For context, please see the thread: https://www.spinics.net/lists/arm-kernel/msg539066.html
The existing iommu-map binding did not account for the situation where #iommu-cells == 2, as permitted in the ARM SMMU binding. The 2nd cell of the IOMMU specifier being the SMR mask. The existing binding defines the mapping as: Any RID r in the interval [rid-base, rid-base + length) is associated with the listed IOMMU, with the iommu-specifier (r - rid-base + iommu-base). ...and that does not work if iommu-base is 2 cells, the second being the SMR mask. While this can be worked around by always having length=1, it seems we can get this cleaned up by updating the binding definition for iommu-map. See patch below. Thoughts? Thanks, Stuart ------------------------------------------------------------------------- diff --git a/Documentation/devicetree/bindings/pci/pci-iommu.txt b/Documentation/devicetree/bindings/pci/pci-iommu.txt index 56c8296..e81b461 100644 --- a/Documentation/devicetree/bindings/pci/pci-iommu.txt +++ b/Documentation/devicetree/bindings/pci/pci-iommu.txt @@ -38,8 +38,20 @@ Optional properties The property is an arbitrary number of tuples of (rid-base,iommu,iommu-base,length). - Any RID r in the interval [rid-base, rid-base + length) is associated with - the listed IOMMU, with the iommu-specifier (r - rid-base + iommu-base). + If the associated IOMMU has an #iommu-cells value of 1, any RID r in the + interval [rid-base, rid-base + length) is associated with the listed IOMMU, + with the iommu-specifier (r - rid-base + iommu-base). + + ARM SMMU Note: + The ARM SMMU binding permits an #iommu-cells value of 2 and in this + case defines an IOMMU specifier to be: (stream-id,smr-mask) + + In an iommu-map this means the iommu-base consists of 2 cells: + (rid-base,iommu,[stream-id,smr-mask],length). + + In this case the RID to IOMMU specifier mapping is defined to be: + any RID r in the interval [rid-base, rid-base + length) is associated + with the listed IOMMU, with the iommu-specifier (r - rid-base + stream-id). - iommu-map-mask: A mask to be applied to each Requester ID prior to being mapped to an iommu-specifier per the iommu-map property. _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
