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: <Z1yJQikqneoFNJT4@shell.armlinux.org.uk>
Date: Fri, 13 Dec 2024 19:21:38 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
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

On Fri, Dec 13, 2024 at 06:29:04PM +0100, Maxime Chevallier wrote:
> 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 :)

I've actually already created that series!

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