[SUNGEM]: Fix suspend regression due to NAPI changes.

Commit bea3348 (the NAPI changes) made sungem unconditionally enable
NAPI when resuming and unconditionally disable when suspending, this,
however, makes napi_disable() hang when suspending when the interface
was taken down before suspend because taking the interface down also
disables NAPI. This patch makes touching the napi struct in
suspend/resume code paths depend on having the interface up, thereby
fixing the hang on suspend.

The patch also moves the napi_disable() in gem_close() under the lock so
that the NAPI state is always modified atomically together with the
"opened" variable.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sungem.c

@@ -2333,10 +2333,10 @@ static int gem_close(struct net_device *dev)
 {
 	struct gem *gp = dev->priv;
 
-	napi_disable(&gp->napi);
-
 	mutex_lock(&gp->pm_mutex);
 
+	napi_disable(&gp->napi);
+
 	gp->opened = 0;
 	if (!gp->asleep)
 		gem_do_stop(dev, 0);
@@ -2355,8 +2355,6 @@ static int gem_suspend(struct pci_dev *pdev, pm_message_t state)
 
 	mutex_lock(&gp->pm_mutex);
 
-	napi_disable(&gp->napi);
-
 	printk(KERN_INFO "%s: suspending, WakeOnLan %s\n",
 	       dev->name,
 	       (gp->wake_on_lan && gp->opened) ? "enabled" : "disabled");
@@ -2370,6 +2368,8 @@ static int gem_suspend(struct pci_dev *pdev, pm_message_t state)
 
 	/* If the driver is opened, we stop the MAC */
 	if (gp->opened) {
+		napi_disable(&gp->napi);
+
 		/* Stop traffic, mark us closed */
 		netif_device_detach(dev);
 
@@ -2460,6 +2460,7 @@ static int gem_resume(struct pci_dev *pdev)
 		/* Re-attach net device */
 		netif_device_attach(dev);
 
+		napi_enable(&gp->napi);
 	}
 
 	spin_lock_irqsave(&gp->lock, flags);
@@ -2479,8 +2480,6 @@ static int gem_resume(struct pci_dev *pdev)
 	spin_unlock(&gp->tx_lock);
 	spin_unlock_irqrestore(&gp->lock, flags);
 
-	napi_enable(&gp->napi);
-
 	mutex_unlock(&gp->pm_mutex);
 
 	return 0;