From c259acab839e57eab0318f32da4ae803a8d59397 Mon Sep 17 00:00:00 2001 From: Mahesh Bandewar Date: Wed, 4 Sep 2024 07:13:05 -0700 Subject: ptp/ioctl: support MONOTONIC{,_RAW} timestamps for PTP_SYS_OFFSET_EXTENDED The ability to read the PHC (Physical Hardware Clock) alongside multiple system clocks is currently dependent on the specific hardware architecture. This limitation restricts the use of PTP_SYS_OFFSET_PRECISE to certain hardware configurations. The generic soultion which would work across all architectures is to read the PHC along with the latency to perform PHC-read as offered by PTP_SYS_OFFSET_EXTENDED which provides pre and post timestamps. However, these timestamps are currently limited to the CLOCK_REALTIME timebase. Since CLOCK_REALTIME is affected by NTP (or similar time synchronization services), it can experience significant jumps forward or backward. This hinders the precise latency measurements that PTP_SYS_OFFSET_EXTENDED is designed to provide. This problem could be addressed by supporting MONOTONIC_RAW timestamps within PTP_SYS_OFFSET_EXTENDED. Unlike CLOCK_REALTIME or CLOCK_MONOTONIC, the MONOTONIC_RAW timebase is unaffected by NTP adjustments. This enhancement can be implemented by utilizing one of the three reserved words within the PTP_SYS_OFFSET_EXTENDED struct to pass the clock-id for timestamps. The current behavior aligns with clock-id for CLOCK_REALTIME timebase (value of 0), ensuring backward compatibility of the UAPI. Signed-off-by: Mahesh Bandewar Signed-off-by: Vadim Fedorenko Signed-off-by: David S. Miller --- include/linux/ptp_clock_kernel.h | 36 ++++++++++++++++++++++++++++++++---- 1 file changed, 32 insertions(+), 4 deletions(-) (limited to 'include/linux') diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h index 6e4b8206c7d0..c892d22ce0a7 100644 --- a/include/linux/ptp_clock_kernel.h +++ b/include/linux/ptp_clock_kernel.h @@ -47,10 +47,12 @@ struct system_device_crosststamp; * struct ptp_system_timestamp - system time corresponding to a PHC timestamp * @pre_ts: system timestamp before capturing PHC * @post_ts: system timestamp after capturing PHC + * @clockid: clock-base used for capturing the system timestamps */ struct ptp_system_timestamp { struct timespec64 pre_ts; struct timespec64 post_ts; + clockid_t clockid; }; /** @@ -457,14 +459,40 @@ static inline ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp, static inline void ptp_read_system_prets(struct ptp_system_timestamp *sts) { - if (sts) - ktime_get_real_ts64(&sts->pre_ts); + if (sts) { + switch (sts->clockid) { + case CLOCK_REALTIME: + ktime_get_real_ts64(&sts->pre_ts); + break; + case CLOCK_MONOTONIC: + ktime_get_ts64(&sts->pre_ts); + break; + case CLOCK_MONOTONIC_RAW: + ktime_get_raw_ts64(&sts->pre_ts); + break; + default: + break; + } + } } static inline void ptp_read_system_postts(struct ptp_system_timestamp *sts) { - if (sts) - ktime_get_real_ts64(&sts->post_ts); + if (sts) { + switch (sts->clockid) { + case CLOCK_REALTIME: + ktime_get_real_ts64(&sts->post_ts); + break; + case CLOCK_MONOTONIC: + ktime_get_ts64(&sts->post_ts); + break; + case CLOCK_MONOTONIC_RAW: + ktime_get_raw_ts64(&sts->post_ts); + break; + default: + break; + } + } } #endif -- cgit v1.2.3