Re: [PATCH v6 3/3] examples/ptpclient: add frequency adjustment

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 10/11/2024 7:34 AM, Mingjin Ye wrote:
> This patch adds PI servo controller to support frequency
> adjustment API for IEEE1588 PTP.
> 
> For example, the command for starting ptpclient with PI controller is:
> dpdk-ptpclient -a 0000:81:00.0 -c 1 -n 3 -- -T 0 -p 0x1 -c 1
> 
> Signed-off-by: Simei Su <simei.su@intel.com>
> Signed-off-by: Wenjun Wu <wenjun1.wu@intel.com>
> Signed-off-by: Mingjin Ye <mingjinx.ye@intel.com>
> ---
>  doc/guides/sample_app_ug/ptpclient.rst |  12 +-
>  examples/ptpclient/ptpclient.c         | 284 +++++++++++++++++++++++--
>  2 files changed, 274 insertions(+), 22 deletions(-)
> 
> diff --git a/doc/guides/sample_app_ug/ptpclient.rst b/doc/guides/sample_app_ug/ptpclient.rst
> index d47e942738..89fe575b5f 100644
> --- a/doc/guides/sample_app_ug/ptpclient.rst
> +++ b/doc/guides/sample_app_ug/ptpclient.rst
> @@ -50,6 +50,10 @@ The adjustment for slave can be represented as:
>  If the command line parameter ``-T 1`` is used the application also
>  synchronizes the PTP PHC clock with the Linux kernel clock.
>  
> +If the command line parameter ``-c 1`` is used, the application will also
> +use the servo of the local clock. Only one type of servo is currently
> +implemented, the PI controller. Default 0 (not used).
> +
>  Compiling the Application
>  -------------------------
>  
> @@ -65,7 +69,7 @@ To run the example in a ``linux`` environment:
>  
>  .. code-block:: console
>  
> -    ./<build_dir>/examples/dpdk-ptpclient -l 1 -n 4 -- -p 0x1 -T 0
> +    ./<build_dir>/examples/dpdk-ptpclient -l 1 -n 4 -- -p 0x1 -T 0 -c 1
>  
>  Refer to *DPDK Getting Started Guide* for general information on running
>  applications and the Environment Abstraction Layer (EAL) options.
> @@ -73,7 +77,13 @@ applications and the Environment Abstraction Layer (EAL) options.
>  * ``-p portmask``: Hexadecimal portmask.
>  * ``-T 0``: Update only the PTP slave clock.
>  * ``-T 1``: Update the PTP slave clock and synchronize the Linux Kernel to the PTP clock.
> +* ``-c 0``: Not used clock servo controller.
> +* ``-c 1``: The clock servo PI controller is used and the log will print information
> +            about "master offset".
>  
> +Also, by adding ``-T 1`` and ``-c 1`` , the ``master offset`` value printed in the
> +log will slowly converge and eventually stabilise at the nanosecond level. The
> +synchronisation accuracy is much higher compared to not using a servo controller.
>  

What is this new feature / argument dependency to the new
'rte_eth_timesync_adjust_freq()' API?

Right now only one PMD supports it, should application check the support
of the API when -c parameter provided, and fail it if is not supported?


>  Code Explanation
>  ----------------
> diff --git a/examples/ptpclient/ptpclient.c b/examples/ptpclient/ptpclient.c
> index afb61bba51..dea8d9d54a 100644
> --- a/examples/ptpclient/ptpclient.c
> +++ b/examples/ptpclient/ptpclient.c
> @@ -46,6 +46,35 @@ static volatile bool force_quit;
>  #define KERNEL_TIME_ADJUST_LIMIT  20000
>  #define PTP_PROTOCOL             0x88F7
>  
> +#define KP 0.7
> +#define KI 0.3
> +#define FREQ_EST_MARGIN 0.001
> +
> +enum servo_state {
> +	SERVO_UNLOCKED,
> +	SERVO_JUMP,
> +	SERVO_LOCKED,
> +};
> +
> +struct pi_servo {
> +	double offset[2];
> +	double local[2];
> +	double drift;
