net: phylink: add pcs_query_inband()

Add a pcs_query_inband() interface which reflects phy_query_inband()
for PHYs. This can be used to determine for the specified interface
mode whether in-band signalling is supported by the PCS, and whether
the PCS requires in-band signalling.

This is used to determine whether we should use inband autonegotiation
in inband mode, which may be required or may be unsupported in various
interface modes.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

2 files changed, 176 insertions, 21 deletions

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index e96eded31e4c..b526488a84cc 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -980,6 +980,15 @@ static void phylink_resolve_an_pause(struct phylink_link_state *state)
 	}
 }
 
+static unsigned int phylink_pcs_query_inband(struct phylink_pcs *pcs,
+				    phy_interface_t interface)
+{
+	if (pcs && pcs->ops->pcs_query_inband)
+		return pcs->ops->pcs_query_inband(pcs, interface);
+
+	return 0;
+}
+
 static void phylink_pcs_pre_config(struct phylink_pcs *pcs,
 				   phy_interface_t interface)
 {
@@ -1079,6 +1088,8 @@ static void phylink_pcs_an_restart(struct phylink *pl)
 
 /**
  * phylink_pcs_neg_mode() - helper to determine PCS inband mode
+ * @pl: a pointer to a &struct phylink returned from phylink_create()
+ * @pcs: a pointer to &struct phylink_pcs
  * @mode: one of %MLO_AN_FIXED, %MLO_AN_PHY, %MLO_AN_INBAND.
  * @interface: interface mode to be used
  * @advertising: adertisement ethtool link mode mask
@@ -1096,11 +1107,19 @@ static void phylink_pcs_an_restart(struct phylink *pl)
  * Note: this is for cases where the PCS itself is involved in negotiation
  * (e.g. Clause 37, SGMII and similar) not Clause 73.
  */
-static unsigned int phylink_pcs_neg_mode(unsigned int mode,
+static unsigned int phylink_pcs_neg_mode(struct phylink *pl,
+					 struct phylink_pcs *pcs,
+					 unsigned int mode,
 					 phy_interface_t interface,
 					 const unsigned long *advertising)
 {
+	unsigned int phy_link_mode = 0;
+	unsigned int pcs_link_mode;
 	unsigned int neg_mode;
+	enum {
+		INBAND_CISCO_SGMII,
+		INBAND_8023Z,
+	} type;
 
 	switch (interface) {
 	case PHY_INTERFACE_MODE_SGMII:
@@ -1112,10 +1131,7 @@ static unsigned int phylink_pcs_neg_mode(unsigned int mode,
 		 * inband communication. Note: there exist PHYs that run
 		 * with SGMII but do not send the inband data.
 		 */
-		if (!phylink_autoneg_inband(mode))
-			neg_mode = PHYLINK_PCS_NEG_OUTBAND;
-		else
-			neg_mode = PHYLINK_PCS_NEG_INBAND_ENABLED;
+		type = INBAND_CISCO_SGMII;
 		break;
 
 	case PHY_INTERFACE_MODE_1000BASEX:
@@ -1126,20 +1142,92 @@ static unsigned int phylink_pcs_neg_mode(unsigned int mode,
 		 * as well, but drivers may not support this, so may
 		 * need to override this.
 		 */
-		if (!phylink_autoneg_inband(mode))
-			neg_mode = PHYLINK_PCS_NEG_OUTBAND;
-		else if (linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
-					   advertising))
-			neg_mode = PHYLINK_PCS_NEG_INBAND_ENABLED;
-		else
-			neg_mode = PHYLINK_PCS_NEG_INBAND_DISABLED;
+		type = INBAND_8023Z;
 		break;
 
 	default:
-		neg_mode = PHYLINK_PCS_NEG_NONE;
-		break;
+		return PHYLINK_PCS_NEG_NONE;
 	}
 
