Re: [PATCH v8 1/5] dt-bindings: reserved-memory: Document iommu-addresses

[Rob Herring <robh@kernel.org>]

On Mon, Sep 05, 2022 at 07:08:29PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> This adds the "iommu-addresses" property to reserved-memory nodes, which
> allow describing the interaction of memory regions with IOMMUs. Two use-
> cases are supported:
> 
>   1. Static mappings can be described by pairing the "iommu-addresses"
>      property with a "reg" property. This is mostly useful for adopting
>      firmware-allocated buffers via identity mappings. One common use-
>      case where this is required is if early firmware or bootloaders
>      have set up a bootsplash framebuffer that a display controller is
>      actively scanning out from during the operating system boot
>      process.
> 
>   2. If an "iommu-addresses" property exists without a "reg" property,
>      the reserved-memory node describes an IOVA reservation. Such memory
>      regions are excluded from the IOVA space available to operating
>      system drivers and can be used for regions that must not be used to
>      map arbitrary buffers.
> 
> Each mapping or reservation is tied to a specific device via a phandle
> to the device's device tree node. This allows a reserved-memory region
> to be reused across multiple devices.
> 
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---
> Changes in v8:
> - include validation warning fixes that had crept into an unrelated patch
> 
> Changes in v7:
> - keep reserved-memory.txt to avoid broken references
> 
> Changes in v6:
> - add device phandle to iommu-addresses property in examples
> - remove now unused dt-bindings/reserved-memory.h header
> 
>  .../reserved-memory/reserved-memory.yaml      | 70 +++++++++++++++++++
>  1 file changed, 70 insertions(+)

Thanks for being persistent with this. It looks good to me.

Reviewed-by: Rob Herring <robh@kernel.org>

I really don't like new common bindings with only 1 user, so I hope the 
Asahi folks chime in here. Or really anyone else look at it.

Rob