Details:

The system DMA in a PCIe End Point (EP) can issue outbound PCIe requests with the destination select attribute (ASEL) set to a non-zero value. This will enable the PCIe controller to bypass the Address Translation Unit (ATU) and the address issued by the system DMA will be used as the outbound PCIe address.

The function number used in the outbound PCIe Transaction Level Packet (TLP) is incorrectly tied off to 0 when bypassing ATU. As a result, multi-function EP cannot use non-zero ASEL to bypass ATU. All multi-function EP transactions have to be translated by ATU to ensure correct function number in TLP.

If a multi-function EP issues non-zero ASEL transaction, it may result in an Unsupported Request (UR) at the PCIe Root Port (RP).

This issue does not affect single-function EP as function number is always zero.

Workaround(s):

There is no workaround identified for supporting non-zero ASEL outbound transactions in a multi-function EP.