management.suffix;
	tlv->type = TLV_MANAGEMENT;
	tlv->id = id;

	switch (id) {
	case DEFAULT_DATA_SET:
		memcpy(tlv->data, &c->dds, sizeof(c->dds));
		datalen = sizeof(c->dds);
		respond = 1;
		break;
	case CURRENT_DATA_SET:
		memcpy(tlv->data, &c->cur, sizeof(c->cur));
		datalen = sizeof(c->cur);
		respond = 1;
		break;
	case PARENT_DATA_SET:
		memcpy(tlv->data, &c->dad.pds, sizeof(c->dad.pds));
		datalen = sizeof(c->dad.pds);
		respond = 1;
		break;
	case TIME_PROPERTIES_DATA_SET:
		memcpy(tlv->data, &c->tds, sizeof(c->tds));
		datalen = sizeof(c->tds);
		respond = 1;
		break;
	case TIME_STATUS_NP:
		tsn = (struct time_status_np *) tlv->data;
		tsn->master_offset = c->master_offset;
		tsn->ingress_time = tmv_to_nanoseconds(c->t2);
		tsn->cumulativeScaledRateOffset =
			(UInteger32) (c->status.cumulativeScaledRateOffset +
				      c->nrr * POW2_41 - POW2_41);
		tsn->scaledLastGmPhaseChange = c->status.scaledLastGmPhaseChange;
		tsn->gmTimeBaseIndicator = c->status.gmTimeBaseIndicator;
		tsn->lastGmPhaseChange = c->status.lastGmPhaseChange;
		if (cid_eq(&c->dad.pds.grandmasterIdentity, &c->dds.clockIdentity))
			tsn->gmPresent = 0;
		else
			tsn->gmPresent = 1;
		tsn->gmIdentity = c->dad.pds.grandmasterIdentity;
		datalen = sizeof(*tsn);
		respond = 1;
		break;
	}
	if (respond) {
		tlv->length = sizeof(tlv->id) + datalen;
		pdulen = rsp->header.messageLength + sizeof(*tlv) + datalen;
		rsp->header.messageLength = pdulen;
		rsp->tlv_count = 1;
		err = msg_pre_send(rsp);
		if (err) {
			goto out;
		}
		err = port_forward(p, rsp, pdulen);
	}
out:
	msg_put(rsp);
	return respond ? 1 : 0;
}

static int clock_management_set(struct clock *c, struct port *p,
				int id, struct ptp_message *req)
{
	int respond = 0;
	switch (id) {
	}
	if (respond && !clock_management_get_response(c, p, id, req))
		pr_err("failed to send management set response");
	return respond ? 1 : 0;
}

static int clock_master_lost(struct clock *c)
{
	int i;
	for (i = 0; i < c->nports; i++) {
		if (PS_SLAVE == port_state(c->port[i]))
			return 0;
	}
	return 1;
}

static enum servo_state clock_no_adjust(struct clock *c)
{
	double fui;
	double ratio, freq;
	tmv_t origin2;
	struct freq_estimator *f = &c->fest;
	enum servo_state state = SERVO_UNLOCKED;
	/*
	 * We have clock.t1 as the origin time stamp, and clock.t2 as
	 * the ingress. According to the master's clock, the time at
	 * which the sync arrived is:
	 *
	 *    origin = origin_ts + path_delay + correction
	 *
	 * The ratio of the local clock freqency to the master clock
	 * is estimated by:
	 *
	 *    (ingress_2 - ingress_1) / (origin_2 - origin_1)
	 *
	 * Both of the origin time estimates include the path delay,
	 * but we assume that the path delay is in fact constant.
	 * By leaving out the path delay altogther, we can avoid the
	 * error caused by our imperfect path delay measurement.
	 */
	if (!f->ingress1) {
		f->ingress1 = c->t2;
		f->origin1 = tmv_add(c->t1, tmv_add(c->c1, c->c2));
		return state;
	}
	f->count++;
	if (f->count < f->max_count) {
		return state;
	}
	if (tmv_eq(c->t2, f->ingress1)) {
		pr_warning("bad timestamps in rate ratio calculation");
		return state;
	}
	/*
	 * origin2 = c->t1 (+c->path_delay) + c->c1 + c->c2;
	 */
	origin2 = tmv_add(c->t1, tmv_add(c->c1, c->c2));

	ratio = tmv_dbl(tmv_sub(origin2, f->origin1)) /
		tmv_dbl(tmv_sub(c->t2, f->ingress1));
	freq = (1.0 - ratio) * 1e9;

	pr_info("master offset %10" PRId64 " s%d freq %+7.0f "
		"path delay %9" PRId64,
		c->master_offset, state, freq, c->path_delay);

	fui = 1.0 + (c->status.cumulativeScaledRateOffset + 0.0) / POW2_41;

	pr_debug("peer/local    %.9f", c->nrr);
	pr_debug("fup_info      %.9f", fui);
	pr_debug("product       %.9f", fui * c->nrr);
	pr_debug("sum-1         %.9f", fui + c->nrr - 1.0);
	pr_debug("master/local  %.9f", ratio);
	pr_debug("diff         %+.9f", ratio - (fui + c->nrr - 1.0));

	f->ingress1 = c->t2;
	f->origin1 = origin2;
	f->count = 0;

	return state;
}

static void clock_ppb(clockid_t clkid, double ppb)
{
	struct timex tx;
	memset(&tx, 0, sizeof(tx));
	tx.modes = ADJ_FREQUENCY;
	tx.freq = (long) (ppb * 65.536);
	if (clock_adjtime(clkid, &tx) < 0)
		pr_err("failed to adjust the clock: %m");
}

static double clock_ppb_read(clockid_t clkid)
{
	double f = 0.0;
	struct timex tx;
	memset(&tx, 0, sizeof(tx));
	if (clock_adjtime(clkid, &tx) < 0)
		pr_err("failed to read out the clock frequency adjustment: %m");
	else
		f = tx.freq / 65.536;
	return f;
}

static void clock_step(clockid_t clkid, int64_t ns)
{
	struct timex tx;
	int sign = 1;
	if (ns < 0) {
		sign = -1;
		ns *= -1;
	}
	memset(&tx, 0, sizeof(tx));
	tx.modes = ADJ_SETOFFSET | ADJ_NANO;
	tx.time.tv_sec  = sign * (ns / NS_PER_SEC);
	tx.time.tv_usec = sign * (ns % NS_PER_SEC);
	/*
	 * The value of a timeval is the sum of its fields, but the
	 * field tv_usec must always be non-negative.
	 */
	if (tx.time.tv_usec < 0) {
		tx.time.tv_sec  -= 1;
		tx.time.tv_usec += 1000000000;
	}
	if (clock_adjtime(clkid, &tx) < 0)
		pr_err("failed to step clock: %m");
}

static void clock_update_grandmaster(struct clock *c)
{
	struct parentDS *pds = &c->dad.pds;
	memset(&c->cur, 0, sizeof(c->cur));
	memset(c->ptl, 0, sizeof(c->ptl));
	pds->parentPortIdentity.clockIdentity   = c->dds.clockIdentity;
	pds->parentPortIdentity.portNumber      = 0;
	pds->grandmasterIdentity                = c->dds.clockIdentity;
	pds->grandmasterClockQuality            = c->dds.clockQuality;
	pds->grandmasterPriority1               = c->dds.priority1;
	pds->grandmasterPriority2               = c->dds.priority2;
	c->dad.path_length                      = 0;
	c->tds.currentUtcOffset                 = CURRENT_UTC_OFFSET;
	if (c->utc_timescale) {
		c->tds.flags = 0;
	} else {
		c->tds.flags = PTP_TIMESCALE;
	}
	c->tds.timeSource                       = INTERNAL_OSCILLATOR;
}

