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: <Z1wnFXlgEU84VX8F@shell.armlinux.org.uk>
Date: Fri, 13 Dec 2024 12:22:45 +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 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.

8<===
From: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Subject: [PATCH net-next] net: pcs: lynx: implement pcs_validate()

Implement .pcs_validate() to restrict the interfaces to those which the
Lynx PCS supports.

Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
 drivers/net/pcs/pcs-lynx.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/net/pcs/pcs-lynx.c b/drivers/net/pcs/pcs-lynx.c
index 767a8c0714ac..fd2e06dba92e 100644
--- a/drivers/net/pcs/pcs-lynx.c
+++ b/drivers/net/pcs/pcs-lynx.c
@@ -326,7 +326,22 @@ static void lynx_pcs_link_up(struct phylink_pcs *pcs, unsigned int neg_mode,
 	}
 }
 
+static int lynx_pcs_validate(struct phylink_pcs *pcs, unsigned long *supported,
+			     const struct phylink_link_state *state)
+{
+	if (state->interface != PHY_INTERFACE_MODE_SGMII &&
+	    state->interface != PHY_INTERFACE_MODE_QSGMII &&
+	    state->interface != PHY_INTERFACE_MODE_1000BASEX &&
+	    state->interface != PHY_INTERFACE_MODE_2500BASEX &&
+	    state->interface != PHY_INTERFACE_MODE_10GBASER &&
+	    state->interface != PHY_INTERFACE_MODE_USXGMII)
+		return -EINVAL;
+
+	return 0;
+}
+
 static const struct phylink_pcs_ops lynx_pcs_phylink_ops = {
+	.pcs_validate = lynx_pcs_validate,
 	.pcs_inband_caps = lynx_pcs_inband_caps,
 	.pcs_get_state = lynx_pcs_get_state,
 	.pcs_config = lynx_pcs_config,
-- 
2.30.2

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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