GPnP and GNS are both independent of each other
From 11gR2 onwards, the voting files can be hosted on ASM. And for ASM to come up we need cssd daemon. And for cssd to start the cluster needs to access the voting files.
This information of voting files location is stored in the GPnP (Grid Plug and Play) profile file.
GNS, is for name resolution in the cluster. For clients outside the cluster to find the virtual hosts in the cluster, we provide a Grid Naming Service (GNS). This works with any higher-level DNS to provide resolvable names to external clients. DHCP provides dynamic configuration of the hosts IP address, but does not provide a good way to produce names that are useful to external clients. As a result, it has been uncommon in server complexes. In Oracle Clusterware 11g release 2 (11.2), this problem is solved by providing clusterwares own service for resolving names in the cluster, and connecting this to the DNS that is visible to the clients.
Ref: DNS and DHCP Setup Example for Grid Infrastructure GNS (Doc ID 946452.1)
Vandana - Oracle
Thanks for the clarification.