net: smsc911x: Stop and start PHY during suspend and resume

Commit 744d23c7 ("net: phy: Warn about incorrect
mdio_bus_phy_resume() state") unveiled that the smsc911x driver was not
properly stopping and restarting the PHY during suspend/resume. Correct
that by indicating that the MAC is in charge of PHY PM operations and
ensure that all MDIO bus activity is quiescent during suspend.
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Fixes: fba863b8 ("net: phy: make PHY PM ops a no-op if MAC driver manages PHY PM")
Fixes: 2aa70f86 ("net: smsc911x: Quieten netif during suspend")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220825023951.3220-1-f.fainelli@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/smsc/smsc911x.c

@@ -1037,6 +1037,8 @@ static int smsc911x_mii_probe(struct net_device *dev)
 		return ret;
 	}
 
+	/* Indicate that the MAC is responsible for managing PHY PM */
+	phydev->mac_managed_pm = true;
 	phy_attached_info(phydev);
 
 	phy_set_max_speed(phydev, SPEED_100);
@@ -2587,6 +2589,8 @@ static int smsc911x_suspend(struct device *dev)
 	if (netif_running(ndev)) {
 		netif_stop_queue(ndev);
 		netif_device_detach(ndev);
+		if (!device_may_wakeup(dev))
+			phy_stop(ndev->phydev);
 	}
 
 	/* enable wake on LAN, energy detection and the external PME
@@ -2628,6 +2632,8 @@ static int smsc911x_resume(struct device *dev)
 	if (netif_running(ndev)) {
 		netif_device_attach(ndev);
 		netif_start_queue(ndev);
+		if (!device_may_wakeup(dev))
+			phy_start(ndev->phydev);
 	}
 
 	return 0;