Re: [PATCH 01/11] dt-bindings: iommu: arm,smmu-v3: make PRI IRQ optional

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 27/04/2022 13:25, Andre Przywara wrote:
> The Page Request Interface (PRI) is an optional PCIe feature. As such, a
> SMMU would not need to handle it if the PCIe host bridge or the SMMU
> itself do not implement it. Also an SMMU could be connected to a platform
> device, without any PRI functionality whatsoever.
> In all cases there would be no SMMU PRI queue interrupt to be wired up
> to an interrupt controller.
> 
> Relax the binding to allow specifying three interrupts, omitting the PRI
> IRQ. At the moment, with the "eventq,gerror,priq,cmdq-sync" order, we
> would need to sacrifice the command queue sync interrupt as well, which
> might not be desired.
> The Linux driver does not care about any order at all, just picks IRQs
> based on their names, and treats all (wired) IRQs as optional.

The last sentence is not a good explanation for the bindings. They are
not about Linux and are used in other projects as well.

> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  .../bindings/iommu/arm,smmu-v3.yaml           | 21 ++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
> index e87bfbcc69135..6b3111f1f06ce 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
> @@ -37,12 +37,23 @@ properties:
>            hardware supports just a single, combined interrupt line.
>            If provided, then the combined interrupt will be used in preference to
>            any others.
> -      - minItems: 2
> +      - minItems: 1
>          items:
> -          - const: eventq     # Event Queue not empty
> -          - const: gerror     # Global Error activated
> -          - const: priq       # PRI Queue not empty
> -          - const: cmdq-sync  # CMD_SYNC complete
> +          - enum:
> +              - eventq     # Event Queue not empty
> +              - gerror     # Global Error activated
> +              - cmdq-sync  # CMD_SYNC complete
> +              - priq       # PRI Queue not empty
> +          - enum:
> +              - gerror
> +              - cmdq-sync
> +              - priq
> +          - enum:
> +              - cmdq-sync
> +              - priq
> +          - enum:
> +              - cmdq-sync
> +              - priq

The order should be strict, so if you want the first interrupt optional,
then:
oneOf:
 - items:
    ... 4 items list
 - items
    ... 3 items list

Best regards,
Krzysztof