Re: [PATCH v2 1/5] dt-bindings: virtio: Specify #iommu-cells value for a virtio-iommu

[Rob Herring <robh@kernel.org>]

On Thu, Jun 21, 2018 at 08:06:51PM +0100, Jean-Philippe Brucker wrote:
> A virtio-mmio node may represent a virtio-iommu device. This is discovered
> by the virtio driver at probe time, but the DMA topology isn't
> discoverable and must be described by firmware. For DT the standard IOMMU
> description is used, as specified in bindings/iommu/iommu.txt and
> bindings/pci/pci-iommu.txt. Like many other IOMMUs, virtio-iommu
> distinguishes masters by their endpoint IDs, which requires one IOMMU cell
> in the "iommus" property.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> ---
>  Documentation/devicetree/bindings/virtio/mmio.txt | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/virtio/mmio.txt b/Documentation/devicetree/bindings/virtio/mmio.txt
> index 5069c1b8e193..337da0e3a87f 100644
> --- a/Documentation/devicetree/bindings/virtio/mmio.txt
> +++ b/Documentation/devicetree/bindings/virtio/mmio.txt
> @@ -8,6 +8,14 @@ Required properties:
>  - reg:		control registers base address and size including configuration space
>  - interrupts:	interrupt generated by the device
>  
> +Required properties for virtio-iommu:
> +
> +- #iommu-cells:	When the node describes a virtio-iommu device, it is
> +		linked to DMA masters using the "iommus" property as
> +		described in devicetree/bindings/iommu/iommu.txt. For
> +		virtio-iommu #iommu-cells must be 1, each cell describing
> +		a single endpoint ID.

The iommus property should also be documented for the client side.

Rob