linux-kernel - Re: [PATCH net-next 2/3] net: dsa: mv88e6xxx: extend PTP gettime function to read system clock

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Date:   Mon, 19 Aug 2019 19:34:41 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Hubert Feurstein <h.feurstein@...il.com>
Cc:     netdev <netdev@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Richard Cochran <richardcochran@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next 2/3] net: dsa: mv88e6xxx: extend PTP gettime
 function to read system clock

On Mon, Aug 19, 2019 at 07:14:25PM +0200, Hubert Feurstein wrote:
> Hi Andrew,
> 
> Am Mo., 19. Aug. 2019 um 15:27 Uhr schrieb Andrew Lunn <andrew@...n.ch>:
> >
> > > @@ -45,7 +45,8 @@ static int mv88e6xxx_smi_direct_write(struct mv88e6xxx_chip *chip,
> > >  {
> > >       int ret;
> > >
> > > -     ret = mdiobus_write_nested(chip->bus, dev, reg, data);
> > > +     ret = mdiobus_write_sts_nested(chip->bus, dev, reg, data,
> > > +                                    chip->ptp_sts);
> > >       if (ret < 0)
> > >               return ret;
> > >
> >
> > Please also make a similar change to mv88e6xxx_smi_indirect_write().
> > The last write in that function should be timestamped.
> Since it is already the last write it should be already ok (The
> mv88e6xxx_smi_indirect_write
> calls the mv88e6xxx_smi_direct_write which initiates the timestamping).

Hi Hubert

But you are also time stamping the first write as well. And it seems
like it is not completely for free. So it would be nice to limit it to
the write which actually matters.

    Andrew