> +	double last_freq;
> +	int count;
> +
> +	double max_frequency;
> +	double step_threshold;
> +	double first_step_threshold;
> +	int first_update;
> +};
> +
> +enum controller_mode {
> +	MODE_NONE,
> +	MODE_PI,
> +	MAX_ALL
> +} mode = MODE_NONE;
> +
>  struct rte_mempool *mbuf_pool;
>  uint32_t ptp_enabled_port_mask;
>  uint8_t ptp_enabled_port_nb;
> @@ -135,6 +164,9 @@ struct ptpv2_data_slave_ordinary {
>  	uint8_t ptpset;
>  	uint8_t kernel_time_set;
>  	uint16_t current_ptp_port;
> +	int64_t master_offset;
> +	int64_t path_delay;
> +	struct pi_servo *servo;
>  };
>  
>  static struct ptpv2_data_slave_ordinary ptp_data;
> @@ -293,36 +325,44 @@ print_clock_info(struct ptpv2_data_slave_ordinary *ptp_data)
>  			ptp_data->tstamp3.tv_sec,
>  			(ptp_data->tstamp3.tv_nsec));
>  
> -	printf("\nT4 - Master Clock.  %lds %ldns ",
> +	printf("\nT4 - Master Clock.  %lds %ldns\n",
>  			ptp_data->tstamp4.tv_sec,
>  			(ptp_data->tstamp4.tv_nsec));
>  
> -	printf("\nDelta between master and slave clocks:%"PRId64"ns\n",
> +	if (mode == MODE_NONE) {
> +		printf("\nDelta between master and slave clocks:%"PRId64"ns\n",
>  			ptp_data->delta);
>  
> -	clock_gettime(CLOCK_REALTIME, &sys_time);
> -	rte_eth_timesync_read_time(ptp_data->current_ptp_port, &net_time);
> +		clock_gettime(CLOCK_REALTIME, &sys_time);
> +		rte_eth_timesync_read_time(ptp_data->current_ptp_port,
> +					   &net_time);
>  
> -	time_t ts = net_time.tv_sec;
> +		time_t ts = net_time.tv_sec;
>  
> -	printf("\n\nComparison between Linux kernel Time and PTP:");
> +		printf("\n\nComparison between Linux kernel Time and PTP:");
>  
> -	printf("\nCurrent PTP Time: %.24s %.9ld ns",
> +		printf("\nCurrent PTP Time: %.24s %.9ld ns",
>  			ctime(&ts), net_time.tv_nsec);
>  
> -	nsec = (int64_t)timespec64_to_ns(&net_time) -
> +		nsec = (int64_t)timespec64_to_ns(&net_time) -
>  			(int64_t)timespec64_to_ns(&sys_time);
> -	ptp_data->new_adj = ns_to_timeval(nsec);
> +		ptp_data->new_adj = ns_to_timeval(nsec);
>  
> -	gettimeofday(&ptp_data->new_adj, NULL);
> +		gettimeofday(&ptp_data->new_adj, NULL);
>  
> -	time_t tp = ptp_data->new_adj.tv_sec;
> +		time_t tp = ptp_data->new_adj.tv_sec;
>  
> -	printf("\nCurrent SYS Time: %.24s %.6ld ns",
> -				ctime(&tp), ptp_data->new_adj.tv_usec);
> +		printf("\nCurrent SYS Time: %.24s %.6ld ns",
> +			ctime(&tp), ptp_data->new_adj.tv_usec);
>  
> -	printf("\nDelta between PTP and Linux Kernel time:%"PRId64"ns\n",
> -				nsec);
> +		printf("\nDelta between PTP and Linux Kernel time:%"PRId64"ns\n",
> +			nsec);
> +	}
> +
> +	if (mode == MODE_PI) {
> +		printf("path delay: %"PRId64"ns\n", ptp_data->path_delay);
> +		printf("master offset: %"PRId64"ns\n", ptp_data->master_offset);
> +	}
>  
>  	printf("[Ctrl+C to quit]\n");
>  
> @@ -529,6 +569,149 @@ update_kernel_time(void)
>  
>  }
>  
> +static void
> +clock_path_delay(struct ptpv2_data_slave_ordinary *ptp_data)
> +{
> +	uint64_t t1_ns, t2_ns, t3_ns, t4_ns;
> +	int64_t pd, diff;
> +
> +	t1_ns = timespec64_to_ns(&ptp_data->tstamp1);
> +	t2_ns = timespec64_to_ns(&ptp_data->tstamp2);
> +	t3_ns = timespec64_to_ns(&ptp_data->tstamp3);
> +	t4_ns = timespec64_to_ns(&ptp_data->tstamp4);
> +
> +	pd = (t2_ns - t3_ns) + (t4_ns - t1_ns);
> +	diff = t3_ns - t2_ns;
> +	if (diff <= INT32_MAX && diff >= INT32_MIN)
> +		ptp_data->path_delay = pd / 2;
> +	else
> +		ptp_data->path_delay = 0;
> +}
> +
> +static double
> +pi_sample(struct pi_servo *s, int64_t offset, double local_ts,
