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

[Robin Murphy]

On 2022-04-28 07:56, Krzysztof Kozlowski wrote:
> 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 at 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

All 4 interrupts are optional, though, since any of them could 
potentially use an MSI instead. Do we really want to list out all 15 
combinations?

Robin.