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

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Date:   Wed, 29 Jul 2020 06:19:32 -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

On Wed, Jul 29, 2020 at 11:58:07AM +0100, Russell King - ARM Linux admin wrote:
> How do we deal with this situation - from what I can see from the
> ethtool API, we have to make a choice about which to use.  How do we
> make that choice?

Unfortunately the stack does not implement simultaneous MAC + PHY time
stamping.  If your board has both, then you make the choice to use the
PHY by selecting NETWORK_PHY_TIMESTAMPING at kernel compile time.

(Also some MAC drivers do not defer to the PHY properly.  Sometimes
you can work around that by de-selecting the MAC's PTP function in the
Kconfig if possible, but otherwise you need to patch the MAC driver.)

> Do we need a property to indicate whether we wish to use the PHY
> or MAC PTP stamping, or something more elaborate?

To do this at run time would require quite some work, I expect.

Thanks,
Richard