linux-kernel - Re: [PATCH net-next 4/6] arm64: dts: fsl: ls1028a: Add Felix switch port DT node

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Message-ID: <20190624115558.GA5690@piout.net>
Date:   Mon, 24 Jun 2019 13:55:58 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Claudiu Manoil <claudiu.manoil@....com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        "David S . Miller" <davem@...emloft.net>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexandru Marginean <alexandru.marginean@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Allan Nielsen <Allan.Nielsen@...rosemi.com>,
        Rob Herring <robh+dt@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH net-next 4/6] arm64: dts: fsl: ls1028a: Add Felix switch
 port DT node

On 24/06/2019 11:45:37+0000, Claudiu Manoil wrote:
> Hi Andrew,
> 
> >-----Original Message-----
> >From: Andrew Lunn <andrew@...n.ch>
> >Sent: Friday, June 21, 2019 7:50 PM
> >To: Claudiu Manoil <claudiu.manoil@....com>
> >Cc: David S . Miller <davem@...emloft.net>; devicetree@...r.kernel.org;
> >Alexandre Belloni <alexandre.belloni@...tlin.com>; netdev@...r.kernel.org;
> >Alexandru Marginean <alexandru.marginean@....com>; linux-
> >kernel@...r.kernel.org; UNGLinuxDriver@...rochip.com; Allan Nielsen
> ><Allan.Nielsen@...rosemi.com>; Rob Herring <robh+dt@...nel.org>; linux-
> >arm-kernel@...ts.infradead.org
> >Subject: Re: [PATCH net-next 4/6] arm64: dts: fsl: ls1028a: Add Felix switch port
> >DT node
> >
> >On Fri, Jun 21, 2019 at 06:38:50PM +0300, Claudiu Manoil wrote:
> >> The switch device features 6 ports, 4 with external links
> >> and 2 internally facing to the ls1028a SoC and connected via
> >> fixed links to 2 internal enetc ethernet controller ports.
> >
> >Hi Claudiu
> >
> >> +			switch@0,5 {
> >> +				compatible = "mscc,felix-switch";
> >> +				reg = <0x000500 0 0 0 0>;
> >> +
> >> +				ethernet-ports {
> >> +					#address-cells = <1>;
> >> +					#size-cells = <0>;
> >> +
> >> +					/* external ports */
> >> +					switch_port0: port@0 {
> >> +						reg = <0>;
> >> +					};
> >> +					switch_port1: port@1 {
> >> +						reg = <1>;
> >> +					};
> >> +					switch_port2: port@2 {
> >> +						reg = <2>;
> >> +					};
> >> +					switch_port3: port@3 {
> >> +						reg = <3>;
> >> +					};
> >> +					/* internal to-cpu ports */
> >> +					port@4 {
> >> +						reg = <4>;
> >> +						fixed-link {
> >> +							speed = <1000>;
> >> +							full-duplex;
> >> +						};
> >> +					};
> >> +					port@5 {
> >> +						reg = <5>;
> >> +						fixed-link {
> >> +							speed = <1000>;
> >> +							full-duplex;
> >> +						};
> >> +					};
> >> +				};
> >> +			};
> >
> >This sounds like a DSA setup, where you have SoC ports connected to
> >the switch. With DSA, the CPU ports of the switch are special. We
> >don't create netdev's for them, the binding explicitly list which SoC
> >interface they are bound to, etc.
> >
> >What model are you using here? I'm just trying to understand the setup
> >to ensure it is consistent with the swichdev model.
> >
> 
> Yeah, there are 2 ethernet controller ports (managed by the enetc driver) 
> connected inside the SoC via SGMII links to 2 of the switch ports, one of
> these switch ports can be configured as CPU port (with follow-up patches).
> 
> This configuration may look prettier on DSA, but the main restriction here
> is that the entire functionality is provided by the ocelot driver which is a
> switchdev driver.  I don't think it would be a good idea to copy-paste code
> from ocelot to a separate dsa driver.
> 

We should probably make the ocelot driver a DSA driver then...


-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com