Subject: Re: [PATCH 01/11] dt-bindings: PCI: generic: Add ats-supported property

From: Rob Herring <[email-masked]>
Date: Wed, 19 Feb 2020 16:24:54 -0600

On Thu, 13 Feb 2020 17:50:39 +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 <[email-masked]>
> ---
>  Documentation/devicetree/bindings/pci/host-generic-pci.yaml | 6 ++++++
>  1 file changed, 6 insertions(+)
> 

Reviewed-by: Rob Herring <[email-masked]>

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