如何使用主时钟同步Linux工控机

在一些使用场景中，我们需要使用主时钟来同步工控机或PC机。如下图所示。下面我们介绍一下如何在利用飞灵科技的FlySync 主时钟同步一个Linux 主机。

在工控机安装linuxprp 软件包

使用apt 安装linuxptp：sudo apt-get install linuxptp 或者其他方式。

使用ethtool 工具查看主机网口是否具有硬件时间戳能力

root@pc:~$ ethtool -T eth0
Time stamping parameters for eth0:
Capabilities:
        hardware-transmit     (SOF_TIMESTAMPING_TX_HARDWARE)
        software-transmit     (SOF_TIMESTAMPING_TX_SOFTWARE)
        hardware-receive      (SOF_TIMESTAMPING_RX_HARDWARE)
        software-receive      (SOF_TIMESTAMPING_RX_SOFTWARE)
        software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
        hardware-raw-clock    (SOF_TIMESTAMPING_RAW_HARDWARE)
PTP Hardware Clock: 0
Hardware Transmit Timestamp Modes:
        off                   (HWTSTAMP_TX_OFF)
        on                    (HWTSTAMP_TX_ON)
Hardware Receive Filter Modes:
        none                  (HWTSTAMP_FILTER_NONE)
        all                   (HWTSTAMP_FILTER_ALL)
        ptpv1-l4-sync         (HWTSTAMP_FILTER_PTP_V1_L4_SYNC)
        ptpv1-l4-delay-req    (HWTSTAMP_FILTER_PTP_V1_L4_DELAY_REQ)
        ptpv2-l4-sync         (HWTSTAMP_FILTER_PTP_V2_L4_SYNC)
        ptpv2-l4-delay-req    (HWTSTAMP_FILTER_PTP_V2_L4_DELAY_REQ)
        ptpv2-l2-sync         (HWTSTAMP_FILTER_PTP_V2_L2_SYNC)
        ptpv2-l2-delay-req    (HWTSTAMP_FILTER_PTP_V2_L2_DELAY_REQ)
        ptpv2-event           (HWTSTAMP_FILTER_PTP_V2_EVENT)
        ptpv2-sync            (HWTSTAMP_FILTER_PTP_V2_SYNC)
        ptpv2-delay-req       (HWTSTAMP_FILTER_PTP_V2_DELAY_REQ)

从上面可以看出，网口eth0支持硬件和软件时间戳，并且对应的ptp时钟为/dev/ptp0。

查看主时钟配置的参数

同步工控机上的时间 

root@pc:~$ sudo ptp4l -i eth0 -p /dev/ptp1 -s -m  -H -E  
ptp4l[8706866.391]: selected /dev/ptp1 as PTP clock
ptp4l[8706866.393]: port 1: INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[8706866.393]: port 0: INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[8706867.209]: port 1: new foreign master 180373.fffe.31a803-1
ptp4l[8706871.209]: selected best master clock 180373.fffe.31a803
ptp4l[8706871.209]: running in a temporal vortex
ptp4l[8706871.209]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
ptp4l[8706872.214]: master offset       2185 s0 freq   -7043 path delay     13428
ptp4l[8706873.214]: master offset       1977 s2 freq   -7251 path delay     13428
ptp4l[8706873.214]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
ptp4l[8706874.214]: master offset       2384 s2 freq   -4867 path delay     13369
ptp4l[8706875.214]: master offset        364 s2 freq   -6172 path delay     13428
ptp4l[8706876.214]: master offset       -588 s2 freq   -7015 path delay     13579
ptp4l[8706877.214]: master offset       -701 s2 freq   -7304 path delay     13444
ptp4l[8706878.214]: master offset       -139 s2 freq   -6952 path delay     13425
ptp4l[8706879.215]: master offset       -202 s2 freq   -7057 path delay     13428
ptp4l[8706880.215]: master offset       -520 s2 freq   -7436 path delay     13453
ptp4l[8706881.215]: master offset         -9 s2 freq   -7081 path delay     13434
ptp4l[8706882.215]: master offset        127 s2 freq   -6947 path delay     13410
ptp4l[8706883.215]: master offset         62 s2 freq   -6974 path delay  

获取同步后的时间

#include <time.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#define CLOCKFD 3
#define FD_TO_CLOCKID(fd)   ((~(clockid_t) (fd) << 3) | CLOCKFD)
#define CLOCKID_TO_FD(clk)  ((unsigned int) ~((clk) >> 3))

int
main(int argc, char *argv[])
{
    struct timespec ts;
    clockid_t clkid;
    int fd;

    fd = open("/dev/ptp0", O_RDWR);
    clkid = FD_TO_CLOCKID(fd);

    if (clock_gettime(clkid, &ts) == -1) {
        perror("clock_gettime");
        exit(EXIT_FAILURE);
    }
    printf("Date: %s \n", ctime(&ts.tv_sec));

    exit(EXIT_SUCCESS);
}