> +	  enum servo_state *state)
> +{
> +	double ki_term, ppb = s->last_freq;
> +	double freq_est_interval, localdiff;
> +
> +	switch (s->count) {
> +	case 0:
> +		s->offset[0] = offset;
> +		s->local[0] = local_ts;
> +		*state = SERVO_UNLOCKED;
> +		s->count = 1;
> +		break;
> +	case 1:
> +		s->offset[1] = offset;
> +		s->local[1] = local_ts;
> +
> +		/* Make sure the first sample is older than the second. */
> +		if (s->local[0] >= s->local[1]) {
> +			*state = SERVO_UNLOCKED;
> +			s->count = 0;
> +			break;
> +		}
> +
> +		/* Wait long enough before estimating the frequency offset. */
> +		localdiff = (s->local[1] - s->local[0]) / 1e9;
> +		localdiff += localdiff * FREQ_EST_MARGIN;
> +		freq_est_interval = 0.016 / KI;
> +		if (freq_est_interval > 1000.0)
> +			freq_est_interval = 1000.0;
> +
> +		if (localdiff < freq_est_interval) {
> +			*state = SERVO_UNLOCKED;
> +			break;
> +		}
> +
> +		/* Adjust drift by the measured frequency offset. */
> +		s->drift += (1e9 - s->drift) * (s->offset[1] - s->offset[0]) /
> +						(s->local[1] - s->local[0]);
> +
> +		if (s->drift < -s->max_frequency)
> +			s->drift = -s->max_frequency;
> +		else if (s->drift > s->max_frequency)
> +			s->drift = s->max_frequency;
> +
> +		if ((s->first_update &&
> +		     s->first_step_threshold &&
> +		     s->first_step_threshold < llabs(offset)) ||
> +		    (s->step_threshold &&
> +		     s->step_threshold < llabs(offset)))
> +			*state = SERVO_JUMP;
> +		else
> +			*state = SERVO_LOCKED;
> +
> +		ppb = s->drift;
> +		s->count = 2;
> +		break;
> +	case 2:
> +		/*
> +		 * reset the clock servo when offset is greater than the max
> +		 * offset value. Note that the clock jump will be performed in
> +		 * step 1, so it is not necessary to have clock jump
> +		 * immediately. This allows re-calculating drift as in initial
> +		 * clock startup.
> +		 */
> +		if (s->step_threshold &&
> +		    s->step_threshold < llabs(offset)) {
> +			*state = SERVO_UNLOCKED;
> +			s->count = 0;
> +			break;
> +		}
> +
> +		ki_term = KI * offset;
> +		ppb = KP * offset + s->drift + ki_term;
> +		if (ppb < -s->max_frequency)
> +			ppb = -s->max_frequency;
> +		else if (ppb > s->max_frequency)
> +			ppb = s->max_frequency;
> +		else
> +			s->drift += ki_term;
> +
> +		*state = SERVO_LOCKED;
> +		break;
> +	}
> +
> +	s->last_freq = ppb;
> +	return ppb;
> +}
> +
> +static void
> +ptp_adjust_servo(struct ptpv2_data_slave_ordinary *ptp_data)
> +{
> +	uint64_t t1_ns, t2_ns;
> +	double adj_freq;
> +	enum servo_state state = SERVO_UNLOCKED;
> +
> +	t1_ns = timespec64_to_ns(&ptp_data->tstamp1);
> +	t2_ns = timespec64_to_ns(&ptp_data->tstamp2);
> +	ptp_data->master_offset = t2_ns - t1_ns - ptp_data->path_delay;
> +	if (!ptp_data->path_delay)
> +		return;
> +
> +	adj_freq = pi_sample(ptp_data->servo, ptp_data->master_offset, t2_ns,
> +		     &state);
> +
> +	switch (state) {
> +	case SERVO_UNLOCKED:
> +		break;
> +	case SERVO_JUMP:
> +		ptp_data->servo->first_update = 0;
> +		rte_eth_timesync_adjust_freq(ptp_data->portid,
> +						-(long)(adj_freq * 65.536));
> +		rte_eth_timesync_adjust_time(ptp_data->portid,
> +					     -ptp_data->master_offset);
> +		break;
> +	case SERVO_LOCKED:
> +		ptp_data->servo->first_update = 0;
> +		rte_eth_timesync_adjust_freq(ptp_data->portid,
> +					     -(long)(adj_freq * 65.536));
> +		break;
> +	}
> +}
> +
>  /*
>   * Parse the DELAY_RESP message.
