netdev - Re: [PATCH devicetree 1/3] ARM: dts: imx6qp-prtwd3: update RGMII delays for sja1105 switch

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Message-ID: <20211020121404.GA2298@pengutronix.de>
Date:   Wed, 20 Oct 2021 14:14:04 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH devicetree 1/3] ARM: dts: imx6qp-prtwd3: update RGMII
 delays for sja1105 switch

On Wed, Oct 20, 2021 at 02:36:11PM +0300, 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@....com>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>

Reviewed-by: Oleksij Rempel <o.rempel@...gutronix.de> 

> ---
>  arch/arm/boot/dts/imx6qp-prtwd3.dts | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/imx6qp-prtwd3.dts b/arch/arm/boot/dts/imx6qp-prtwd3.dts
> index 7648e8a02000..cf6571cc4682 100644
> --- a/arch/arm/boot/dts/imx6qp-prtwd3.dts
> +++ b/arch/arm/boot/dts/imx6qp-prtwd3.dts
> @@ -178,6 +178,8 @@ port@4 {
>  				label = "cpu";
>  				ethernet = <&fec>;
>  				phy-mode = "rgmii-id";
> +				rx-internal-delay-ps = <2000>;
> +				tx-internal-delay-ps = <2000>;
>  
>  				fixed-link {
>  					speed = <100>;
> -- 
> 2.25.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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