__igc_resume() calls netif_device_attach() only inside the
netif_running() branch, so an interface that was down during suspend
is never re-attached on resume. It then stays in the not-present state
that __igc_shutdown() set via netif_device_detach(): ethtool reports
ENODEV and every attempt to bring the interface up fails the
netif_device_present() check in __dev_open() with -ENODEV, silently,
since __igc_resume() returns 0. Only reloading the driver recovers the
device.

This is easy to hit in practice because NetworkManager brings managed
interfaces down before sleep unless Wake-on-LAN is configured, making
the adapter unusable after every suspend/resume cycle with WoL
disabled.

Re-attach the netdev on every successful resume, as igb and e1000e do.

Fixes: 6f31d6b643a3 ("igc: Refactor runtime power management flow")
Cc: stable@vger.kernel.org
Signed-off-by: Philipp David <redacted>
---
 drivers/net/ethernet/intel/igc/igc_main.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 2c9e2dfd8499..e777c2df0b73 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c

@@ -7586,11 +7586,13 @@ static int __igc_resume(struct device *dev, bool rpm)
 		err = __igc_open(netdev, true);
 		if (!rpm)
 			rtnl_unlock();
-		if (!err)
-			netif_device_attach(netdev);
+		if (err)
+			return err;
 	}
 
-	return err;
+	netif_device_attach(netdev);
+
+	return 0;
 }
 
 static int igc_resume(struct device *dev)

-- 
2.54.0