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Date:   Wed, 22 Apr 2020 15:39:21 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Oleksij Rempel <o.rempel@pengutronix.de>
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        David Jander <david@protonic.nl>,
        "David S. Miller" <davem@davemloft.net>, kernel@pengutronix.de,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        Philippe Schenker <philippe.schenker@toradex.com>,
        Russell King <linux@armlinux.org.uk>
Subject: Re: [PATCH net-next v3] net: phy: micrel: add phy-mode support for
 the KSZ9031 PHY
Message-ID: <20200422133921.GA974925@lunn.ch>
References: <20200422072137.8517-1-o.rempel@pengutronix.de>
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On Wed, Apr 22, 2020 at 09:21:37AM +0200, Oleksij Rempel wrote:
> Add support for following phy-modes: rgmii, rgmii-id, rgmii-txid, rgmii-rxid.
> 
> This PHY has an internal RX delay of 1.2ns and no delay for TX.
> 
> The pad skew registers allow to set the total TX delay to max 1.38ns and
> the total RX delay to max of 2.58ns (configurable 1.38ns + build in
> 1.2ns) and a minimal delay of 0ns.
> 
> According to the RGMII v1.3 specification the delay provided by PCB traces
> should be between 1.5ns and 2.0ns. The RGMII v2.0 allows to provide this
> delay by MAC or PHY. So, we configure this PHY to the best values we can
> get by this HW: TX delay to 1.38ns (max supported value) and RX delay to
> 1.80ns (best calculated delay)
> 
> The phy-modes can still be fine tuned/overwritten by *-skew-ps
> device tree properties described in:
> Documentation/devicetree/bindings/net/micrel-ksz90x1.txt
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew