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

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Message-ID: <20190624182614.GC5690@piout.net>
Date:   Mon, 24 Jun 2019 20:26:14 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "Allan W. Nielsen" <allan.nielsen@...rochip.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        "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 18:24:31+0200, Andrew Lunn wrote:
> On Mon, Jun 24, 2019 at 05:23:45PM +0200, Allan W. Nielsen wrote:
> > Hi Andrew,
> > 
> > The 06/24/2019 16:26, Andrew Lunn wrote:
> > > > > 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...
> > > An important part of DSA is being able to direct frames out specific
> > > ports when they ingress via the CPU port. Does the silicon support
> > > this? At the moment, i think it is using polled IO.
> > 
> > That is supported, it requires a bit of initial configuration of the Chip, but
> > nothing big (I believe this configuration is part of Claudiu's change-set).
> > 
> > But how do you envision this done?
> > 
> > - Let the existing SwitchDev driver and the DSA driver use a set of common
> >   functions.
> > - Convert the existing Ocelot driver from SwitchDev to DSA
> > - Fork (copy) the existing driver of Ocelot, and modify it as needed for the
> >   Felix driver
> > 
> > My guess is the first one, but I would like to understand what you have in mind.
> 
> I don't know the various architectures the switch is used in. But it
> does seem like a core library, and then a switchdev wrapper for Ocelot
> and a DSA wrapper for Felix would make sense.

Ocelot could also be used in a DSA setting where one port can be
connected to an external MAC and be used to inject/extract frames
to/from any other ports. In that case, the IFH would serve as the DSA
tag.


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