static void clock_update_slave(struct clock *c)
{
	struct parentDS *pds = &c->dad.pds;
	struct ptp_message *msg        = TAILQ_FIRST(&c->best->messages);
	c->cur.stepsRemoved            = 1 + c->best->dataset.stepsRemoved;
	pds->parentPortIdentity        = c->best->dataset.sender;
	pds->grandmasterIdentity       = msg->announce.grandmasterIdentity;
	pds->grandmasterClockQuality   = msg->announce.grandmasterClockQuality;
	pds->grandmasterPriority1      = msg->announce.grandmasterPriority1;
	pds->grandmasterPriority2      = msg->announce.grandmasterPriority2;
	c->tds.currentUtcOffset        = msg->announce.currentUtcOffset;
	c->tds.flags                   = msg->header.flagField[1];
	c->tds.timeSource              = msg->announce.timeSource;
	if (!(c->tds.flags & PTP_TIMESCALE)) {
		pr_warning("foreign master not using PTP timescale");
	}
	if (c->tds.currentUtcOffset < CURRENT_UTC_OFFSET) {
		pr_warning("running in a temporal vortex");
	}
}

static void clock_utc_correct(struct clock *c)
{
	struct timespec offset;
	if (!c->utc_timescale)
		return;
	if (!(c->tds.flags & PTP_TIMESCALE))
		return;
	if (c->tds.flags & UTC_OFF_VALID && c->tds.flags & TIME_TRACEABLE) {
		offset.tv_sec = c->tds.currentUtcOffset;
	} else if (c->tds.currentUtcOffset > CURRENT_UTC_OFFSET) {
		offset.tv_sec = c->tds.currentUtcOffset;
	} else {
		offset.tv_sec = CURRENT_UTC_OFFSET;
	}
	offset.tv_nsec = 0;
	/* Local clock is UTC, but master is TAI. */
	c->master_offset = tmv_add(c->master_offset, timespec_to_tmv(offset));
}

static int forwarding(struct clock *c, struct port *p)
{
	enum port_state ps = port_state(p);
	switch (ps) {
	case PS_MASTER:
	case PS_GRAND_MASTER:
	case PS_SLAVE:
	case PS_UNCALIBRATED:
	case PS_PRE_MASTER:
		return 1;
	default:
		break;
	}
	if (p == c->port[c->nports]) { /*uds*/
		return 1;
	}
	return 0;
}

/* public methods */

UInteger8 clock_class(struct clock *c)
{
	return c->dds.clockQuality.clockClass;
}

struct clock *clock_create(int phc_index, struct interface *iface, int count,
			   enum timestamp_type timestamping, struct default_ds *dds,
			   enum servo_type servo)
{
	int i, fadj = 0, max_adj = 0.0, sw_ts = timestamping == TS_SOFTWARE ? 1 : 0;
	struct clock *c = &the_clock;
	char phc[32];
	struct interface udsif;

	memset(&udsif, 0, sizeof(udsif));
	snprintf(udsif.name, sizeof(udsif.name), UDS_PATH);
	udsif.transport = TRANS_UDS;

	srandom(time(NULL));

	if (c->nports)
		clock_destroy(c);

	c->free_running = dds->free_running;
	c->freq_est_interval = dds->freq_est_interval;
	c->desc = dds->clock_desc;

	if (c->free_running) {
		c->clkid = CLOCK_INVALID;
	} else if (phc_index >= 0) {
		snprintf(phc, 31, "/dev/ptp%d", phc_index);
		c->clkid = phc_open(phc);
		if (c->clkid == CLOCK_INVALID) {
			pr_err("Failed to open %s: %m", phc);
			return NULL;
		}
		max_adj = phc_max_adj(c->clkid);
		if (!max_adj) {
			pr_err("clock is not adjustable");
			return NULL;
		}
	} else {
		c->clkid = CLOCK_REALTIME;
		c->utc_timescale = 1;
		max_adj = 512000;
	}

	if (c->clkid != CLOCK_INVALID) {
		fadj = (int) clock_ppb_read(c->clkid);
	}
	c->servo = servo_create(servo, -fadj, max_adj, sw_ts);
	if (!c->servo) {
		pr_err("Failed to create clock servo");
		return NULL;
	}
	c->avg_delay = mave_create(MAVE_LENGTH);
	if (!c->avg_delay) {
		pr_err("Failed to create moving average");
		return NULL;
	}

	c->dds = dds->dds;

