netdev - [PATCH RFC net-next 04/13] net: phylink: ensure link is down when changing interface

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Message-Id: <E1jqHFj-0006Og-5E@rmk-PC.armlinux.org.uk>
Date:   Tue, 30 Jun 2020 15:28:51 +0100
From:   Russell King <rmk+kernel@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Ioana Ciornei <ioana.ciornei@....com>
Cc:     Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandru Marginean <alexandru.marginean@....com>,
        "michael@...le.cc" <michael@...le.cc>,
        "olteanv@...il.com" <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH RFC net-next 04/13] net: phylink: ensure link is down when
 changing interface

The only PHYs that are used with phylink which change their interface
are the BCM84881 and MV88X3310 family, both of which only change their
interface modes on link-up events.  However, rather than relying upon
this behaviour by the PHY, we should give a stronger guarantee when
resolving that the link will be down whenever we change the interface
mode.  This patch implements that stronger guarantee for resolve.

Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
---
 drivers/net/phy/phylink.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 8ffe5df5c296..1507ea8a9385 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -620,8 +620,18 @@ static void phylink_resolve(struct work_struct *w)
 		}
 	}
 
-	if (mac_config)
+	if (mac_config) {
+		if (link_state.interface != pl->link_config.interface) {
+			/* The interface has changed, force the link down and
+			 * then reconfigure.
+			 */
+			if (cur_link_state) {
+				phylink_link_down(pl);
+				cur_link_state = false;
+			}
+		}
 		phylink_mac_config(pl, &link_state);
+	}
 
 	if (link_state.link != cur_link_state) {
 		pl->old_link_state = link_state.link;
-- 
2.20.1