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

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Date:   Fri, 31 May 2019 08:11:51 -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 05:27:15PM +0300, Vladimir Oltean wrote:
> On Fri, 31 May 2019 at 17:08, Richard Cochran <richardcochran@...il.com> wrote:
> > This can be done simply using a data structure in the driver with an
> > appropriate locking mechanism.  Then you don't have to worry which
> > core the driver code runs on.
> >
> 
> Actually you do. DSA is special because it is not the first net device
> in the RX path that processes the frames. Something needs to be done
> on the master port.

Before you said,

	the switch in its great wisdom mangles bytes 01-1B-19-xx-xx-00
	of the DMAC to place the switch id and source port there (a
	rudimentary tagging mechanism).

So why not simply save each frame in a per-switch/port data structure?

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.

sja1105_port_rxtstamp_work - isn't needed at all.

How about this?

1. When the driver receives a deferred PTP frame, save it into a
   per-switch,port slot at the driver (not port) level.

2. When the driver receives a META frame, match it to the
   per-switch,port slot.  If there is a PTP frame in that slot, then
   deliver it with the time stamp from the META frame.

Thanks,
Richard