linux-kernel - Re: [PATCH 1/2] net: stmmac: retain PTP-clock at hwtstamp

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Message-ID: <20201217022236.GA28883@hoboy.vegasvil.org>
Date:   Wed, 16 Dec 2020 18:22:36 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Holger Assmann <h.assmann@...gutronix.de>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Rayagond Kokatanur <rayagond@...avyalabs.com>,
        kernel@...gutronix.de, Michael Olbrich <m.olbrich@...gutronix.de>,
        Ahmad Fatoum <a.fatoum@...gutronix.de>,
        Jose Abreu <Jose.Abreu@...opsys.com>, netdev@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] net: stmmac: retain PTP-clock at hwtstamp_set

On Wed, Dec 16, 2020 at 05:13:34PM -0800, Jakub Kicinski wrote:
> On Wed, 16 Dec 2020 12:32:38 +0100 Holger Assmann wrote:
> > As it is, valid SIOCSHWTSTAMP ioctl calls - i.e. enable/disable time
> > stamping or changing filter settings - lead to synchronization of the
> > NIC's hardware clock with CLOCK_REALTIME. This might be necessary
> > during system initialization, but at runtime, when the PTP clock has
> > already been synchronized to a grand master, a reset of the timestamp
> > settings might result in a clock jump.

+1 for keeping the PHC time continuous.

> Please remember to CC Richard, the PTP maintainer.

+1 to that, too!

Thanks,
Richard