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

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Date:   Thu, 27 Apr 2023 17:13:06 +0200
From:   Köry Maincent <kory.maincent@...tlin.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     andrew@...n.ch, 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]

Hello Russell,

On Mon, 27 Feb 2023 15:20:05 +0000
"Russell King (Oracle)" <linux@...linux.org.uk> wrote:

> On Mon, Feb 27, 2023 at 03:40:37PM +0100, Köry Maincent wrote:
> > Hello RMK,
> >   
> > > Hence why I'm at the point of giving up; I don't see that PTP will be
> > > of very limited benefit on my network with all these issues, and in
> > > any case, NTP has been "good enough" for the last 20+ years.  Given
> > > that only a limited number of machines will be able to implement PTP
> > > support anyway, NTP will have to run along side it.  
> > 
> > I see this patch has been abandoned.
> > I am testing it with a ZynqMP board (macb ethernet) and it seems to more or
> > less work. It got tx timestamp timeout at initialization but after some
> > times (~20 seconds) ptp4l manages to set it working. Also the IEEE 802.3
> > network PTP mode is not working, it constantly throw rx timestamp overrun
> > errors.
> > I will aim at fixing these issues and adding support to interrupts. It
> > would be good to have it accepted mainline. What do you think is missing
> > for that?  
> 
> It isn't formally abandoned, but is permanently on-hold as merging
> Marvell PHY PTP support into mainline _will_ regress the superior PTP
> support on the Macchiatobin platform for the reasons outlined in:
> 
> https://lore.kernel.org/netdev/20200729220748.GW1605@shell.armlinux.org.uk/
> 
> Attempting to fix this problem was basically rejected by the PTP
> maintainer, and thus we're at a deadlock over the issue, and Marvell
> PHY PTP support can never be merged into mainline.

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?