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Subject: Re: [PATCH net-next 2/6] ARM: dts: ls1021a-tsn: 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>
 <20211013222313.3767605-3-vladimir.oltean@nxp.com>
From:   Florian Fainelli <f.fainelli@gmail.com>
Message-ID: <28551a3d-541e-8538-6a2f-110eeacd0500@gmail.com>
Date:   Fri, 15 Oct 2021 10:16:24 -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 not apply delays
> in any direction (mostly because the SJA1105T can't do that, so this
> board uses PCB traces). To preserve that but also silence the driver,
> use explicit delays of 0 ns. The delay information from the phy-mode is
> 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