Alexandre Bounine wrote:

A switch ingress port number has to be saved for software assisted error
recovery from the error-stopped state. Saving this information also allows
to remove several register reads from the RIO enumeration process.

Why not keep using the swpinfo field, as you can extract it from there? 
And your code actually does this.

Also processor devices can have multiple ports (not only switches), it 
would be good to be ready for that use case.

Micha