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

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Message-ID: <ZnlxO2yAxkkkejU-@lore-desk>
Date: Mon, 24 Jun 2024 15:14:35 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Andrew Lunn <andrew@...n.ch>
Cc: 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,
	benjamin.larsson@...exis.eu, rkannoth@...vell.com,
	sgoutham@...vell.com
Subject: Re: [PATCH v3 net-next 2/2] net: airoha: Introduce ethernet support
 for EN7581 SoC

> > > > +static void airoha_fe_oq_rsv_init(struct airoha_eth *eth)
> > > > +{
> > > > +	int i;
> > > > +
> > > > +	/* hw misses PPE2 oq rsv */
> > > > +	airoha_fe_set(eth, REG_FE_PSE_BUF_SET,
> > > > +		      PSE_DEF_RSV_PAGE * PSE_PORT8_QUEUE);
> > > > +
> > > > +	for (i = 0; i < PSE_PORT0_QUEUE; i++)
> > > > +		airoha_fe_set_pse_oq_rsv(eth, 0, i, 0x40);
> > > > +	for (i = 0; i < PSE_PORT1_QUEUE; i++)
> > > > +		airoha_fe_set_pse_oq_rsv(eth, 1, i, 0x40);
> > > > +
> > > > +	for (i = 6; i < PSE_PORT2_QUEUE; i++)
> > > > +		airoha_fe_set_pse_oq_rsv(eth, 2, i, 0);
> > > > +
> > > > +	for (i = 0; i < PSE_PORT3_QUEUE; i++)
> > > > +		airoha_fe_set_pse_oq_rsv(eth, 3, i, 0x40);
> > > 
> > > 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?
> > 
> > airoha_eth driver implements just MAC features (FE and QDMA). Currently we only
> > support the connection to the DSA switch (GDM1). EN7581 SoC relies on mt7530 driver
> > for DSA (I have not posted the patch for mt7530 yet, I will do after airoha_eth
> > ones).
> > 
> > > 
> > > If there some open architecture documentation for this device?
> > > 
> > > What are these ports about?
> > 
> > airoha_fe_oq_rsv_init() (we can improve naming here :) is supposed to configure
> > hw pre-allocated memory for each queue available in Packet Switching Engine
> > (PSE) ports. PSE ports are not switch ports, but SoC internal ports used to
> > connect PSE to different modules. In particular, we are currently implementing
> > just the two connections below:
> > - CDM1 (port0) connects PSE to QDMA1
> > - GDM1 (port1) connects PSE to MT7530 DSA switch
> > 
> > In the future we will post support for GDM2, GDM3 and GDM4 ports that are
> > connecting PSE to exteranl PHY modules.
> 
> I've not looked at the datasheet yet, but maybe add some ASCII art
> diagram of the architecture in the commit message, or even a .rst file
> somewhere under Documentation. It is hard to get the big picture
> looking at just the code, and only the MAC driver without all the
> other parts.

ack, I will do my best :)

> 
> > > > +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?
> > 
> > The check above is used to support configuration where MT7530 DSA switch module
> > is not loaded (I tested this configuration removing the MT7530 DSA switch from
> > board dts and resetting the switch). Since for the moment we just support GDM1
> > port (PSE port connected to the switch) we can probably assume it is always the
> > case and remove this check. In the future we will need this configuration to support
> > GDM2 or GDM3 (PSE port connected to external phy modules). Do you prefer to
> > always set GDM1_STAG_EN_MASK for the moment?
> 
> If it will be needed, then keep it. But it is the sort of thing which
> raises questions, so its good to explain it, either in the commit
> message, or in the code.

ack, I will add it in v4

Regards,
Lorenzo

> 
> 	Andrew

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