Merge branch 'phylink-resolve-fixes'

Marek Behún says:

====================
phylink resolve fixes

With information from me and my nagging, Russell has produced two fixes
for phylink, which add code that triggers another phylink_resolve() from
phylink_resolve(), if certain conditions are met:
  interface is being changed
or
  link is down and previous link was up
These are needed because sometimes the PCS callbacks may provide stale
values if link / speed / ...
====================

Link: https://lore.kernel.org/r/20211123154403.32051-1-kabel@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

drivers/net/phy/phylink.c

@@ -710,6 +710,7 @@ static void phylink_resolve(struct work_struct *w)
 	struct phylink_link_state link_state;
 	struct net_device *ndev = pl->netdev;
 	bool mac_config = false;
+	bool retrigger = false;
 	bool cur_link_state;
 
 	mutex_lock(&pl->state_mutex);
@@ -723,6 +724,7 @@ static void phylink_resolve(struct work_struct *w)
 		link_state.link = false;
 	} else if (pl->mac_link_dropped) {
 		link_state.link = false;
+		retrigger = true;
 	} else {
 		switch (pl->cur_link_an_mode) {
 		case MLO_AN_PHY:
@@ -739,6 +741,19 @@ static void phylink_resolve(struct work_struct *w)
 		case MLO_AN_INBAND:
 			phylink_mac_pcs_get_state(pl, &link_state);
 
+			/* The PCS may have a latching link-fail indicator.
+			 * If the link was up, bring the link down and
+			 * re-trigger the resolve. Otherwise, re-read the
+			 * PCS state to get the current status of the link.
+			 */
+			if (!link_state.link) {
+				if (cur_link_state)
+					retrigger = true;
+				else
+					phylink_mac_pcs_get_state(pl,
+								  &link_state);
+			}
+
 			/* If we have a phy, the "up" state is the union of
 			 * both the PHY and the MAC
 			 */
@@ -747,6 +762,15 @@ static void phylink_resolve(struct work_struct *w)
 
 			/* Only update if the PHY link is up */
 			if (pl->phydev && pl->phy_state.link) {
+				/* If the interface has changed, force a
+				 * link down event if the link isn't already
+				 * down, and re-resolve.
+				 */
+				if (link_state.interface !=
+				    pl->phy_state.interface) {
+					retrigger = true;
+					link_state.link = false;
+				}
 				link_state.interface = pl->phy_state.interface;
 
 				/* If we have a PHY, we need to update with
@@ -789,7 +813,7 @@ static void phylink_resolve(struct work_struct *w)
 		else
 			phylink_link_up(pl, link_state);
 	}
-	if (!link_state.link && pl->mac_link_dropped) {
+	if (!link_state.link && retrigger) {
 		pl->mac_link_dropped = false;
 		queue_work(system_power_efficient_wq, &pl->resolve);
 	}