	/* Initialize the parentDS. */
	clock_update_grandmaster(c);
	c->dad.pds.parentStats                           = 0;
	c->dad.pds.observedParentOffsetScaledLogVariance = 0xffff;
	c->dad.pds.observedParentClockPhaseChangeRate    = 0x7fffffff;
	c->dad.ptl = c->ptl;

	for (i = 0; i < ARRAY_SIZE(c->pollfd); i++) {
		c->pollfd[i].fd = -1;
		c->pollfd[i].events = 0;
	}

	clock_sync_interval(c, 0);

	for (i = 0; i < count; i++) {
		c->fault_timeout[i] = iface[i].pod.fault_reset_interval;
		c->port[i] = port_open(phc_index, timestamping, 1+i, &iface[i], c);
		if (!c->port[i]) {
			pr_err("failed to open port %s", iface[i].name);
			return NULL;
		}
		c->fault_fd[i] = timerfd_create(CLOCK_MONOTONIC, 0);
		if (c->fault_fd[i] < 0) {
			pr_err("timerfd_create failed: %m");
			return NULL;
		}
		c->pollfd[N_CLOCK_PFD * i + N_POLLFD].fd = c->fault_fd[i];
		c->pollfd[N_CLOCK_PFD * i + N_POLLFD].events = POLLIN|POLLPRI;
	}

	/*
	 * One extra port is for the UDS interface.
	 */
	c->port[i] = port_open(phc_index, timestamping, 0, &udsif, c);
	if (!c->port[i]) {
		pr_err("failed to open the UDS port");
		return NULL;
	}

	c->dds.numberPorts = c->nports = count;

	for (i = 0; i < c->nports; i++)
		port_dispatch(c->port[i], EV_INITIALIZE, 0);

	port_dispatch(c->port[i], EV_INITIALIZE, 0); /*uds*/

	return c;
}

struct dataset *clock_best_foreign(struct clock *c)
{
	return c->best ? &c->best->dataset : NULL;
}

struct port *clock_best_port(struct clock *c)
{
	return c->best ? c->best->port : NULL;
}

struct dataset *clock_default_ds(struct clock *c)
{
	struct dataset *out = &c->default_dataset;
	struct defaultDS *in = &c->dds;

	out->priority1              = in->priority1;
	out->identity               = in->clockIdentity;
	out->quality                = in->clockQuality;
	out->priority2              = in->priority2;
	out->stepsRemoved           = 0;
	out->sender.clockIdentity   = in->clockIdentity;
	out->sender.portNumber      = 0;
	out->receiver.clockIdentity = in->clockIdentity;
	out->receiver.portNumber    = 0;

	return out;
}

UInteger8 clock_domain_number(struct clock *c)
{
	return c->dds.domainNumber;
}

void clock_follow_up_info(struct clock *c, struct follow_up_info_tlv *f)
{
	c->status.cumulativeScaledRateOffset = f->cumulativeScaledRateOffset;
	c->status.scaledLastGmPhaseChange = f->scaledLastGmPhaseChange;
	c->status.gmTimeBaseIndicator = f->gmTimeBaseIndicator;
	memcpy(&c->status.lastGmPhaseChange, &f->lastGmPhaseChange,
	       sizeof(c->status.lastGmPhaseChange));
}

struct ClockIdentity clock_identity(struct clock *c)
{
	return c->dds.clockIdentity;
}

void clock_install_fda(struct clock *c, struct port *p, struct fdarray fda)
{
	int i, j, k;
	for (i = 0; i < c->nports + 1; i++) {
		if (p == c->port[i])
			break;
	}
	for (j = 0; j < N_POLLFD; j++) {
		k = N_CLOCK_PFD * i + j;
		c->pollfd[k].fd = fda.fd[j];
		c->pollfd[k].events = POLLIN|POLLPRI;
	}
}

