On Tue, Feb 21, 2023 at 09:46:24AM -0600, Bjorn Helgaas wrote:

It's weird to me that the SMMU is between PCI and memory, but the
driver seems to insert itself in the middle after PCI enumeration.
And maybe even after some PCI device driver binding?

No this shouldn't happen, because device drivers expect DMA to be
operational in their probe() function, so at that point the IOMMU must be
configured. The core and IOMMU subsystems enforce probe dependency between
the SMMU and the PCI device, using links described by ACPI or device tree.

Thanks,
Jean

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