Transactions on the AXI bus contain a Stream ID. SMMUs filter

Transactions on the AXI bus contain a Stream ID.  SMMUs filter
based on Stream IDs.  On the Armada 8040 these Stream IDs can
be configured in different registers.  The PCIe controller has
a register which maps root port, bus, dev and func number to
the Stream ID.  This should be set up by TF-A firmware, but on
the 8040 the current images don't do this.  For chips with more
than one PCIe controller this register must be setup correctly
depending on the implementation, but on the 8040 there only is
one controller, so we can configure a fixed value to match what
is defined in the device tree.  This allows the SMMU to properly
track the PCIe controller's transactions.

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