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Subject: Re: [PATCH net-next 1/6] ARM: dts: imx6qp-prtwd3: update RGMII delays
 for sja1105 switch
To:     Vladimir Oltean <vladimir.oltean@nxp.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org
Cc:     devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        Rob Herring <robh+dt@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>, Andrew Lunn <andrew@lunn.ch>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        Prasanna Vengateshan <prasanna.vengateshan@microchip.com>,
        Ansuel Smith <ansuelsmth@gmail.com>,
        =?UTF-8?Q?Alvin_=c5=a0ipraga?= <alsi@bang-olufsen.dk>
References: <20211013222313.3767605-1-vladimir.oltean@nxp.com>
 <20211013222313.3767605-2-vladimir.oltean@nxp.com>
From:   Florian Fainelli <f.fainelli@gmail.com>
Message-ID: <531b85ec-4227-85b5-f1c7-206f293ec0b9@gmail.com>
Date:   Fri, 15 Oct 2021 10:16:07 -0700
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On 10/13/21 3:23 PM, Vladimir Oltean wrote:
> In the new behavior, the sja1105 driver expects there to be explicit
> RGMII delays present on the fixed-link ports, otherwise it will complain
> that it falls back to legacy behavior, which is to apply RGMII delays
> incorrectly derived from the phy-mode string.
> 
> In this case, the legacy behavior of the driver is to apply both RX and
> TX delays. To preserve that, add explicit 2 nanosecond delays, which are
> identical with what the driver used to add (a 90 degree phase shift).
> The delays from the phy-mode are ignored by new kernels (it's still
> RGMII as long as it's "rgmii*" something), and the explicit
> {rx,tx}-internal-delay-ps properties are ignored by old kernels, so the
> change works both ways.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian