[PATCH net 1/1] net: stmmac: fix MAC and phylink mismatch issue after resume with STMMAC_FLAG_USE_PHY_WOL enabled

[Gan Yi Fang]

From: "Gan, Yi Fang" <yi.fang.gan at intel.com>

The issue happened when flag STMMAC_FLAG_USE_PHY_WOL is enabled.
It can be reproduced with steps below:
1. Advertise only one speed on the host
2. Enable the WoL on the host
3. Suspend the host
4. Wake up the host

When the WoL is disabled, both the PHY and MAC will suspend and wake up
with everything configured well. When WoL is enabled, the PHY needs to be
stay awake to receive the signal from remote client but MAC will enter
suspend mode.

When the MAC resumes from suspend, phylink_resume() will call
phylink_start() to start the phylink instance which will trigger the
phylink machine to invoke the mac_link_up callback function. The
stmmac_mac_link_up() will configure the MAC_CTRL_REG based on the current
link state. Then the stmmac_hw_setup() will be called to configure the MAC.

This sequence might cause mismatch of the link state between MAC and
phylink. This patch moves the phylink_resume() after stmamc_hw_setup() to
ensure the MAC is initialized before phylink is being configured.

As phylink_resume() is called all the time, refactor the code and
remove the redundant check.

Fixes: 90702dcd19c0 ("net: stmmac: fix MAC not working when system resume back with WoL active")
Cc: <stable at vger.kernel.org> # 5.15+
Signed-off-by: Gan, Yi Fang <yi.fang.gan at intel.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 3e50fd53a617..9b009fa5478f 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -7844,16 +7844,6 @@ int stmmac_resume(struct device *dev)
 			return ret;
 	}
 
-	rtnl_lock();
-	if (device_may_wakeup(priv->device) && priv->plat->pmt) {
-		phylink_resume(priv->phylink);
-	} else {
-		phylink_resume(priv->phylink);
-		if (device_may_wakeup(priv->device))
-			phylink_speed_up(priv->phylink);
-	}
-	rtnl_unlock();
-
 	rtnl_lock();
 	mutex_lock(&priv->lock);
 
@@ -7868,6 +7858,11 @@ int stmmac_resume(struct device *dev)
 
 	stmmac_restore_hw_vlan_rx_fltr(priv, ndev, priv->hw);
 
+	phylink_resume(priv->phylink);
+
+	if (device_may_wakeup(priv->device) && !(priv->plat->pmt))
+		phylink_speed_up(priv->phylink);
+
 	stmmac_enable_all_queues(priv);
 	stmmac_enable_all_dma_irq(priv);
 
-- 
2.34.1