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

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Date:   Fri, 28 Apr 2023 10:51:40 +0200
From:   Köry Maincent <kory.maincent@...tlin.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        davem@...emloft.net, f.fainelli@...il.com, hkallweit1@...il.com,
        kuba@...nel.org, netdev@...r.kernel.org, richardcochran@...il.com,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>
Subject: Re: [PATCH RFC net-next] net: phy: add Marvell PHY PTP support
 [multicast/DSA issues]

On Thu, 27 Apr 2023 18:50:47 +0200
Andrew Lunn <andrew@...n.ch> wrote:

> > As we are currently moving forward on PTP core to resolve this issue, I
> > would like to investigate your PHY PTP patch in parallel. Indeed it does
> > not work very well on my side.
> > 
> > The PTP UDP v4 and v6 work only if I add "--tx_timestamp_timeout 20" and the
> > PTP IEEE 802.3 (802.1AS) does not work at all.
> > On PTP IEEE 802.3 network transport ("ptp4l -2") I get continuously rx
> > timestamp overrun:
> > Marvell 88E1510 ff0d0000.ethernet-ffffffff:01: rx timestamp overrun (5)
> > Marvell 88E1510 ff0d0000.ethernet-ffffffff:01: rx timestamp overrun (5)
> > 
> > I know it's been a long time but does it ring a bell on your memory?  
> 
> How are you talking to the PHY? I had issues with slow MDIO busses,
> especially those embedded within an Ethernet switch. You end up with
> MDIO over MDIO which has a lot of latency. I _think_ i added some
> patches to ptp4l to deal with this, but i forget exactly what landed.

I am talking to the PHY through a simple MDIO bus.
The current PTP support from Russell does not support interrupts. Could it be
the cause of needing bigger tx timestamp timeout?