Currently HW support of ptp/timesync solutions in network PHY chips can be implemented with two different approaches, the timestamp maybe latched either at the beginning or after the Start of Frame Delimiter (SFD) [1].
Allow ptp device drivers to provide user with control over the HW timestamp latch point with ptp sysfs ABI. Provide a new file under sysfs ptp device (/sys/class/ptp/ptp<N>/ts_point). The file is available for the user, if the device driver implements at least one of newly provided callbacks. If the file is not provided the user shall find a PHY timestamp latch point within the HW vendor specification. The file is designed for root user/group access only, as the read for regular user could impact performance of the ptp device. Usage, examples: ** Obtain current state: $ cat /sys/class/ptp/ptp<N>/ts_point Command returns enum/integer: * 1 - timestamp latched by PHY at the beginning of SFD, * 2 - timestamp latched by PHY after the SFD, * None - callback returns error to the user. ** Configure timestamp latch point at the beginning of SFD: $ echo 1 > /sys/class/ptp/ptp<N>/ts_point ** Configure timestamp latch point after the SFD: $ echo 2 > /sys/class/ptp/ptp<N>/ts_point [1] https://www.ieee802.org/3/cx/public/april20/tse_3cx_01_0420.pdf Reviewed-by: Aleksandr Loktionov <aleksandr.loktio...@intel.com> Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalew...@intel.com> --- v3: - max value of enum ptp_ts_point is also enumerated, - move enum ptp_ts_point to uapi, - add NONE value to enum ptp_ts_point, to make clear that value was not provided, thus allow further extension of ethtool netlink. --- Documentation/ABI/testing/sysfs-ptp | 12 ++++++++ drivers/ptp/ptp_sysfs.c | 44 +++++++++++++++++++++++++++++ include/linux/ptp_clock_kernel.h | 12 ++++++++ include/uapi/linux/ptp_clock.h | 18 ++++++++++++ 4 files changed, 86 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-ptp b/Documentation/ABI/testing/sysfs-ptp index 9c317ac7c47a..063b3e20386e 100644 --- a/Documentation/ABI/testing/sysfs-ptp +++ b/Documentation/ABI/testing/sysfs-ptp @@ -140,3 +140,15 @@ Description: PPS events to the Linux PPS subsystem. To enable PPS events, write a "1" into the file. To disable events, write a "0" into the file. + +What: /sys/class/ptp/ptp<N>/ts_point +Date: October 2024 +Contact: Arkadiusz Kubalewski <arkadiusz.kubalew...@intel.com> +Description: + This file provides control over the point in time in + which the HW timestamp is latched. As specified in IEEE + 802.3cx, the latch point can be either at the beginning + or after the end of Start of Frame Delimiter (SFD). + Value "1" means the timestamp is latched at the + beginning of the SFD. Value "2" means that timestamp is + latched after the end of SFD. diff --git a/drivers/ptp/ptp_sysfs.c b/drivers/ptp/ptp_sysfs.c index 6b1b8f57cd95..2f3f28edbbfd 100644 --- a/drivers/ptp/ptp_sysfs.c +++ b/drivers/ptp/ptp_sysfs.c @@ -28,6 +28,46 @@ static ssize_t max_phase_adjustment_show(struct device *dev, } static DEVICE_ATTR_RO(max_phase_adjustment); +static ssize_t ts_point_show(struct device *dev, struct device_attribute *attr, + char *page) +{ + struct ptp_clock *ptp = dev_get_drvdata(dev); + enum ptp_ts_point point; + int err; + + if (!ptp->info->get_ts_point) + return -EOPNOTSUPP; + err = ptp->info->get_ts_point(ptp->info, &point); + if (err) + return err; + + return sysfs_emit(page, "%d\n", point); +} + +static ssize_t ts_point_store(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + struct ptp_clock *ptp = dev_get_drvdata(dev); + enum ptp_ts_point point; + int err; + u8 val; + + if (!ptp->info->set_ts_point) + return -EOPNOTSUPP; + if (kstrtou8(buf, 0, &val)) + return -EINVAL; + if (val <= PTP_TS_POINT_NONE || val > PTP_TS_POINT_MAX) + return -EINVAL; + point = val; + + err = ptp->info->set_ts_point(ptp->info, point); + if (err) + return err; + + return count; +} +static DEVICE_ATTR(ts_point, 0660, ts_point_show, ts_point_store); + #define PTP_SHOW_INT(name, var) \ static ssize_t var##_show(struct device *dev, \ struct device_attribute *attr, char *page) \ @@ -335,6 +375,7 @@ static struct attribute *ptp_attrs[] = { &dev_attr_pps_enable.attr, &dev_attr_n_vclocks.attr, &dev_attr_max_vclocks.attr, + &dev_attr_ts_point.attr, NULL }; @@ -363,6 +404,9 @@ static umode_t ptp_is_attribute_visible(struct kobject *kobj, } else if (attr == &dev_attr_max_phase_adjustment.attr) { if (!info->adjphase || !info->getmaxphase) mode = 0; + } else if (attr == &dev_attr_ts_point.attr) { + if (!info->get_ts_point && !info->set_ts_point) + mode = 0; } return mode; diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h index c892d22ce0a7..d48619c7c60a 100644 --- a/include/linux/ptp_clock_kernel.h +++ b/include/linux/ptp_clock_kernel.h @@ -159,6 +159,14 @@ struct ptp_system_timestamp { * scheduling time (>=0) or negative value in case further * scheduling is not required. * + * @set_ts_point: Request change of timestamp latch point, as the timestamp + * could be latched at the beginning or after the end of start + * frame delimiter (SFD), as described in IEEE 802.3cx + * specification. + * + * @get_ts_point: Obtain the timestamp measurement latch point, counterpart of + * .set_ts_point() for getting currently configured value. + * * Drivers should embed their ptp_clock_info within a private * structure, obtaining a reference to it using container_of(). * @@ -195,6 +203,10 @@ struct ptp_clock_info { int (*verify)(struct ptp_clock_info *ptp, unsigned int pin, enum ptp_pin_function func, unsigned int chan); long (*do_aux_work)(struct ptp_clock_info *ptp); + int (*set_ts_point)(struct ptp_clock_info *ptp, + enum ptp_ts_point point); + int (*get_ts_point)(struct ptp_clock_info *ptp, + enum ptp_ts_point *point); }; struct ptp_clock; diff --git a/include/uapi/linux/ptp_clock.h b/include/uapi/linux/ptp_clock.h index 18eefa6d93d6..11a9dad9db00 100644 --- a/include/uapi/linux/ptp_clock.h +++ b/include/uapi/linux/ptp_clock.h @@ -253,4 +253,22 @@ struct ptp_extts_event { unsigned int rsv[2]; /* Reserved for future use. */ }; +/** + * enum ptp_ts_point - possible timestamp latch points (IEEE 802.3cx) + * + * @PTP_TS_POINT_NONE: no timestamp latch point was provided + * @PTP_TS_POINT_SFD: timestamp latched at the beginning of sending Start + * of Frame Delimiter (SFD) + * @PTP_TS_POINT_POST_SFD: timestamp latched after the end of sending Start + * of Frame Delimiter (SFD) + */ +enum ptp_ts_point { + PTP_TS_POINT_NONE = 0, + PTP_TS_POINT_SFD, + PTP_TS_POINT_POST_SFD, + + /* private: */ + PTP_TS_POINT_MAX +}; + #endif -- 2.38.1
