net: phylink: add pcs_inband_caps() method

Add a pcs_inband_caps() method to query the PCS for its inband link
capabilities, and use this to determine whether link modes used with
optical SFPs can be supported.

When a PCS does not provide a method, we allow inband negotiation to
be either on or off, making this a no-op until the pcs_inband_caps()
method is implemented by a PCS driver.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tIUs4-006IUU-7K@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 60 insertions, 0 deletions

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index fda53dd58285..42f3c7ccbf38 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -990,6 +990,15 @@ static void phylink_resolve_an_pause(struct phylink_link_state *state)
 	}
 }
 
+static unsigned int phylink_pcs_inband_caps(struct phylink_pcs *pcs,
+				    phy_interface_t interface)
+{
+	if (pcs && pcs->ops->pcs_inband_caps)
+		return pcs->ops->pcs_inband_caps(pcs, interface);
+
+	return 0;
+}
+
 static void phylink_pcs_pre_config(struct phylink_pcs *pcs,
 				   phy_interface_t interface)
 {
@@ -1043,6 +1052,24 @@ static void phylink_pcs_link_up(struct phylink_pcs *pcs, unsigned int neg_mode,
 		pcs->ops->pcs_link_up(pcs, neg_mode, interface, speed, duplex);
 }
 
+/* Query inband for a specific interface mode, asking the MAC for the
+ * PCS which will be used to handle the interface mode.
+ */
+static unsigned int phylink_inband_caps(struct phylink *pl,
+					 phy_interface_t interface)
+{
+	struct phylink_pcs *pcs;
+
+	if (!pl->mac_ops->mac_select_pcs)
+		return 0;
+
+	pcs = pl->mac_ops->mac_select_pcs(pl->config, interface);
+	if (!pcs)
+		return 0;
+
+	return phylink_pcs_inband_caps(pcs, interface);
+}
+
 static void phylink_pcs_poll_stop(struct phylink *pl)
 {
 	if (pl->cfg_link_an_mode == MLO_AN_INBAND)
@@ -2532,6 +2559,26 @@ int phylink_ethtool_ksettings_get(struct phylink *pl,
 }
 EXPORT_SYMBOL_GPL(phylink_ethtool_ksettings_get);
 
+static bool phylink_validate_pcs_inband_autoneg(struct phylink *pl,
+					        phy_interface_t interface,
+						unsigned long *adv)
+{
+	unsigned int inband = phylink_inband_caps(pl, interface);
+	unsigned int mask;
+
+	/* If the PCS doesn't implement inband support, be permissive. */
+	if (!inband)
+		return true;
+
+	if (linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, adv))
+		mask = LINK_INBAND_ENABLE;
+	else
+		mask = LINK_INBAND_DISABLE;
+
+	/* Check whether the PCS implements the required mode */
+	return !!(inband & mask);
+}
+
 /**
  * phylink_ethtool_ksettings_set() - set the link settings
  * @pl: a pointer to a &struct phylink returned from phylink_create()
@@ -2662,6 +2709,13 @@ int phylink_ethtool_ksettings_set(struct phylink *pl,
 	    phylink_is_empty_linkmode(config.advertising))
 		return -EINVAL;
 
+	/* Validate the autonegotiation state. We don't have a PHY in this
+	 * situation, so the PCS is the media-facing entity.
+	 */
+	if (!phylink_validate_pcs_inband_autoneg(pl, config.interface,
+						 config.advertising))
+		return -EINVAL;
+
 	mutex_lock(&pl->state_mutex);
 	pl->link_config.speed = config.speed;
 	pl->link_config.duplex = config.duplex;
@@ -3341,6 +3395,12 @@ static int phylink_sfp_config_optical(struct phylink *pl)
 	phylink_dbg(pl, "optical SFP: chosen %s interface\n",
 		    phy_modes(interface));
 
+	if (!phylink_validate_pcs_inband_autoneg(pl, interface,
+						 config.advertising)) {
+		phylink_err(pl, "autoneg setting not compatible with PCS");
+		return -EINVAL;
+	}
+
 	config.interface = interface;
 
 	/* Ignore errors if we're expecting a PHY to attach later */