Re: [PATCH] documentation: iommu: add description of ARM System MMU binding

[Rob Herring <robherring2@gmail.com>]

On 04/04/2013 11:50 AM, Will Deacon wrote:
> This patch adds a description of the device tree binding for the ARM
> System MMU architecture.
> 
> Cc: Rob Herring <robherring2@gmail.com>
> Cc: Andreas Herrmann <andreas.herrmann@calxeda.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
> 
> Hello,
> 
> The driver for this is still a WIP. Both Andreas and myself have prototype
> code, but we're planning to merge that together to get something more
> general. Deciding on the binding is a good first step.

Thanks for getting this out.

> All comments welcome,
> 
> Will
> 
>  .../devicetree/bindings/iommu/arm,smmu.txt         | 61 ++++++++++++++++++++++
>  1 file changed, 61 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iommu/arm,smmu.txt
> 
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> new file mode 100644
> index 0000000..938325f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> @@ -0,0 +1,61 @@
> +* 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" or "arm,smmu-v2"
> +                  depending on the version of the architecture
> +                  implemented.

We can keep these, but we should have specific models like arm,smmu-400,
etc. as well.

> +
> +- 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.
> +
> +- mmu-masters   : A list of phandles to device nodes representing bus
> +                  masters for which the SMMU can provide a translation.
> +
> +- stream-ids    : A list of 16-bit values corresponding to the StreamIDs
> +                  for the devices listed in the mmu-masters property.
> +                  This list must be same length as mmu-masters, so
> +                  masters with multiple stream-ids will have multiple
> +                  entries in mmu-masters.

Your example below is actually 32-bit values in the DTB. You can
annotate them to actually be 16-bit if you want. But I would just leave
them as 32-bit.

> +
> +** System MMU optional properties:
> +
> +- smmu-parent   : When multiple SMMUs are chained together, this
> +                  property can be used to provide a phandle to the
> +                  parent SMMU (that is the next SMMU on the path going
> +                  from the mmu-masters towards memory) node for this
> +                  SMMU.

Does the SMMU need to know if it is coherent or not?

Rob

> +
> +Example:
> +
> +        smmu {
> +                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>;
> +                mmu-masters = <&dma0>,
> +                              <&dma0>,
> +                              <&dma1>;
> +                stream-ids  = <0xd01d>,
> +                              <0xd01e>,
> +                              <0xd11c>;
> +        };
>