epic100: allow nesting of ethtool_ops begin() and complete()

Unlike most networking drivers using begin() and complete() ethtool_ops
callbacks to resume a device which is down and suspend it again when done,
epic100 does not use standard refcounted infrastructure but sets device
sleep state directly.

With the introduction of netlink ethtool interface, we may have nested
begin-complete blocks so that inner complete() would put the device back to
sleep for the rest of the outer block.

To avoid rewriting an old and not very actively developed driver, just add
a nesting counter and only perform resume and suspend on the outermost
level.
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/smsc/epic100.c

@@ -280,6 +280,7 @@ struct epic_private {
 	signed char phys[4];				/* MII device addresses. */
 	u16 advertising;					/* NWay media advertisement */
 	int mii_phy_cnt;
+	u32 ethtool_ops_nesting;
 	struct mii_if_info mii;
 	unsigned int tx_full:1;				/* The Tx queue is full. */
 	unsigned int default_port:4;		/* Last dev->if_port value. */
@@ -1435,8 +1436,10 @@ static int ethtool_begin(struct net_device *dev)
 	struct epic_private *ep = netdev_priv(dev);
 	void __iomem *ioaddr = ep->ioaddr;
 
+	if (ep->ethtool_ops_nesting == U32_MAX)
+		return -EBUSY;
 	/* power-up, if interface is down */
-	if (!netif_running(dev)) {
+	if (!ep->ethtool_ops_nesting++ && !netif_running(dev)) {
 		ew32(GENCTL, 0x0200);
 		ew32(NVCTL, (er32(NVCTL) & ~0x003c) | 0x4800);
 	}
@@ -1449,7 +1452,7 @@ static void ethtool_complete(struct net_device *dev)
 	void __iomem *ioaddr = ep->ioaddr;
 
 	/* power-down, if interface is down */
-	if (!netif_running(dev)) {
+	if (!--ep->ethtool_ops_nesting && !netif_running(dev)) {
 		ew32(GENCTL, 0x0008);
 		ew32(NVCTL, (er32(NVCTL) & ~0x483c) | 0x0000);
 	}