linux-kernel - Re: [RFC 2/3] net: Provide switchdev driver for NXP's More Than IP L2 switch

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Date:   Mon, 28 Jun 2021 14:05:26 +0200
From:   Lukasz Majewski <lukma@...x.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>, netdev@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Mark Einon <mark.einon@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/3] net: Provide switchdev driver for NXP's More Than IP
 L2 switch

Hi Andrew,

> > I do believe that I can just extend the L2 switch driver (fec_mtip.c
> > file to be precise) to provide full blown L2 switch functionality
> > without touching the legacy FEC more than in this patch set.
> > 
> > Would you consider applying this patch series then?  
> 
> What is most important is the ABI. If something is merged now, we need
> to ensure it does not block later refactoring to a clean new
> driver. The DT binding is considered ABI. So the DT binding needs to
> be like a traditional switchdev driver. Florian already pointed out,
> you can use a binding very similar to DSA. ti,cpsw-switch.yaml is
> another good example.

The best I could get would be:

&eth_switch {
	compatible = "imx,mtip-l2switch";
	reg = <0x800f8000 0x400>, <0x800fC000 0x4000>;

	interrupts = <100>;
	status = "okay";

	ethernet-ports {
		port1@1 {
			reg = <1>;
			label = "eth0";
			phys = <&mac0 0>;
		};

		port2@2 {
			reg = <2>;
			label = "eth1";
			phys = <&mac1 1>;
		};
	};
};

Which would abuse the "phys" properties usages - as 'mac[01]' are
referring to ethernet controllers.

On TI SoCs (e.g. am33xx-l4.dtsi) phys refer to some separate driver
responsible for PHY management. On NXP this is integrated with FEC
driver itself.

> 
> So before considering merging your changes, i would like to see a
> usable binding.
> 
> I also don't remember seeing support for STP. Without that, your
> network has broadcast storm problems when there are loops. So i would
> like to see the code needed to put ports into blocking, listening,
> learning, and forwarding states.
> 
> 	  Andrew




Best regards,

Lukasz Majewski

--

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