static void clock_forward_mgmt_msg(struct clock *c, struct port *p, struct ptp_message *msg)
{
	int i, pdulen, msg_ready = 0;
	struct port *fwd;
	if (forwarding(c, p) && msg->management.boundaryHops) {
		for (i = 0; i < c->nports + 1; i++) {
			fwd = c->port[i];
			if (fwd != p && forwarding(c, fwd)) {
				/* delay calling msg_pre_send until
				 * actually forwarding */
				if (!msg_ready) {
					msg_ready = 1;
					pdulen = msg->header.messageLength;
					msg->management.boundaryHops--;
					msg_pre_send(msg);
				}
				if (port_forward(fwd, msg, pdulen))
					pr_err("port %d: management forward failed", i);
			}
		}
		if (msg_ready) {
			msg_post_recv(msg, pdulen);
			msg->management.boundaryHops++;
		}
	}
}

void clock_manage(struct clock *c, struct port *p, struct ptp_message *msg)
{
	int i;
	struct management_tlv *mgt;
	struct ClockIdentity *tcid, wildcard = {
		{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
	};

	/* Forward this message out all eligible ports. */
	clock_forward_mgmt_msg(c, p, msg);

	/* Apply this message to the local clock and ports. */
	tcid = &msg->management.targetPortIdentity.clockIdentity;
	if (!cid_eq(tcid, &wildcard) && !cid_eq(tcid, &c->dds.clockIdentity)) {
		return;
	}
	if (msg->tlv_count != 1) {
		return;
	}
	mgt = (struct management_tlv *) msg->management.suffix;

	/*
	  The correct length according to the management ID is checked
	  in tlv.c, but management TLVs with empty bodies are also
	  received successfully to support GETs and CMDs. At this
	  point the TLV either has the correct length or length 2.
	*/
	switch (management_action(msg)) {
	case GET:
		if (mgt->length != 2) {
			clock_management_send_error(p, msg, WRONG_LENGTH);
			return;
		}
		if (clock_management_get_response(c, p, mgt->id, msg))
			return;
		break;
	case SET:
		if (mgt->length == 2 && mgt->id != NULL_MANAGEMENT) {
			clock_management_send_error(p, msg, WRONG_LENGTH);
			return;
		}
		if (clock_management_set(c, p, mgt->id, msg))
			return;
		break;
	case COMMAND:
		if (mgt->length != 2) {
			clock_management_send_error(p, msg, WRONG_LENGTH);
			return;
		}
		break;
	default:
		return;
	}

	switch (mgt->id) {
	case USER_DESCRIPTION:
	case SAVE_IN_NON_VOLATILE_STORAGE:
	case RESET_NON_VOLATILE_STORAGE:
	case INITIALIZE:
	case FAULT_LOG:
	case FAULT_LOG_RESET:
	case DEFAULT_DATA_SET:
	case CURRENT_DATA_SET:
	case PARENT_DATA_SET:
	case TIME_PROPERTIES_DATA_SET:
	case PRIORITY1:
	case PRIORITY2:
	case DOMAIN:
	case SLAVE_ONLY:
	case TIME:
	case CLOCK_ACCURACY:
	case UTC_PROPERTIES:
	case TRACEABILITY_PROPERTIES:
	case TIMESCALE_PROPERTIES:
	case PATH_TRACE_LIST:
	case PATH_TRACE_ENABLE:
	case GRANDMASTER_CLUSTER_TABLE:
	case ACCEPTABLE_MASTER_TABLE:
	case ACCEPTABLE_MASTER_MAX_TABLE_SIZE:
	case ALTERNATE_TIME_OFFSET_ENABLE:
	case ALTERNATE_TIME_OFFSET_NAME:
	case ALTERNATE_TIME_OFFSET_MAX_KEY:
	case ALTERNATE_TIME_OFFSET_PROPERTIES:
	case TRANSPARENT_CLOCK_DEFAULT_DATA_SET:
	case PRIMARY_DOMAIN:
	case TIME_STATUS_NP:
		clock_management_send_error(p, msg, NOT_SUPPORTED);
		break;
	default:
		for (i = 0; i < c->nports; i++) {
			if (port_manage(c->port[i], p, msg))
				break;
		}
		break;
	}
}