+	pcs_link_mode = phylink_pcs_query_inband(pcs, interface);
+	if (pl->phydev)
+		phy_link_mode = phy_query_inband(pl->phydev, interface);
+
+	if (!phylink_autoneg_inband(mode)) {
+		/* If either the PCS or PHY requires inband to be enabled,
+		 * this is an invalid configuration. Provide a diagnostic
+		 * message for this case, but don't try to force the issue.
+		 */
+		if ((pcs_link_mode | phy_link_mode) & LINK_INBAND_REQUIRED) {
+			const char *s1, *s2, *s3, *empty = "";
+
+			s1 = s2 = s3 = empty;
+			if (pcs_link_mode & LINK_INBAND_REQUIRED)
+				s1 = "PCS";
+
+			if (phy_link_mode & LINK_INBAND_REQUIRED)
+				s3 = "PHY";
+
+			if (s1 != empty && s3 != empty)
+				s2 = " and ";
+
+			phylink_warn(pl,
+				     "firmware wants %s mode, but %s%s%s requires inband\n",
+				     phylink_an_mode_str(mode),
+				     s1, s2, s3);
+		}
+		return PHYLINK_PCS_NEG_OUTBAND;
+	}
+
+	/* For SGMII modes, which are designed to be used with PHYs, we
+	 * try to use inband mode where-ever possible.
+	 */
+	if (type == INBAND_CISCO_SGMII) {
+		/* If the PCS or PHY can not provide inband, then use
+		 * out of band.
+		 */
+		if (pcs_link_mode == LINK_INBAND_VALID ||
+		    phy_link_mode == LINK_INBAND_VALID) {
+			/* If either require inband, then we have a conflict. */
+			return PHYLINK_PCS_NEG_OUTBAND;
+		}
+
+		/* Otherwise, use inband as this is what was requested.
+		 * This covers the case where the supported inband modes
+		 * have not been provided, or the PCS and PHY report that
+		 * they support inband.
+		 */
+		return PHYLINK_PCS_NEG_INBAND_ENABLED;
+	}
+
+	/* For 802.3z, handle the PHY present vs absent cases separately */
+	if (!pl->phydev) {
+		/* PHY absent: always use inband but inband may be disabled */
+		/* If the PCS doesn't support inband, then inband must be
+		 * disabled.
+		 */
+		if (pcs_link_mode == LINK_INBAND_VALID)
+			return PHYLINK_PCS_NEG_INBAND_DISABLED;
+
+		/* If the PCS requires inband, then inband must always be
+		 * enabled.
+		 */
+		if (pcs_link_mode & LINK_INBAND_REQUIRED)
+			return PHYLINK_PCS_NEG_INBAND_ENABLED;
+
+		/* For the possible case, fall through to the "legacy" code. */
+	} else {
+		/* PHY present, inband mode depends on the capabilities
+		 * of both.
+		 */
+	}
+
+	/* Legacy, so determine inband depending on the advertising bit */
+	if (linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, advertising))
+		neg_mode = PHYLINK_PCS_NEG_INBAND_ENABLED;
+	else
+		neg_mode = PHYLINK_PCS_NEG_INBAND_DISABLED;
+
 	return neg_mode;
 }
 
@@ -1154,10 +1242,6 @@ static void phylink_major_config(struct phylink *pl, bool restart,
 
 	phylink_dbg(pl, "major config %s\n", phy_modes(state->interface));
 
-	pl->pcs_neg_mode = phylink_pcs_neg_mode(pl->cur_link_an_mode,
-						state->interface,
-						state->advertising);
-
 	if (pl->using_mac_select_pcs) {
 		pcs = pl->mac_ops->mac_select_pcs(pl->config, state->interface);
 		if (IS_ERR(pcs)) {
@@ -1170,6 +1254,11 @@ static void phylink_major_config(struct phylink *pl, bool restart,
 		pcs_changed = pcs && pl->pcs != pcs;
 	}
 
+	pl->pcs_neg_mode = phylink_pcs_neg_mode(pl, pcs,
+						pl->cur_link_an_mode,
+						state->interface,
+						state->advertising);
+
 	phylink_pcs_poll_stop(pl);
 
 	if (pl->mac_ops->mac_prepare) {
@@ -1260,9 +1349,10 @@ static int phylink_change_inband_advert(struct phylink *pl)
 		    pl->link_config.pause);
 
