From: Miroslav Lichvar <mlichvar@redhat.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: netdev@vger.kernel.org, Yangbo Lu <yangbo.lu@nxp.com>
Subject: Re: [PATCH net-next 5/5] ptp: start virtual clocks at current system time.
Date: Mon, 31 Jan 2022 11:21:08 +0100 [thread overview]
Message-ID: <Yfe4FPHbFjc6FoTa@localhost> (raw)
In-Reply-To: <20220127220116.GB26514@hoboy.vegasvil.org>
On Thu, Jan 27, 2022 at 02:01:16PM -0800, Richard Cochran wrote:
> On Thu, Jan 27, 2022 at 12:45:36PM +0100, Miroslav Lichvar wrote:
> > When a virtual clock is being created, initialize the timecounter to the
> > current system time instead of the Unix epoch to avoid very large steps
> > when the clock will be synchronized.
>
> I think we agreed that, going forward, new PHC drivers should start at
> zero (1970) instead of TAI - 37.
I tried to find the discussion around this decision, but failed. Do
you have a link?
To me, it seems very strange to start the PHC at 0. It makes the
initial clock correction unnecessarily larger by ~7 orders of
magnitude. The system clock is initialized from the RTC, which can
have an error comparable to the TAI-UTC offset, especially if the
machine was turned off for a longer period of time, so why not
initialize the PHC from the system time? The error is much smaller
than billions of seconds.
--
Miroslav Lichvar
next prev parent reply other threads:[~2022-01-31 10:21 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-27 11:45 [PATCH net-next 0/5] Virtual PTP clock improvements and fix Miroslav Lichvar
2022-01-27 11:45 ` [PATCH net-next 1/5] ptp: unregister virtual clocks when unregistering physical clock Miroslav Lichvar
2022-01-27 23:58 ` Vinicius Costa Gomes
2022-01-31 10:07 ` Miroslav Lichvar
2022-01-31 12:41 ` Vladimir Oltean
2022-01-27 11:45 ` [PATCH net-next 2/5] ptp: increase maximum adjustment of virtual clocks Miroslav Lichvar
2022-01-27 11:45 ` [PATCH net-next 3/5] ptp: add gettimex64() to " Miroslav Lichvar
2022-01-27 11:45 ` [PATCH net-next 4/5] ptp: add getcrosststamp() " Miroslav Lichvar
2022-01-27 11:45 ` [PATCH net-next 5/5] ptp: start virtual clocks at current system time Miroslav Lichvar
2022-01-27 22:01 ` Richard Cochran
2022-01-31 10:21 ` Miroslav Lichvar [this message]
2022-01-31 16:32 ` Richard Cochran
2022-02-01 8:42 ` Miroslav Lichvar
2022-02-01 19:10 ` Richard Cochran
2022-02-01 19:03 ` Richard Cochran
2022-02-02 9:07 ` Miroslav Lichvar
2022-01-27 22:02 ` [PATCH net-next 0/5] Virtual PTP clock improvements and fix Richard Cochran
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