struct parent_ds *clock_parent_ds(struct clock *c)
{
	return &c->dad;
}

struct PortIdentity clock_parent_identity(struct clock *c)
{
	return c->dad.pds.parentPortIdentity;
}

int clock_poll(struct clock *c)
{
	int cnt, err, i, j, k, lost = 0, sde = 0;
	enum fsm_event event;

	cnt = poll(c->pollfd, ARRAY_SIZE(c->pollfd), -1);
	if (cnt < 0) {
		if (EINTR == errno) {
			return 0;
		} else {
			pr_emerg("poll failed");
			return -1;
		}
	} else if (!cnt) {
		return 0;
	}

	for (i = 0; i < c->nports; i++) {

		/* Let the ports handle their events. */
		for (j = err = 0; j < N_POLLFD && !err; j++) {
			k = N_CLOCK_PFD * i + j;
			if (c->pollfd[k].revents & (POLLIN|POLLPRI)) {
				event = port_event(c->port[i], j);
				if (EV_STATE_DECISION_EVENT == event)
					sde = 1;
				if (EV_ANNOUNCE_RECEIPT_TIMEOUT_EXPIRES == event)
					lost = 1;
				err = port_dispatch(c->port[i], event, 0);
				/* Clear any fault after a little while. */
				if (PS_FAULTY == port_state(c->port[i])) {
					clock_fault_timeout(c, i, 1);
					break;
				}
			}
		}

		/* Check the fault timer. */
		k = N_CLOCK_PFD * i + N_POLLFD;
		if (c->pollfd[k].revents & (POLLIN|POLLPRI)) {
			clock_fault_timeout(c, i, 0);
			port_dispatch(c->port[i], EV_FAULT_CLEARED, 0);
		}
	}

	/* Check the UDS port. */
	for (j = 0; j < N_POLLFD; j++) {
		k = N_CLOCK_PFD * i + j;
		if (c->pollfd[k].revents & (POLLIN|POLLPRI)) {
			event = port_event(c->port[i], j);
		}
	}

	if (lost && clock_master_lost(c))
		clock_update_grandmaster(c);
	if (sde)
		handle_state_decision_event(c);

	return 0;
}

void clock_path_delay(struct clock *c, struct timespec req, struct timestamp rx,
		      Integer64 correction)
{
	tmv_t c1, c2, c3, pd, t1, t2, t3, t4;

	if (tmv_is_zero(c->t1))
		return;

	c1 = c->c1;
	c2 = c->c2;
	c3 = correction_to_tmv(correction);
	t1 = c->t1;
	t2 = c->t2;
	t3 = timespec_to_tmv(req);
	t4 = timestamp_to_tmv(rx);

	/*
	 * c->path_delay = (t2 - t3) + (t4 - t1);
	 * c->path_delay -= c_sync + c_fup + c_delay_resp;
	 * c->path_delay /= 2.0;
	 */
	pd = tmv_add(tmv_sub(t2, t3), tmv_sub(t4, t1));
	pd = tmv_sub(pd, tmv_add(c1, tmv_add(c2, c3)));
	pd = tmv_div(pd, 2);

	if (pd < 0) {
		pr_warning("negative path delay %10lld", pd);
		pr_warning("path_delay = (t2 - t3) + (t4 - t1)");
		pr_warning("t2 - t3 = %+10lld", t2 - t3);
		pr_warning("t4 - t1 = %+10lld", t4 - t1);
		pr_warning("c1 %10lld", c1);
		pr_warning("c2 %10lld", c2);
		pr_warning("c3 %10lld", c3);
	}

	c->path_delay = mave_accumulate(c->avg_delay, pd);

	c->cur.meanPathDelay = tmv_to_TimeInterval(c->path_delay);

	pr_debug("path delay    %10lld %10lld", c->path_delay, pd);
}

void clock_peer_delay(struct clock *c, tmv_t ppd, double nrr)
{
	c->path_delay = ppd;
	c->nrr = nrr;
}

void clock_remove_fda(struct clock *c, struct port *p, struct fdarray fda)
{
	int i, j, k;
	for (i = 0; i < c->nports + 1; i++) {
		if (p == c->port[i])
			break;
	}
	for (j = 0; j < N_POLLFD; j++) {
		k = N_CLOCK_PFD * i + j;
		c->pollfd[k].fd = -1;
		c->pollfd[k].events = 0;
	}
}

