| Message ID | 20200213165049.508908-2-jean-philippe@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | PCI/ATS: Device-tree support and other improvements | expand |
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 <jean-philippe@linaro.org> > --- > Documentation/devicetree/bindings/pci/host-generic-pci.yaml | 6 ++++++ > 1 file changed, 6 insertions(+) > Reviewed-by: Rob Herring <robh@kernel.org>
diff --git a/Documentation/devicetree/bindings/pci/host-generic-pci.yaml b/Documentation/devicetree/bindings/pci/host-generic-pci.yaml index 47353d0cd394..7d40edd7f1ef 100644 --- a/Documentation/devicetree/bindings/pci/host-generic-pci.yaml +++ b/Documentation/devicetree/bindings/pci/host-generic-pci.yaml @@ -107,6 +107,12 @@ properties: dma-coherent: 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
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> --- Documentation/devicetree/bindings/pci/host-generic-pci.yaml | 6 ++++++ 1 file changed, 6 insertions(+)