net: phylink: add function to resolve clause 73 negotiation

Add a function to resolve clause 73 negotiation according to the
priority resolution function described in clause 73.3.6.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/phylink.c

@@ -3212,6 +3212,45 @@ static const struct sfp_upstream_ops sfp_phylink_ops = {
 
 /* Helpers for MAC drivers */
 
+static struct {
+	int bit;
+	int speed;
+} phylink_c73_priority_resolution[] = {
+	{ ETHTOOL_LINK_MODE_100000baseCR4_Full_BIT, SPEED_100000 },
+	{ ETHTOOL_LINK_MODE_100000baseKR4_Full_BIT, SPEED_100000 },
+	/* 100GBASE-KP4 and 100GBASE-CR10 not supported */
+	{ ETHTOOL_LINK_MODE_40000baseCR4_Full_BIT, SPEED_40000 },
+	{ ETHTOOL_LINK_MODE_40000baseKR4_Full_BIT, SPEED_40000 },
+	{ ETHTOOL_LINK_MODE_10000baseKR_Full_BIT, SPEED_10000 },
+	{ ETHTOOL_LINK_MODE_10000baseKX4_Full_BIT, SPEED_10000 },
+	/* 5GBASE-KR not supported */
+	{ ETHTOOL_LINK_MODE_2500baseX_Full_BIT, SPEED_2500 },
+	{ ETHTOOL_LINK_MODE_1000baseKX_Full_BIT, SPEED_1000 },
+};
+
+void phylink_resolve_c73(struct phylink_link_state *state)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(phylink_c73_priority_resolution); i++) {
+		int bit = phylink_c73_priority_resolution[i].bit;
+		if (linkmode_test_bit(bit, state->advertising) &&
+		    linkmode_test_bit(bit, state->lp_advertising))
+			break;
+	}
+
+	if (i < ARRAY_SIZE(phylink_c73_priority_resolution)) {
+		state->speed = phylink_c73_priority_resolution[i].speed;
+		state->duplex = DUPLEX_FULL;
+	} else {
+		/* negotiation failure */
+		state->link = false;
+	}
+
+	phylink_resolve_an_pause(state);
+}
+EXPORT_SYMBOL_GPL(phylink_resolve_c73);
+
 static void phylink_decode_c37_word(struct phylink_link_state *state,
 				    uint16_t config_reg, int speed)
 {

include/linux/phylink.h

@@ -656,6 +656,8 @@ int phylink_mii_c22_pcs_config(struct mdio_device *pcs, unsigned int mode,
 			       const unsigned long *advertising);
 void phylink_mii_c22_pcs_an_restart(struct mdio_device *pcs);
 
+void phylink_resolve_c73(struct phylink_link_state *state);
+
 void phylink_mii_c45_pcs_get_state(struct mdio_device *pcs,
 				   struct phylink_link_state *state);