netdev - Re: [PATCH RFC net-next] net: phy: add Marvell PHY PTP support [multicast/DSA issues]

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Message-ID: <20200730155006.GA28298@hoboy>
Date:   Thu, 30 Jul 2020 08:50:06 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH RFC net-next] net: phy: add Marvell PHY PTP support
 [multicast/DSA issues]

On Thu, Jul 30, 2020 at 12:54:19PM +0100, Russell King - ARM Linux admin wrote:
> So, something in the IPv4 layer on ARM64 is silently discarding
> multicast UDP PTP packets, and I've no idea what... and I'm coming to
> the conclusion that this is all way too much effort and way too
> unreliable to be worth spending any more time trying to make work.

I've also seen this on the Marvell switch.  I'm not sure if the root
cause is in the Linux stack or in the mcast forwarding logic in the
switch.  Using the Marvell, I can make a layer2 TC or a UDPv4 BC, but
not a UDPv4 TC.

I haven't had time to dig deeper, and I think many people are happy
with a layer2 TC as that is called out in the TSN world.

Thanks,
Richard