linux-kernel - Re: [PATCH v3 net-next 00/17] PTP support for the SJA1105 DSA driver

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Date:   Fri, 7 Jun 2019 12:43:05 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 net-next 00/17] PTP support for the SJA1105 DSA driver

On Fri, 7 Jun 2019 at 06:32, Richard Cochran <richardcochran@...il.com> wrote:
>
> On Thu, Jun 06, 2019 at 04:40:19PM +0300, Vladimir Oltean wrote:
> > Plain and simply because it doesn't work very well.
> > Even phc2sys from the system clock to the hardware (no timestamps
> > involved) has trouble staying put (under 1000 ns offset).
> > And using the hardware-corrected timestamps triggers a lot of clockchecks.
>
> It sounds like a bug in reading or adjusting the HW clock.  Is the HW
> clock stable when you don't adjust its frequency?

How can I tell that for sure?

>
> Thanks,
> Richard