pcie transactions

                     Egress(outbound)                                                 Ingress(inbound)

              as Root                      as endpoint                             as Root                      as endpoint

Posted mem wr req           posted mem wr req            posted mem wr req       posted mem wr req

non-posted mem rd req   non-posted mem rd req    non-posted mem rd req  non-posted mem rd req

mem rd completion          mem rd completion           mem rd completion          mem rd completion

cfg req (type 0/1)             cfg completion(type 0)      cfg completion(type 0/1)   cfg req(type 0)

io req                                 io completion                   io completion                   io req

pwr mgr req to endpoint   pwr mgr msg to root   pwr mgr msg from endpoint  pwr mgm req from root

                                          msi msg/intx msg

                                           err msg/PME_TO_ACK