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

Message ID 20240429113938.192706-3-jean-philippe@linaro.org
State New
Headers show
Series Enable PCIe ATS for devicetree boot | expand

Commit Message

Jean-Philippe Brucker April 29, 2024, 11:39 a.m. UTC 
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>
---
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(+)

Comments

Liviu Dudau April 30, 2024, 10:22 a.m. UTC | #1 
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
>
diff mbox series

Patch

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