int clock_slave_only(struct clock *c)
{
	return c->dds.flags & DDS_SLAVE_ONLY;
}

UInteger16 clock_steps_removed(struct clock *c)
{
	return c->cur.stepsRemoved;
}

enum servo_state clock_synchronize(struct clock *c,
				   struct timespec ingress_ts,
				   struct timestamp origin_ts,
				   Integer64 correction1,
				   Integer64 correction2)
{
	double adj;
	tmv_t ingress, origin;
	enum servo_state state = SERVO_UNLOCKED;

	ingress = timespec_to_tmv(ingress_ts);
	origin  = timestamp_to_tmv(origin_ts);

	c->t1 = origin;
	c->t2 = ingress;

	c->c1 = correction_to_tmv(correction1);
	c->c2 = correction_to_tmv(correction2);

	/*
	 * c->master_offset = ingress - origin - c->path_delay - c->c1 - c->c2;
	 */
	c->master_offset = tmv_sub(ingress,
		tmv_add(origin, tmv_add(c->path_delay, tmv_add(c->c1, c->c2))));

	clock_utc_correct(c);

	c->cur.offsetFromMaster = tmv_to_TimeInterval(c->master_offset);

	if (!c->path_delay)
		return state;

	if (c->free_running)
		return clock_no_adjust(c);

	adj = servo_sample(c->servo, c->master_offset, ingress, &state);

	pr_info("master offset %10" PRId64 " s%d freq %+7.0f "
		"path delay %9" PRId64,
		c->master_offset, state, adj, c->path_delay);

	switch (state) {
	case SERVO_UNLOCKED:
		break;
	case SERVO_JUMP:
		clock_ppb(c->clkid, -adj);
		clock_step(c->clkid, -c->master_offset);
		c->t1 = tmv_zero();
		c->t2 = tmv_zero();
		break;
	case SERVO_LOCKED:
		clock_ppb(c->clkid, -adj);
		break;
	}
	return state;
}

void clock_sync_interval(struct clock *c, int n)
{
	int shift = c->freq_est_interval - n;

	if (shift < 0)
		shift = 0;

	c->fest.max_count = (1 << shift);
}

struct timePropertiesDS *clock_time_properties(struct clock *c)
{
	return &c->tds;
}

static void handle_state_decision_event(struct clock *c)
{
	struct foreign_clock *best = NULL, *fc;
	int fresh_best = 0, i;

	for (i = 0; i < c->nports; i++) {
		fc = port_compute_best(c->port[i]);
		if (!fc)
			continue;
		if (!best || dscmp(&fc->dataset, &best->dataset) > 0)
			best = fc;
	}

	if (!best)
		return;

	pr_notice("selected best master clock %s",
		cid2str(&best->dataset.identity));

	if (!cid_eq(&best->dataset.identity, &c->best_id)) {
		clock_freq_est_reset(c);
		mave_reset(c->avg_delay);
		fresh_best = 1;
	}

	c->best = best;
	c->best_id = best->dataset.identity;

	for (i = 0; i < c->nports; i++) {
		enum port_state ps;
		enum fsm_event event;
		ps = bmc_state_decision(c, c->port[i]);
		switch (ps) {
		case PS_LISTENING:
			event = EV_NONE;
			break;
		case PS_GRAND_MASTER:
			clock_update_grandmaster(c);
			event = EV_RS_GRAND_MASTER;
			break;
		case PS_MASTER:
			event = EV_RS_MASTER;
			break;
		case PS_PASSIVE:
			event = EV_RS_PASSIVE;
			break;
		case PS_SLAVE:
			clock_update_slave(c);
			event = EV_RS_SLAVE;
			break;
		default:
			event = EV_FAULT_DETECTED;
			break;
		}
		port_dispatch(c->port[i], event, fresh_best);
	}
}

struct clock_description *clock_description(struct clock *c)
{
	return &c->desc;
}