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

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Date:   Mon, 24 Jun 2019 11:45:37 +0000
From:   Claudiu Manoil <claudiu.manoil@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "David S . Miller" <davem@...emloft.net>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "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

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.

Thanks for the review.
Claudiu