linux-kernel - Re: [PATCH net-next 0/5] PTP support for the SJA1105 DSA driver

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Message-ID: <20190530150557.iur7fruhyf5bs3qw@localhost>
Date:   Thu, 30 May 2019 08:05:57 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        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 net-next 0/5] PTP support for the SJA1105 DSA driver

On Thu, May 30, 2019 at 05:57:30PM +0300, Vladimir Oltean wrote:
> On Thu, 30 May 2019 at 17:30, Richard Cochran <richardcochran@...il.com> wrote:
> >
> > Not necessarily.  If two frames that arrive at nearly the same time
> > get their timestamps mixed up, that would be enough to break the time
> > values but without breaking your state machine.
> >
> 
> This doesn't exactly sound like the type of thing I can check for.

And that is why it cannot work.

> The RX and TX timestamps *are* monotonically increasing with time for
> all frames when I'm printing them in the {rx,tx}tstamp callbacks.

But are the frames received in the same order?  What happens your MAC
drops a frame?
 
> The driver returns free-running timestamps altered with a timecounter
> frequency set by adjfine and offset set by adjtime.

That should be correct.

Thanks,
Richard