Re: [RFC 1/5] dt-bindings: iommu: Add reserved-dma-region for IOMMU device

[Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>]

On 06/03/18 04:59, Jitendra Bhivare wrote:
> Certain regions in IO virtual address space may need to be reserved to be
> not used for devices configured behind IOMMU.
> 
> Add documentation of the property to allow such regions to be specified in
> DT to be reserved using IOMMU_RESV_RESERVED type.

That sounds like software policy; DT is for describing hardware.

> Reviewed-by: Ray Jui <ray.jui-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Reviewed-by: Vikram Prakash <vikram.prakash-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Reviewed-by: Scott Branden <scott.branden-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Signed-off-by: Jitendra Bhivare <jitendra.bhivare-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> ---
>   Documentation/devicetree/bindings/iommu/iommu.txt | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iommu/iommu.txt b/Documentation/devicetree/bindings/iommu/iommu.txt
> index 5a8b462..5a58ef2 100644
> --- a/Documentation/devicetree/bindings/iommu/iommu.txt
> +++ b/Documentation/devicetree/bindings/iommu/iommu.txt
> @@ -98,6 +98,20 @@ requirements of that use-case haven't been fully determined yet. Implementing
>   this is therefore not recommended without further discussion and extension of
>   this binding.
>   
> +Optional properties:
> +--------------------
> +- reserved-dma-region: This specifies DMA region to be reserved with specific
> +  prot in IOVA space. It is in tuples of (busno,prot,bus_addr,size).

What do busno and prot actually mean, and what are valid values for them?

Robin.

> +- #region-address-cells: specifies number of cells needed to encode bus_addr
> +
> +- #region-size-cells: specifies number of cells needed to encode size
> +
> +Notes:
> +======
> +This can be applied to IOMMU master node or to children (such as PCI host
> +bridges) on the bus behind IOMMU.
> +
>   
>   Examples:
>   =========
> @@ -173,6 +187,9 @@ Multiple-master IOMMU with configurable DMA window:
>   			 * master (i.e. the I/O virtual address space).
>   			 */
>   			#iommu-cells = <4>;
> +			#region-address-cells = <2>;
> +			#region-size-cells = <2>;
> +			reserved-dma-region = <0x0 0x0 0x04 0x0 0x04 0x0>;
>   		};
>   
>   		master {
>