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

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Message-ID: <20190531160909.jh43saqvichukv7p@localhost>
Date:   Fri, 31 May 2019 09:09:09 -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 Fri, May 31, 2019 at 06:23:34PM +0300, Vladimir Oltean wrote:
> You mean to queue it and subvert DSA's own RX timestamping callback?

No, use the callback.

> Why would I do that? Just so as not to introduce my .can_timestamp
> callback?

Right, the .can_timestamp is unneeded, AFAICT.
 
> > Now I'm starting to understand your series.  I think it can be done in
> > simpler way...
> >
> > sja1105_rcv_meta_state_machine - can and should be at the driver level
> > and not at the port level.
> >
> 
> Can: yes. Should: why?

To keep it simple and robust.
 
> One important aspect makes this need be a little bit more complicated:
> reconstructing these RX timestamps.
> You see, there is a mutex on the SPI bus, so in practice I do need the
> sja1105_port_rxtstamp_work for exactly this purpose - to read the
> timestamping clock over SPI.

Sure.  But you schedule the work after a META frame.  And no busy
waiting is needed.
 
Thanks,
Richard