mlxsw: spectrum: Use different seeds for ECMP and LAG hash

The same hash function and seed are used for both ECMP and LAG hash.
Therefore, when a LAG device is used as a nexthop device as part of an
ECMP group, hash polarization can occur and all the traffic will be
hashed to a single LAG slave.

Fix this by using a different seed for the LAG hash.

Fixes: fa73989f ("mlxsw: spectrum: Use a stable ECMP/LAG seed")
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Reported-by: NAlex Veber <alexve@mellanox.com>
Tested-by: NAlex Veber <alexve@mellanox.com>
Acked-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -4280,13 +4280,16 @@ static void mlxsw_sp_traps_fini(struct mlxsw_sp *mlxsw_sp)
 	}
 }
 
+#define MLXSW_SP_LAG_SEED_INIT 0xcafecafe
+
 static int mlxsw_sp_lag_init(struct mlxsw_sp *mlxsw_sp)
 {
 	char slcr_pl[MLXSW_REG_SLCR_LEN];
 	u32 seed;
 	int err;
 
-	seed = jhash(mlxsw_sp->base_mac, sizeof(mlxsw_sp->base_mac), 0);
+	seed = jhash(mlxsw_sp->base_mac, sizeof(mlxsw_sp->base_mac),
+		     MLXSW_SP_LAG_SEED_INIT);
 	mlxsw_reg_slcr_pack(slcr_pl, MLXSW_REG_SLCR_LAG_HASH_SMAC |
 				     MLXSW_REG_SLCR_LAG_HASH_DMAC |
 				     MLXSW_REG_SLCR_LAG_HASH_ETHERTYPE |