>   */
> @@ -553,11 +736,16 @@ parse_drsp(struct ptpv2_data_slave_ordinary *ptp_data)
>  				((uint64_t)ntohl(rx_tstamp->sec_lsb)) |
>  				(((uint64_t)ntohs(rx_tstamp->sec_msb)) << 32);
>  
> -			/* Evaluate the delta for adjustment. */
> -			ptp_data->delta = delta_eval(ptp_data);
> +			if (mode == MODE_PI) {
> +				clock_path_delay(ptp_data);
> +				ptp_adjust_servo(ptp_data);
> +			} else {
> +				/* Evaluate the delta for adjustment. */
> +				ptp_data->delta = delta_eval(ptp_data);
>  
> -			rte_eth_timesync_adjust_time(ptp_data->portid,
> -						     ptp_data->delta);
> +				rte_eth_timesync_adjust_time(ptp_data->portid,
> +								ptp_data->delta);
> +			}
>  
>  			ptp_data->current_ptp_port = ptp_data->portid;
>  
> @@ -652,7 +840,9 @@ print_usage(const char *prgname)
>  	printf("%s [EAL options] -- -p PORTMASK -T VALUE\n"
>  		" -T VALUE: 0 - Disable, 1 - Enable Linux Clock"
>  		" Synchronization (0 default)\n"
> -		" -p PORTMASK: hexadecimal bitmask of ports to configure\n",
> +		" -p PORTMASK: hexadecimal bitmask of ports to configure\n"
> +		" -c CONTROLLER: 0 - Not used, 1 - PI. The servo which is"
> +		" used to synchronize the local clock. (0 default)\n",
>  		prgname);
>  }
>  
> @@ -688,6 +878,36 @@ parse_ptp_kernel(const char *param)
>  	return 1;
>  }
>  
> +static int
> +parse_ptp_servo_mode(const char *param)
> +{
> +	char *end = NULL;
> +	unsigned long pm;
> +
> +	/* Parse the hexadecimal string. */
> +	pm = strtoul(param, &end, 10);
> +
> +	if ((param[0] == '\0') || (end == NULL) || (*end != '\0'))
> +		return -1;
> +
> +	return pm;
> +}
> +
> +static void
> +servo_init(struct pi_servo *servo)
> +{
> +	memset(servo, 0x00, sizeof(*servo));
> +
> +	servo->drift = 100000000;
> +	servo->last_freq = 100000000;
> +	servo->count = 0;
> +
> +	servo->max_frequency = 100000000;
> +	servo->step_threshold = 0.1 * NSEC_PER_SEC;
> +	servo->first_step_threshold = 0.00002 * NSEC_PER_SEC;
> +	servo->first_update = 1;
> +}
> +
>  /* Parse the commandline arguments. */
>  static int
>  ptp_parse_args(int argc, char **argv)
> @@ -700,7 +920,7 @@ ptp_parse_args(int argc, char **argv)
>  
>  	argvopt = argv;
>  
> -	while ((opt = getopt_long(argc, argvopt, "p:T:",
> +	while ((opt = getopt_long(argc, argvopt, "p:T:c:",
>  				  lgopts, &option_index)) != EOF) {
>  
>  		switch (opt) {
> @@ -724,6 +944,17 @@ ptp_parse_args(int argc, char **argv)
>  
>  			ptp_data.kernel_time_set = ret;
>  			break;
> +		case 'c':
> +			ret = parse_ptp_servo_mode(optarg);
> +			if (ret == 0) {
> +				mode = MODE_NONE;
> +			} else if (ret == 1) {
> +				mode = MODE_PI;
> +			} else {
> +				print_usage(prgname);
> +				return -1;
> +			}
> +			break;
>  
>  		default:
>  			print_usage(prgname);
> @@ -778,6 +1009,14 @@ main(int argc, char *argv[])
>  		rte_exit(EXIT_FAILURE, "Error with PTP initialization\n");
>  	/* >8 End of parsing specific arguments. */
>  
> +	if (mode == MODE_PI) {
> +		ptp_data.servo = malloc(sizeof(*(ptp_data.servo)));
> +		if (!ptp_data.servo)
> +			rte_exit(EXIT_FAILURE, "no memory for servo\n");
> +
> +		servo_init(ptp_data.servo);
> +	}
> +
>  	/* Check that there is an even number of ports to send/receive on. */
>  	nb_ports = rte_eth_dev_count_avail();
>  
> @@ -831,6 +1070,9 @@ main(int argc, char *argv[])
>  		rte_eth_dev_close(portid);
>  	}
>  
> +	if (mode == MODE_PI)
> +		free(ptp_data.servo);
> +
>  	/* clean up the EAL */
>  	rte_eal_cleanup();
>