diff options
| author | Mahesh Bandewar <maheshb@google.com> | 2024-09-04 07:13:05 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2024-09-08 18:40:33 +0100 |
| commit | c259acab839e57eab0318f32da4ae803a8d59397 (patch) | |
| tree | 2d04bad4ad9273e95fc0bd221bd70ec91ac3d3cd /include/linux/ptp_clock_kernel.h | |
| parent | d5c4546062fd6f5dbce575c7ea52ad66d1968678 (diff) | |
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 <maheshb@google.com>
Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/ptp_clock_kernel.h')
| -rw-r--r-- | include/linux/ptp_clock_kernel.h | 36 |
1 files changed, 32 insertions, 4 deletions
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 |