sunvnet: NAPIfy sunvnet

Move Rx packet procssing to the NAPI poll callback.
Disable VIO interrupt and unconditioanlly go into NAPI
context from vnet_event.

Note that we want to minimize the number of LDC
STOP/START messages sent. Specifically, do not send a STOP
message if vnet_walk_rx does not read all the available descriptors
because of the NAPI budget limitation. Instead, note the end index
as part of port state, and resume from this index when the
next poll callback is triggered.
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Raghuram Kothakota <raghuram.kothakota@oracle.com>
Acked-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sun/sunvnet.h

@@ -56,6 +56,11 @@ struct vnet_port {
 	struct timer_list	clean_timer;
 
 	u64			rmtu;
+
+	struct napi_struct	napi;
+	u32			napi_stop_idx;
+	bool			napi_resume;
+	int			rx_event;
 };
 
 static inline struct vnet_port *to_vnet_port(struct vio_driver_state *vio)
@@ -97,7 +102,6 @@ struct vnet {
 	struct list_head	list;
 	u64			local_mac;
 
-	struct tasklet_struct	vnet_tx_wakeup;
 };
 
 #endif /* _SUNVNET_H */