[PATCH 6.12.y] igc: fix netdev not re-attached after resume if interface is down

__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: [email protected]
Signed-off-by: Philipp David <[email protected]>
Reviewed-by: Aleksandr Loktionov <[email protected]>
Reviewed-by: Dima Ruinskiy <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
(cherry picked from commit b0ce5fd9fabe7c79463cf4602217d4dfeff5b1fd)
---
Conflict resolved cleanly using mergiraf. Backport tested on I225-V
hardware, suspend with WoL and suspend without WoL both bringing up
interface again after resume.

 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 6fcf4fd7ee19..ecc33f797e37 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -7405,11 +7405,13 @@ static int igc_resume(struct device *dev)
 
 	if (netif_running(netdev)) {
 		err = __igc_open(netdev, true);
-		if (!err)
-			netif_device_attach(netdev);
+		if (err)
+			return err;
 	}
 
-	return err;
+	netif_device_attach(netdev);
+
+	return 0;
 }
 
 static int igc_runtime_resume(struct device *dev)
-- 
2.55.0