Re: [RFC 0/4] net: l2switch: Provide support for L2 switch on i.MX28 SoC

From: Lukasz Majewski <lukma@denx.de>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Peng Fan <peng.fan@nxp.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Fugang Duan <fugang.duan@nxp.com>,
	Shawn Guo <shawnguo@kernel.org>,
	stefan.agner@toradex.com, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, krzk@kernel.org,
	Vivien Didelot <vivien.didelot@gmail.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Vladimir Oltean <olteanv@gmail.com>,
	Fabio Estevam <festevam@gmail.com>,
	"David S . Miller" <davem@davemloft.net>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC 0/4] net: l2switch: Provide support for L2 switch on i.MX28 SoC
Date: Fri, 27 Nov 2020 10:16:15 +0100	[thread overview]
Message-ID: <20201127101615.7349b35f@jawa> (raw)
In-Reply-To: <20201127005502.GQ2075216@lunn.ch>

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Hi Andrew,

> > (A side question - DSA uses switchdev, so when one shall use
> > switchdev standalone?)  
> 
> DSA gives you a framework for an Ethernet switch connected to a host
> via Ethernet for the data plane. Generally, that Ethernet link to the
> switch is a MAC to MAC connection. It can be PHY to PHY. But those are
> just details. The important thing is you use an Ethernet driver on the
> host.
> 
> If you look at pure switchdev devices, they generally DMA frames
> directly into the switch. There is either one DMA queue per switch
> port, or there is a way to multiplex frames over one DMA queue,
> generally by additional fields in the buffer descriptor.
> 
> For this device, at the moment, it is hard to say which is the best
> fit. A lot will depend on how the FEC driver works, if you can reuse
> it, while still having the degree of control you need over the DMA
> channel. If you can reuse the FEC driver, then a DSA driver might
> work. If the coupling it too loose, and you have to take control of
> the DMA, then a pure switchdev driver seems more appropriate.
> 
>     Andrew
> 

Thanks for the detailed explanation.

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
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