netdev - Re: [PATCH v3 net-next 2/2] net: airoha: Introduce ethernet support for EN7581 SoC

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Date: Fri, 28 Jun 2024 13:11:48 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Andrew Lunn <andrew@...n.ch>
Cc: Benjamin Larsson <benjamin.larsson@...exis.eu>, netdev@...r.kernel.org,
	nbd@....name, lorenzo.bianconi83@...il.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	conor@...nel.org, linux-arm-kernel@...ts.infradead.org,
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, devicetree@...r.kernel.org,
	catalin.marinas@....com, will@...nel.org, upstream@...oha.com,
	angelogioacchino.delregno@...labora.com, rkannoth@...vell.com,
	sgoutham@...vell.com
Subject: Re: [PATCH v3 net-next 2/2] net: airoha: Introduce ethernet support
 for EN7581 SoC

> On Mon, Jun 24, 2024 at 01:01:44AM +0200, Benjamin Larsson wrote:
> > Hi,
> > > Code like this is making me wounder about the split between MAC
> > > driver, DSA driver and DSA tag driver. Or if it should actually be a
> > > pure switchdev driver?
> > > 
> > > If there some open architecture documentation for this device?
> > > 
> > > What are these ports about?
> > > 
> > > > +static int airoha_dev_open(struct net_device *dev)
> > > > +{
> > > > +	struct airoha_eth *eth = netdev_priv(dev);
> > > > +	int err;
> > > > +
> > > > +	if (netdev_uses_dsa(dev))
> > > > +		airoha_fe_set(eth, REG_GDM1_INGRESS_CFG, GDM1_STAG_EN_MASK);
> > > > +	else
> > > > +		airoha_fe_clear(eth, REG_GDM1_INGRESS_CFG, GDM1_STAG_EN_MASK);
> > > Does that imply both instances of the GMAC are not connected to the
> > > switch? Can one be used with a PHY?
> > > 
> > > 	Andrew
> > 
> > https://mirror2.openwrt.org/docs/MT7981B_Wi-Fi6_Platform_Datasheet_Open_V1.0.pdf
> > 
> > page 107 (text for 9.1.1 is relevant but not a complete match). In the
> > EN7581 case there is a 5 port switch in the place of GMAC1 (one switch port
> > is connected to GDM1).
> 
> The typical DSA architecture is that the SoC MAC is connected to a
> switch MAC port. You say here, the switch is directly connected to the
> GGM1. So there is no GMAC involved? If there is no MAC, you don't need
> a MAC driver.
> 
> It seems more likely there is a GMAC, and the SGMII interface, or
> something similar is connected to the switch?
> 
> 	Andrew
> 

The EN7581 architecture is similar to MT7988a one. There is a MAC port (GDM1) 
connected to a MT7530 DSA switch. With 'directly connected', I think Benjamin
means we rely on the switch internal PHYs for GDM1. Moreover the SoC supports
other MAC ports (GDM2, GDM3, GDM4) that can be connected to extanl PHYs.
In v4 I will rework the driver adding the capability to plug even GDM{2,3,4}.

Regards,
Lorenzo

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