netdev - Re: [RFC PATCH net-next 7/9] net: dsa: microchip: ksz9477: add hardware time stamping support

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Message-ID: <20201022030217.GA2105@hoboy.vegasvil.org>
Date:   Wed, 21 Oct 2020 20:02:17 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Christian Eggers <ceggers@...i.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Helmut Grohne <helmut.grohne@...enta.de>,
        Paul Barker <pbarker@...sulko.com>,
        Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>,
        George McCollister <george.mccollister@...il.com>,
        Marek Vasut <marex@...x.de>,
        Tristram Ha <Tristram.Ha@...rochip.com>,
        "David S . Miller" <davem@...emloft.net>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net-next 7/9] net: dsa: microchip: ksz9477: add
 hardware time stamping support

On Thu, Oct 22, 2020 at 02:39:35AM +0300, Vladimir Oltean wrote:
> So how _does_ that work for TI PHYTER?
> 
> As far as we understand, the PHYTER appears to autonomously mangle PTP packets
> in the following way:
> - subtracting t2 on RX from the correctionField of the Pdelay_Req
> - adding t3 on TX to the correctionField of the Pdelay_Resp

The Phyter does not support peer-to-peer one step.

The only driver that implements it is ptp_ines.c.

And *that* driver/HW implements it correctly.

Thanks,
Richard