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

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Message-ID: <ZAEU5BQQQHhvcW5P@hoboy.vegasvil.org>
Date:   Thu, 2 Mar 2023 13:28:04 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Köry Maincent <kory.maincent@...tlin.com>,
        andrew@...n.ch, davem@...emloft.net, f.fainelli@...il.com,
        hkallweit1@...il.com, netdev@...r.kernel.org,
        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, Mar 02, 2023 at 08:49:32AM -0800, Jakub Kicinski wrote:

> Don't wanna waste too much of your time with the questions since
> I haven't done much research but - wouldn't MAC timestamp be a better
> choice more often (as long as it's a real, to-spec PTP stamp)? 
> Are we picking PHY for historical reasons?

I think the default rating for MACs can be higher, but in the case of
at least one PHY, the TI PHYTER (dp83640), the PHY is the far better
choice.  This PHY surpasses any MAC on the market, and so it should
have a high rating.

For example, I've seen boards with the TI am335x, initially selected
because of the built in CPTS PTP feature, which the designers were
forced augment with the PHYTERs simply because of inadequate SoC
implementation.

In other words, if you find a board with the PHYTER, then it is there
for a reason.

Thanks,
Richard