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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2024-05-02 at 14:10 -0700, Mahesh Bandewar wrote: > 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. >=20 > 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. >=20 > 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. >=20 > 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. >=20 > Signed-off-by: Mahesh Bandewar LGTM, but let's wait a bit for Richard ack. @Richard, could you please have look? Paolo