IDT PCI Express 89HPES32NT24xG2, User Manual, Page: 177 / 744

IDT Transparent Switch Operation
PES32NT24xG2 User Manual 10 - 7 January 30, 2013
Notes
– ACS Peer-to-Peer Completion Redirect
– ACS Upstream Forwarding
– ACS Peer-to-Peer Egress Control
– ACS Direct Translated Peer-to-Peer
When a port operates in one of the multi-function upstream port modes listed above, the PCI-to-PCI
bridge function supports the following ACS operations
1
:
– ACS Peer-to-Peer
2
Request Redirect
– ACS Peer-to-Peer Completion Redirect
– ACS Direct Translated Peer-to-Peer
ACS is programmed via the ACS Capability Structure in the PCI-to-PCI bridge function’s configuration
space.
The PCI-to-PCI bridge function only applies ACS checks to TLPs flowing in the upstream direction.
– For a downstream switch port, these are TLPs that are received from the port’s link, regardless of
the final destination of the TLP (e.g., regardless of whether the TLP is going to the upstream port
or a peer downstream switch port).
– For a multi-function upstream port, these are TLPs received by the port’s PCI-to-PCI bridge func-
tion on its secondary side.
When an ACS check causes a TLP to be re-directed, the re-direction is implemented such that TLPs
received by a port that are ACS re-directed follow the ordering rules described in section Packet Ordering
on page 4-6. The following figures show examples of the effect of applying ACS checks to TLPs on the PCI-
to-PCI bridge function.
Figure 10.2 shows an example of ACS source validation at a downstream switch port. In this case, the
offending TLP is dropped and a completion with completer-abort status is generated.
Figure 10.2 ACS Source Validation Example
Figure 10.3 shows an example of ACS peer-to-peer request re-direct at a downstream switch port. In
this case, the offending TLP received by the downstream switch port is re-directed towards the root-
complex.
1.
Note that
the switch
does not support ACS Peer-to-Peer Egress Control among the functions of a multi-func-
tion upstream port.
2.
For a port operating in a multi-function upstream port mode, ‘peer-to-peer’ implies traffic sent from one of the
port functions to another (e.g., from the port’s PCI-to-PCI bridge function to the port’s NT function or vice-versa).
Virtual PCI Bus
P2P
Bridge
Upstream
Port
P2P
Bridge
P2P
Bridge
Downstream Ports
TLP route
Completion with
completer-abort status
ACS Source
Validation
(TLP is
dropped at this
point)