liquidio: Fix an issue with multiple switchdev enable disables

Return success if the same dispatch function is being registered for
a given opcode and subcode, there by allow multiple switchdev enable
and disables.

Signed-off-by: Vijaya Mohan Guvva <vijaya.guvva@cavium.com>
Signed-off-by: Satanand Burla <satananda.burla@cavium.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cavium/liquidio/octeon_device.c

@@ -1180,6 +1180,10 @@ octeon_register_dispatch_fn(struct octeon_device *oct,
 		spin_unlock_bh(&oct->dispatch.lock);
 
 	} else {
+		if (pfn == fn &&
+		    octeon_get_dispatch_arg(oct, opcode, subcode) == fn_arg)
+			return 0;
+
 		dev_err(&oct->pci_dev->dev,
 			"Found previously registered dispatch fn for opcode/subcode: %x/%x\n",
 			opcode, subcode);

drivers/net/ethernet/cavium/liquidio/octeon_droq.c

@@ -52,8 +52,8 @@ struct __dispatch {
  *  @return  Failure: NULL
  *
  */
-static inline void *octeon_get_dispatch_arg(struct octeon_device *octeon_dev,
-					    u16 opcode, u16 subcode)
+void *octeon_get_dispatch_arg(struct octeon_device *octeon_dev,
+			      u16 opcode, u16 subcode)
 {
 	int idx;
 	struct list_head *dispatch;

drivers/net/ethernet/cavium/liquidio/octeon_droq.h

@@ -400,6 +400,9 @@ int octeon_register_dispatch_fn(struct octeon_device *oct,
 				u16 subcode,
 				octeon_dispatch_fn_t fn, void *fn_arg);
 
+void *octeon_get_dispatch_arg(struct octeon_device *oct,
+			      u16 opcode, u16 subcode);
+
 void octeon_droq_print_stats(void);
 
 u32 octeon_droq_check_hw_for_pkts(struct octeon_droq *droq);