IDT PCI Express 89HPES32NT24xG2, User Manual, Page: 285 / 744

IDT Non-Transparent Switch Operation
PES32NT24xG2 User Manual 14 - 37 January 30, 2013
Notes
ACS Errors
ACS checks may cause the offending TLP to be dropped (i.e., ACS violation) or re-directed towards the
root-complex by the detecting function. In cases where the TLP is dropped, no other functions in the TLP’s
logical path detect the ACS error. In cases where the TLP is re-directed towards the root-complex, other
functions in the TLP’s logical path may perform ACS checks on the TLP.
ACS re-direction may occur at three logical points in a TLPs path:
– Downstream switch port: A TLP received on a downstream switch port that is destined towards
another downstream switch port in the same partition is re-directed towards the root-complex
(Figure 10.3).
– Upstream port’s PCI-to-PCI Bridge function: A TLP received on the upstream PCI-to-PCI bridge
function’s secondary side that is destined towards the NT function in the same port is re-directed
towards the root-complex (Figure 10.5).
– Upstream port’s NT function: A TLP transmitted by the upstream NT function’s that is destined
towards the PCI-to-PCI bridge function in the same port is re-directed towards the root-complex
(Figure 14.12).
Refer to section Access Control Services on page 10-6 for details on ACS checks performed by the PCI-
to-PCI bridge function, and section Access Control Services (ACS) on page 14-23 for details on ACS
checks performed by the NT function.
Combined Transaction Layer Errors
As a TLP is logically routed across the PES32NT24xG2 functions, it is possible for functions to detect
different types of transaction layer errors for the TLP. For example, on reception of a TLP, a PCI-to-PCI
bridge function may log a poisoned TLP error and forward the TLP to the next function in its logical route.
This next function may detect an unsupported request (UR) error on the TLP and handle it accordingly
1
.
In general, when a first function receives a TLP, detects an error, and forwards the TLP to the next func-
tion on the route, the next function in the TLP’s path may not detect an error, may detect the same error, or
may detect a higher priority error.
Figure 14.17 shows an example of a poisoned non-posted TLP received on a downstream switch port of
a first partition. As the TLP propagates within the first partition, across the NTB, and towards a second parti-
tion, the functions in the logical path of the TLP log the poisoned TLP error reception appropriately. As the
TLP reaches a downstream switch port in the second partition, the port’s PCI-to-PCI bridge function detects
NT Endpoint (Partition 2) Refer to row corresponding to ‘Poisoned TLP
received’ in Table 14.4. In the table, this NT
function is considered the “NT endpoint in the
destination partition”.
Upstream PCI-to-PCI Bridge (Partition 2) Refer to row corresponding to ‘Poisoned TLP
received’ error in Table 10.9
Note that the bridge only logs parity error recep-
tion in the PCISTS register as it did not receive
the TLP directly from the link.
Downstream PCI-to-PCI Bridge
(Partition 2) Refer to row corresponding to ‘Poisoned TLP
received’ error in Table 10.9
Note that the bridge only logs parity error recep-
tion in the PCISTS register as it did not receive
the TLP directly from the link.
1.
Note that UR errors have higher precedence than poisoned TLP errors per the error pollution rules described in
section Transaction Layer Error Pollution on page 14-31.
Function Error Logging
Table 14.9 Error Logging at Each Function for Poisoned TLP Example (Part 2 of 2)