Re: [PATCH 1/3] dt-bindings: PCI: generic: Add ats-supported property

[Liviu Dudau <liviu.dudau@arm.com>]

On Mon, Apr 29, 2024 at 12:39:37PM +0100, Jean-Philippe Brucker wrote:
> Add a way for firmware to tell the OS that ATS is supported by the PCI
> root complex. An endpoint with ATS enabled may send Translation Requests
> and Translated Memory Requests, which look just like Normal Memory
> Requests with a non-zero AT field. So a root controller that ignores the
> AT field may simply forward the request to the IOMMU as a Normal Memory
> Request, which could end badly. In any case, the endpoint will be
> unusable.
> 
> The ats-supported property allows the OS to only enable ATS in endpoints
> if the root controller can handle ATS requests. Only add the property to
> pcie-host-ecam-generic for the moment. For non-generic root controllers,
> availability of ATS can be inferred from the compatible string.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Reviewed-by: Rob Herring <robh@kernel.org>

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

> ---
> From a while ago: https://lore.kernel.org/all/20200219222454.GA16221@bogus/
> ---
>  Documentation/devicetree/bindings/pci/host-generic-pci.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/host-generic-pci.yaml b/Documentation/devicetree/bindings/pci/host-generic-pci.yaml
> index d25423aa71674..94d4a4914a483 100644
> --- a/Documentation/devicetree/bindings/pci/host-generic-pci.yaml
> +++ b/Documentation/devicetree/bindings/pci/host-generic-pci.yaml
> @@ -110,6 +110,12 @@ properties:
>    iommu-map-mask: true
>    msi-parent: true
>  
> +  ats-supported:
> +    description:
> +      Indicates that a PCIe host controller supports ATS, and can handle Memory
> +      Requests with Address Type (AT).
> +    type: boolean
> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.44.0
> 

-- 
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