The ptpclient example corrected only the instantaneous phase offset by calling rte_eth_timesync_adjust_time() once per DELAY_RESP. It never compensated for oscillator frequency drift, so the master/slave offset settled at a non-zero steady-state value (proportional to the drift rate times the sync interval) instead of converging towards zero.
Replace the one-shot phase step with a PI clock servo, using the same model as linuxptp. The servo output is a frequency correction that is applied through the best mechanism the PMD provides: - When the driver supports hardware frequency adjustment, the correction is applied with rte_eth_timesync_adjust_freq() (for example the E810 INCVAL register). - Otherwise the same correction is realized in software as an incremental phase step over the elapsed interval using rte_eth_timesync_adjust_time(), which every timesync-capable PMD provides. Hardware support is probed once at runtime, so any PMD that implements the adjust_freq operation in the future uses the hardware path without further changes. The selected path is logged once per port. Bugzilla ID: 1474 Signed-off-by: Soumyadeep Hore <[email protected]> --- examples/ptpclient/ptpclient.c | 114 ++++++++++++++++++++++++++++++++- 1 file changed, 111 insertions(+), 3 deletions(-) diff --git a/examples/ptpclient/ptpclient.c b/examples/ptpclient/ptpclient.c index 59ce892742..d3e947941e 100644 --- a/examples/ptpclient/ptpclient.c +++ b/examples/ptpclient/ptpclient.c @@ -34,6 +34,12 @@ static volatile bool force_quit; #define NSEC_PER_SEC 1000000000L #define KERNEL_TIME_ADJUST_LIMIT 20000 +/* PI clock servo parameters (same model as linuxptp). */ +#define PTP_SERVO_KP 0.7 +#define PTP_SERVO_KI 0.3 +/* Step the clock directly when the offset exceeds this threshold. */ +#define PTP_STEP_THRESHOLD_NS 100000 + struct rte_mempool *mbuf_pool; uint32_t ptp_enabled_port_mask; uint8_t ptp_enabled_port_nb; @@ -97,6 +103,18 @@ struct ptpv2_time_receiver_ordinary { static struct ptpv2_time_receiver_ordinary ptp_data; +/* Per-port clock servo state. */ +struct ptp_clock_servo { + int freq_adj_supported; /* -1 unknown, 0 software, 1 hardware */ + int count; /* number of samples processed */ + int64_t last_offset; /* previous offset (ns) */ + uint64_t last_local; /* NIC clock at previous sample (ns) */ + double drift_ppb; /* integral term / standing frequency (ppb) */ +}; + +static struct ptp_clock_servo ptp_servo[RTE_MAX_ETHPORTS]; + + static inline uint64_t timespec64_to_ns(const struct timespec *ts) { return ((uint64_t) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec; @@ -229,7 +247,7 @@ print_clock_info(struct ptpv2_time_receiver_ordinary *ptp) int64_t nsec; struct timespec net_time, sys_time; - printf("time transmitter clock id: %02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x", + printf("\ntime transmitter clock id: %02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x", ptp->transmitter_clock_id[0], ptp->transmitter_clock_id[1], ptp->transmitter_clock_id[2], @@ -308,6 +326,93 @@ delta_eval(struct ptpv2_time_receiver_ordinary *ptp) return delta; } +/* + * Convert a frequency correction in ppb to the scaled ppm (16-bit fractional) + * unit expected by rte_eth_timesync_adjust_freq(). + */ +static int64_t +ppb_to_scaled_ppm(double ppb) +{ + return (int64_t)(ppb * 65536.0 / 1000.0); +} + +/* + * PI clock servo. Drives the master/slave offset to zero by compensating for + * clock frequency drift, not just the instantaneous phase offset. + * + * The servo output is a frequency correction (ppb). When the PMD supports + * hardware frequency adjustment it is applied via rte_eth_timesync_adjust_freq() + * (e.g. the E810 INCVAL register). Otherwise the same correction is realized in + * software as an incremental phase step over the elapsed interval using + * rte_eth_timesync_adjust_time(), which every timesync-capable PMD provides. + */ +static void +clock_servo(struct ptpv2_time_receiver_ordinary *ptp, int64_t offset) +{ + struct ptp_clock_servo *servo = &ptp_servo[ptp->portid]; + struct timespec now; + uint64_t local; + double ppb, ki_term; + + /* Probe hardware frequency adjustment support once. */ + if (servo->freq_adj_supported < 0) { + servo->freq_adj_supported = + (rte_eth_timesync_adjust_freq(ptp->portid, 0) == 0) ? 1 : 0; + printf("Port %u clock frequency adjustment: %s\n", ptp->portid, + servo->freq_adj_supported ? "hardware" : "software"); + } + + if (rte_eth_timesync_read_time(ptp->portid, &now) != 0) + return; + local = timespec64_to_ns(&now); + + /* Large offset: step the clock directly and (re)start the servo. */ + if (offset >= PTP_STEP_THRESHOLD_NS || offset <= -PTP_STEP_THRESHOLD_NS) { + rte_eth_timesync_adjust_time(ptp->portid, offset); + servo->last_offset = 0; + servo->last_local = local; + if (servo->count == 0) + servo->count = 1; + return; + } + + switch (servo->count) { + case 0: + /* First sample: establish the baseline only. */ + servo->last_offset = offset; + servo->last_local = local; + servo->count = 1; + return; + case 1: + /* Second sample: seed the drift estimate from the slope. */ + if (local > servo->last_local) + servo->drift_ppb = 1e9 * + (double)(offset - servo->last_offset) / + (double)(local - servo->last_local); + servo->count = 2; + break; + default: + ki_term = PTP_SERVO_KI * (double)offset; + servo->drift_ppb += ki_term; + break; + } + + ppb = PTP_SERVO_KP * (double)offset + servo->drift_ppb; + + if (servo->freq_adj_supported == 1) { + rte_eth_timesync_adjust_freq(ptp->portid, ppb_to_scaled_ppm(ppb)); + } else if (local > servo->last_local) { + /* Realize the frequency correction as a phase step. */ + double dt = (double)(local - servo->last_local); + + rte_eth_timesync_adjust_time(ptp->portid, + (int64_t)(ppb * dt / 1e9)); + } + + servo->last_offset = offset; + servo->last_local = local; +} + /* * Parse the PTP SYNC message. */ @@ -507,8 +612,7 @@ parse_drsp(struct ptpv2_time_receiver_ordinary *ptp) /* Evaluate the delta for adjustment. */ ptp->delta = delta_eval(ptp); - rte_eth_timesync_adjust_time(ptp->portid, - ptp->delta); + clock_servo(ptp, ptp->delta); ptp->current_ptp_port = ptp->portid; @@ -576,6 +680,10 @@ lcore_main(void) printf("\nCore %u Waiting for SYNC packets. [Ctrl+C to quit]\n", rte_lcore_id()); + /* Hardware frequency support is probed on the first adjustment. */ + for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) + ptp_servo[portid].freq_adj_supported = -1; + /* Run until the application is quit or killed. */ while (!force_quit) { -- 2.43.0
