net: phylink: ensure PHY momentary link-fails are handled

Normally, phylib won't notify changes in quick succession. However, as
a result of commit 3e43b903da04 ("net: phy: Immediately call
adjust_link if only tx_lpi_enabled changes") this is no longer true -
it is now possible that phy_link_down() and phy_link_up() will both
complete before phylink's resolver has run, which means it'll miss that
pl->phy_state.link momentarily became false.

Rename "mac_link_dropped" to be more generic "link_failed" since it will
cover more than the MAC/PCS end of the link failing, and arrange to set
this in phylink_phy_change() if we notice that the PHY reports that the
link is down.

This will ensure that we capture an EEE reconfiguration event.

Fixes: 3e43b903da04 ("net: phy: Immediately call adjust_link if only tx_lpi_enabled changes")
Signed-off-by: Russell King (Oracle) <[e-mail]>
Reviewed-by: Oleksij Rempel <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/phy/phylink.c

···
 	unsigned int pcs_neg_mode;
 	unsigned int pcs_state;
 
-	bool mac_link_dropped;
+	bool link_failed;
 	bool using_mac_select_pcs;
 
 	struct sfp_bus *sfp_bus;
···
 		cur_link_state = pl->old_link_state;
 
 	if (pl->phylink_disable_state) {
-		pl->mac_link_dropped = false;
+		pl->link_failed = false;
 		link_state.link = false;
-	} else if (pl->mac_link_dropped) {
+	} else if (pl->link_failed) {
 		link_state.link = false;
 		retrigger = true;
 	} else {
···
 			phylink_link_up(pl, link_state);
 	}
 	if (!link_state.link && retrigger) {
-		pl->mac_link_dropped = false;
+		pl->link_failed = false;
 		queue_work(system_power_efficient_wq, &pl->resolve);
 	}
 	mutex_unlock(&pl->state_mutex);
···
 		pl->phy_state.pause |= MLO_PAUSE_RX;
 	pl->phy_state.interface = phydev->interface;
 	pl->phy_state.link = up;
+	if (!up)
+		pl->link_failed = true;
 	mutex_unlock(&pl->state_mutex);
 
 	phylink_run_resolve(pl);
···
 static void phylink_link_changed(struct phylink *pl, bool up, const char *what)
 {
 	if (!up)
-		pl->mac_link_dropped = true;
+		pl->link_failed = true;
 	phylink_run_resolve(pl);
 	phylink_dbg(pl, "%s link %s\n", what, up ? "up" : "down");
 }
···
 	 * link will cycle.
 	 */
 	if (manual_changed) {
-		pl->mac_link_dropped = true;
+		pl->link_failed = true;
 		phylink_run_resolve(pl);
 	}