net: stmmac: only call pmt() during suspend/resume if HW enables PMT

This is to prepare WOL support with phy. Compared with WOL
implementation which relies on the MAC's PMT features, in phy
supported WOL case, device_may_wakeup() may also be true, but we
should not call mac's pmt() function if HW doesn't enable PMT.

And during resume, we should call phylink_start() if PMT is disabled.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -5085,7 +5085,7 @@ int stmmac_suspend(struct device *dev)
 		priv->plat->serdes_powerdown(ndev, priv->plat->bsp_priv);
 
 	/* Enable Power down mode by programming the PMT regs */
-	if (device_may_wakeup(priv->device)) {
+	if (device_may_wakeup(priv->device) && priv->plat->pmt) {
 		stmmac_pmt(priv, priv->hw, priv->wolopts);
 		priv->irq_wake = 1;
 	} else {
@@ -5157,7 +5157,7 @@ int stmmac_resume(struct device *dev)
 	 * this bit because it can generate problems while resuming
 	 * from another devices (e.g. serial console).
 	 */
-	if (device_may_wakeup(priv->device)) {
+	if (device_may_wakeup(priv->device) && priv->plat->pmt) {
 		mutex_lock(&priv->lock);
 		stmmac_pmt(priv, priv->hw, 0);
 		mutex_unlock(&priv->lock);
@@ -5200,7 +5200,7 @@ int stmmac_resume(struct device *dev)
 
 	mutex_unlock(&priv->lock);
 
-	if (!device_may_wakeup(priv->device)) {
+	if (!device_may_wakeup(priv->device) || !priv->plat->pmt) {
 		rtnl_lock();
 		phylink_start(priv->phylink);
 		rtnl_unlock();