linux_dsm_epyc7002/Documentation/devicetree/bindings/iommu/arm,smmu.txt

* ARM System MMU Architecture Implementation

ARM SoCs may contain an implementation of the ARM System Memory
Management Unit Architecture, which can be used to provide 1 or 2 stages
of address translation to bus masters external to the CPU.

The SMMU may also raise interrupts in response to various fault
conditions.

** System MMU required properties:

- compatible    : Should be one of:

                        "arm,smmu-v1"
                        "arm,smmu-v2"
                        "arm,mmu-400"
                        "arm,mmu-401"
                        "arm,mmu-500"
                        "cavium,smmu-v2"

                  depending on the particular implementation and/or the
                  version of the architecture implemented.

- reg           : Base address and size of the SMMU.

- #global-interrupts : The number of global interrupts exposed by the
                       device.

- interrupts    : Interrupt list, with the first #global-irqs entries
                  corresponding to the global interrupts and any
                  following entries corresponding to context interrupts,
                  specified in order of their indexing by the SMMU.

                  For SMMUv2 implementations, there must be exactly one
                  interrupt per context bank. In the case of a single,
                  combined interrupt, it must be listed multiple times.

- #iommu-cells  : See Documentation/devicetree/bindings/iommu/iommu.txt
                  for details. With a value of 1, each "iommus" entry
                  represents a distinct stream ID emitted by that device
                  into the relevant SMMU.

                  SMMUs with stream matching support and complex masters
                  may use a value of 2, where the second cell represents
                  an SMR mask to combine with the ID in the first cell.
                  Care must be taken to ensure the set of matched IDs
                  does not result in conflicts.

** System MMU optional properties:

- dma-coherent  : Present if page table walks made by the SMMU are
                  cache coherent with the CPU.

                  NOTE: this only applies to the SMMU itself, not
                  masters connected upstream of the SMMU.

- calxeda,smmu-secure-config-access : Enable proper handling of buggy
                  implementations that always use secure access to
                  SMMU configuration registers. In this case non-secure
                  aliases of secure registers have to be used during
                  SMMU configuration.

** Deprecated properties:

- mmu-masters (deprecated in favour of the generic "iommus" binding) :
                  A list of phandles to device nodes representing bus
                  masters for which the SMMU can provide a translation
                  and their corresponding Stream IDs. Each device node
                  linked from this list must have a "#stream-id-cells"
                  property, indicating the number of Stream ID
                  arguments associated with its phandle.

** Examples:

        /* SMMU with stream matching or stream indexing */
        smmu1: iommu {
                compatible = "arm,smmu-v1";
                reg = <0xba5e0000 0x10000>;
                #global-interrupts = <2>;
                interrupts = <0 32 4>,
                             <0 33 4>,
                             <0 34 4>, /* This is the first context interrupt */
                             <0 35 4>,
                             <0 36 4>,
                             <0 37 4>;
                #iommu-cells = <1>;
        };

        /* device with two stream IDs, 0 and 7 */
        master1 {
                iommus = <&smmu1 0>,
                         <&smmu1 7>;
        };


        /* SMMU with stream matching */
        smmu2: iommu {
                ...
                #iommu-cells = <2>;
        };

        /* device with stream IDs 0 and 7 */
        master2 {
                iommus = <&smmu2 0 0>,
                         <&smmu2 7 0>;
        };

        /* device with stream IDs 1, 17, 33 and 49 */
        master3 {
                iommus = <&smmu2 1 0x30>;
        };