From: Richard Cochran <richardcochran@gmail.com>
To: Sergey Organov <sorganov@gmail.com>
Cc: Vladimir Oltean <olteanv@gmail.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Fugang Duan <fugang.duan@nxp.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>
Subject: Re: [PATCH 3/5] net: fec: initialize clock with 0 rather than current kernel time
Date: Wed, 8 Jul 2020 07:48:03 -0700 [thread overview]
Message-ID: <20200708144803.GB13374@hoboy> (raw)
In-Reply-To: <87mu4a9o8m.fsf@osv.gnss.ru>
On Wed, Jul 08, 2020 at 03:37:29PM +0300, Sergey Organov wrote:
> Richard Cochran <richardcochran@gmail.com> writes:
>
> > On Mon, Jul 06, 2020 at 06:27:21PM +0300, Vladimir Oltean wrote:
> >> There's no correct answer, I'm afraid. Whatever the default value of the
> >> clock may be, it's bound to be confusing for some reason, _if_ the
> >> reason why you're investigating it in the first place is a driver bug.
> >> Also, I don't really see how your change to use Jan 1st 1970 makes it
> >> any less confusing.
> >
> > +1
> >
> > For a PHC, the user of the clock must check the PTP stack's
> > synchronization flags via the management interface to know the status
> > of the time signal.
>
> Actually, as I just realized, the right solution for my original problem
> would rather be adding PTP clock ID that time stamped Ethernet packet to
> the Ethernet hardware time stamp (see my previous reply as well).
I think you misunderstood my point. I wasn't commenting on the
"stacked" MAC/PHY/DSA time stamp issue in the kernel.
I am talking about the question of whether to initialize the PHC time
to zero (decades off from TAI) or ktime (likely about 37 seconds off
from TAI). It does not really matter, because the user must not guess
whether the time is valid based on the value. Instead, the user
should query the relevant PTP data sets in a "live" online manner.
For example, to tell whether a PHC is synchronized to anything at all,
you need to check PORT_DATA_SET.portState and probably also
CURRENT_DATA_SET.offsetFromMaster depending on your needs.
In addition, if you care about global time, you need to check:
TIME_PROPERTIES_DATA_SET
currentUtcOffset
currentUtcOffsetValid
ptpTimescale
timeTraceable
frequencyTraceable
Thanks,
Richard
next prev parent reply other threads:[~2020-07-08 14:48 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-06 14:26 [PATCH 0/5] net: fec: fix external PTP PHY support Sergey Organov
2020-07-06 14:26 ` [PATCH 1/5] net: fec: properly support external PTP PHY for hardware time stamping Sergey Organov
2020-07-06 15:08 ` Vladimir Oltean
2020-07-06 15:21 ` Sergey Organov
2020-07-06 15:47 ` Vladimir Oltean
2020-07-06 18:33 ` Sergey Organov
2020-07-07 7:04 ` Vladimir Oltean
2020-07-07 15:29 ` Sergey Organov
2020-07-08 11:00 ` Richard Cochran
2020-07-08 10:55 ` Richard Cochran
2020-07-06 14:26 ` [PATCH 2/5] net: fec: enable to use PPS feature without " Sergey Organov
2020-07-07 4:05 ` [EXT] " Andy Duan
2020-07-07 14:29 ` Sergey Organov
2020-07-06 14:26 ` [PATCH 3/5] net: fec: initialize clock with 0 rather than current kernel time Sergey Organov
2020-07-06 15:27 ` Vladimir Oltean
2020-07-06 18:24 ` Sergey Organov
2020-07-07 6:36 ` Vladimir Oltean
2020-07-07 16:07 ` Sergey Organov
2020-07-07 16:43 ` Vladimir Oltean
2020-07-07 17:09 ` Sergey Organov
2020-07-07 17:12 ` Vladimir Oltean
2020-07-07 17:56 ` Sergey Organov
2020-07-08 11:15 ` Richard Cochran
2020-07-08 12:14 ` Sergey Organov
2020-07-08 11:11 ` Richard Cochran
2020-07-08 11:04 ` Richard Cochran
2020-07-08 12:24 ` Sergey Organov
2020-07-08 12:37 ` Sergey Organov
2020-07-08 14:48 ` Richard Cochran [this message]
2020-07-08 17:18 ` Sergey Organov
2020-07-06 14:26 ` [PATCH 4/5] net: fec: get rid of redundant code in fec_ptp_set() Sergey Organov
2020-07-07 4:08 ` [EXT] " Andy Duan
2020-07-07 14:43 ` Sergey Organov
2020-07-08 5:34 ` Andy Duan
2020-07-08 8:48 ` Sergey Organov
2020-07-08 8:57 ` Andy Duan
2020-07-08 12:26 ` Sergey Organov
2020-07-06 14:26 ` [PATCH 5/5] net: fec: replace snprintf() with strlcpy() in fec_ptp_init() Sergey Organov
2020-07-11 12:08 ` [PATCH v2 net] net: fec: fix hardware time stamping by external devices Sergey Organov
2020-07-11 23:19 ` Vladimir Oltean
2020-07-12 14:16 ` Sergey Organov
2020-07-12 14:47 ` Andrew Lunn
2020-07-12 15:01 ` Vladimir Oltean
2020-07-12 17:29 ` Sergey Organov
2020-07-12 19:33 ` Vladimir Oltean
2020-07-12 22:32 ` Sergey Organov
2020-07-12 23:15 ` Vladimir Oltean
2020-07-14 12:39 ` Sergey Organov
2020-07-14 14:23 ` Vladimir Oltean
2020-07-14 14:35 ` Sergey Organov
2020-07-14 14:44 ` Vladimir Oltean
2020-07-14 16:18 ` Sergey Organov
2020-07-14 14:01 ` Richard Cochran
2020-07-14 14:27 ` Sergey Organov
2020-07-14 16:28 ` [PATCH v3 " Sergey Organov
2020-07-16 18:24 ` Jakub Kicinski
2020-07-16 20:38 ` Sergey Organov
2020-07-16 21:06 ` Jakub Kicinski
2020-07-16 21:18 ` Sergey Organov
2020-07-15 15:42 ` [PATCH net-next v2 0/4] net: fec: a few improvements Sergey Organov
2020-07-15 15:42 ` [PATCH net-next v2 1/4] net: fec: enable to use PPS feature without time stamping Sergey Organov
2020-07-15 15:42 ` [PATCH net-next v2 2/4] net: fec: initialize clock with 0 rather than current kernel time Sergey Organov
2020-07-15 15:42 ` [PATCH net-next v2 3/4] net: fec: get rid of redundant code in fec_ptp_set() Sergey Organov
2020-07-15 15:43 ` [PATCH net-next v2 4/4] net: fec: replace snprintf() with strlcpy() in fec_ptp_init() Sergey Organov
2020-07-16 3:00 ` [EXT] [PATCH net-next v2 0/4] net: fec: a few improvements Andy Duan
2020-07-16 18:37 ` Jakub Kicinski
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