linux-kernel - Re: [PATCH net-next 2/2] net: stmmac: dwmac-socfpga: Set interface modes from Lynx PCS as supported

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Message-ID: <20241213182904.55eb2504@fedora.home>
Date: Fri, 13 Dec 2024 18:29:04 +0100
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>, Jose Abreu
 <joabreu@...opsys.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 davem@...emloft.net, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Maxime Coquelin
 <mcoquelin.stm32@...il.com>, Alexis Lothoré
 <alexis.lothore@...tlin.com>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] net: stmmac: dwmac-socfpga: Set interface
 modes from Lynx PCS as supported

Hi Russell,

On Fri, 13 Dec 2024 12:22:45 +0000
"Russell King (Oracle)" <linux@...linux.org.uk> wrote:

> On Fri, Dec 13, 2024 at 10:05:25AM +0100, Maxime Chevallier wrote:
> > On Socfpga, the dwmac controller uses a variation of the Lynx PCS to get
> > additional support for SGMII and 1000BaseX. The switch between these
> > modes may occur at runtime (e.g. when the interface is wired to an SFP
> > cage). In such case, phylink will validate the newly selected interface
> > between the MAC and SFP based on the internal "supported_interfaces"
> > field.
> > 
> > For now in stmmac, this field is populated based on :
> >  - The interface specified in firmware (DT)
> >  - The interfaces supported by XPCS, when XPCS is in use.
> > 
> > In our case, the PCS in Lynx and not XPCS.
> > 
> > This commit makes so that the .pcs_init() implementation of
> > dwmac-socfpga populates the supported_interface when the Lynx PCS was
> > successfully initialized.  
> 
> I think it would also be worth adding this to Lynx, so phylink also
> gets to know (via its validation) which PHY interface modes the PCS
> can support.
> 
> However, maybe at this point we need to introduce an interface bitmap
> into struct phylink_pcs so that these kinds of checks can be done in
> phylink itself when it has the PCS, and it would also mean that stmmac
> could do something like:
> 
> 	struct phylink_pcs *pcs;
> 
> 	if (priv->hw->xpcs)
> 		pcs = xpcs_to_phylink_pcs(priv->hw->xpcs);
> 	else
> 		pcs = priv->hw->phylink_pcs;
> 
> 	if (pcs)
> 		phy_interface_or(priv->phylink_config.supported_interfaces,
> 				 priv->phylink_config.supported_interfaces,
> 				 pcs->supported_interfaces);
> 
> and not have to worry about this from individual PCS or platform code.

I like the idea, I will give it a go and send a series for that if
that's ok :)

Thanks,

Maxime