The PCIe controller in Tegra194 SoC is not ECAM-compliant.  With the
current hardware design, ECAM can be enabled only for one controller (the
C5 controller) with bus numbers starting from 160 instead of 0. A different
approach is taken to avoid this abnormal way of enabling ECAM for just one
controller but to enable configuration space access for all the other
controllers. In this approach, ops are added through MCFG quirk mechanism
which access the configuration spaces by dynamically programming iATU
(internal AddressTranslation Unit) to generate respective configuration
accesses just like the way it is done in DesignWare core sub-system.

This issue is specific to Tegra194 and it would be fixed in the future
generations of Tegra SoCs.

Link: https://lore.kernel.org/r/20210416134537.19474-1-vidyas@nvidia.comSigned-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>