 	/* Recompute the PCS neg mode */
-	pl->pcs_neg_mode = phylink_pcs_neg_mode(pl->cur_link_an_mode,
-					pl->link_config.interface,
-					pl->link_config.advertising);
+	pl->pcs_neg_mode = phylink_pcs_neg_mode(pl, pl->pcs,
+						pl->cur_link_an_mode,
+						pl->link_config.interface,
+						pl->link_config.advertising);
 
 	neg_mode = pl->cur_link_an_mode;
 	if (pl->pcs->neg_mode)
@@ -2520,6 +2610,39 @@ int phylink_ethtool_ksettings_get(struct phylink *pl,
 }
 EXPORT_SYMBOL_GPL(phylink_ethtool_ksettings_get);
 
+static int phylink_query_inband(struct phylink *pl, phy_interface_t interface)
+{
+	struct phylink_pcs *pcs;
+
+	if (!pl->using_mac_select_pcs)
+		return 0;
+
+	pcs = pl->mac_ops->mac_select_pcs(pl->config, interface);
+	if (!pcs)
+		return 0;
+
+	return phylink_pcs_query_inband(pcs, interface);
+}
+
+static bool phylink_validate_pcs_an(struct phylink *pl,
+				    phy_interface_t interface, bool an_state)
+{
+	int link_inband = phylink_query_inband(pl, interface);
+
+	/* If the PCS doesn't implement inband support, be permissive. */
+	if (!(link_inband & LINK_INBAND_VALID))
+		return true;
+
+	/* If the PCS can configure the use of inband, allow either state */
+	if (link_inband & LINK_INBAND_POSSIBLE)
+		return true;
+
+	/* Otherwise, require the AN state to be fixed according to the
+	 * required flag.
+	 */
+	return an_state == !!(link_inband & LINK_INBAND_REQUIRED);
+}
+
 /**
  * phylink_ethtool_ksettings_set() - set the link settings
  * @pl: a pointer to a &struct phylink returned from phylink_create()
@@ -2655,6 +2778,14 @@ 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_an(pl, config.interface,
+				     linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
+						       config.advertising)))
+		return -EINVAL;
+
 	mutex_lock(&pl->state_mutex);
 	pl->link_config.speed = config.speed;
 	pl->link_config.duplex = config.duplex;
@@ -3393,6 +3524,13 @@ 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_an(pl, interface,
+				     linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
+						       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 */
diff --git a/include/linux/phylink.h b/include/linux/phylink.h
index e1fa495c6f70..924cfdcc73f2 100644
--- a/include/linux/phylink.h
+++ b/include/linux/phylink.h
@@ -445,6 +445,7 @@ struct phylink_pcs {
 /**
  * struct phylink_pcs_ops - MAC PCS operations structure.
  * @pcs_validate: validate the link configuration.
+ * @pcs_query_inband: query inband support for interface mode.
  * @pcs_enable: enable the PCS.
  * @pcs_disable: disable the PCS.
  * @pcs_pre_config: pre-mac_config method (for errata)
@@ -458,6 +459,8 @@ struct phylink_pcs {
 struct phylink_pcs_ops {
 	int (*pcs_validate)(struct phylink_pcs *pcs, unsigned long *supported,
 			    const struct phylink_link_state *state);
+	unsigned int (*pcs_query_inband)(struct phylink_pcs *pcs,
+					 phy_interface_t interface);
 	int (*pcs_enable)(struct phylink_pcs *pcs);
 	void (*pcs_disable)(struct phylink_pcs *pcs);
 	void (*pcs_pre_config)(struct phylink_pcs *pcs,
@@ -494,6 +497,20 @@ int pcs_validate(struct phylink_pcs *pcs, unsigned long *supported,
 		 const struct phylink_link_state *state);
 
 /**
+ * pcs_query_inband - query inband support for interface mode.
+ * @pcs: a pointer to a &struct phylink_pcs.
+ * @interface: interface mode to be queried
+ *
+ * Returns zero if it is unknown what in-band signalling is supported by the
+ * PHY (e.g. because the PHY driver doesn't implement the method.) Otherwise,
+ * returns a bit mask of the LINK_INBAND_* values from
+ * &enum link_inband_signalling to describe which inband modes are supported
+ * for this interface mode.
+ */
+unsigned int pcs_query_inband(struct phylink_pcs *pcs,
+			      phy_interface_t interface);
+
+/**
  * pcs_enable() - enable the PCS.
  * @pcs: a pointer to a &struct phylink_pcs.
  */