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Date:   Tue, 16 Aug 2022 10:25:26 +0300
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Subject: Re: [PATCH 2/4] dt-bindings: PCI: microchip,pcie-host: fix missing
 clocks properties
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To:     Conor.Dooley@microchip.com, mail@conchuod.ie,
        Daire.McNamara@microchip.com, bhelgaas@google.com,
        robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        paul.walmsley@sifive.com, greentime.hu@sifive.com,
        palmer@dabbelt.com, aou@eecs.berkeley.edu, lpieralisi@kernel.org
Cc:     linux-pci@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org
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From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
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On 14/08/2022 16:47, Conor.Dooley@microchip.com wrote:
> On 12/08/2022 08:35, Krzysztof Kozlowski wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> On 11/08/2022 23:33, Conor Dooley wrote:
>>> From: Conor Dooley <conor.dooley@microchip.com>
>>>
>>> Upgrading dt-schema to v2022.08 reveals unevaluatedProperties issues
>>> that were not previously visible, such as the missing clocks and
>>> clock-names properties for PolarFire SoC's PCI controller:
>>> arch/riscv/boot/dts/microchip/mpfs-icicle-kit.dtb: pcie@2000000000: Unevaluated properties are not allowed ('clock-names', 'clocks', 'legacy-interrupt-controller', 'microchip,axi-m-atr0' were unexpected)
>>>         From schema: Documentation/devicetree/bindings/pci/microchip,pcie-host.yaml
>>>
>>> The clocks are required to enable interfaces between the FPGA fabric
>>> and the core complex, so add them to the binding.
>>>
>>> Fixes: 6ee6c89aac35 ("dt-bindings: PCI: microchip: Add Microchip PolarFire host binding")
>>> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>>> ---
>>>  .../bindings/pci/microchip,pcie-host.yaml     | 25 +++++++++++++++++++
>>>  1 file changed, 25 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/pci/microchip,pcie-host.yaml b/Documentation/devicetree/bindings/pci/microchip,pcie-host.yaml
>>> index edb4f81253c8..2a2166f09e2c 100644
>>> --- a/Documentation/devicetree/bindings/pci/microchip,pcie-host.yaml
>>> +++ b/Documentation/devicetree/bindings/pci/microchip,pcie-host.yaml
>>> @@ -25,6 +25,31 @@ properties:
>>>        - const: cfg
>>>        - const: apb
>>>
>>> +  clocks:
>>> +    description:
>>> +      Fabric Interface Controllers, FICs, are the interface between the FPGA
>>> +      fabric and the core complex on PolarFire SoC. The FICs require two clocks,
>>> +      one from each side of the interface. The "FIC clocks" described by this
>>> +      property are on the core complex side & communication through a FIC is not
>>> +      possible unless it's corresponding clock is enabled. A clock must be
>>> +      enabled for each of the interfaces the root port is connected through.
>>> +    minItems: 1
>>> +    items:
>>> +      - description: FIC0's clock
>>> +      - description: FIC1's clock
>>> +      - description: FIC2's clock
>>> +      - description: FIC3's clock
>>> +
>>> +  clock-names:
>>> +    items:
>>> +      enum:
>>> +        - fic0
>>> +        - fic1
>>> +        - fic2
>>> +        - fic3
>>> +    minItems: 1
>>> +    maxItems: 4
>>
>> No need for maxItems.
> 
> I brought this up on IRC, but transferring it here since it's been
> an (understandable!!) few days & just didn't want things to get lost
> if my net died. Cutting out the back & forth, in summary:
> "
> I'm trying to remove the maxItems from the clock-names array you
> didn't like - but I can't figure out what to do instead that doesn't
> trigger errors. All 4 clocks are optional, the only requirement is
> that any one of them is present. Either I seem to get complaints that
> my property is not an array (simply removing the maxItems) or complaints
> that because I have clock0,1,3 and not 2 that clock3 is unexpected.

Eh, I misread the code and thought that you list the items, but you just
enumerate the schema for each item. My advice was wrong, you need maxItems.

> The root port is physically on the opposite side of the FPGA to the cpus
> & the AXI connection is through the FPGA fabric. There are 4 AXI
> interconnects to the fabric  which the PCI controller could in theory be
> connected to all 4, but it only needs to be connected to one.. I had
> done done minItems and maxItems a la:
> devicetree/bindings/watchdog/st,stm32-iwdg.yaml
> b/c that seems to have two clocks that it doesnt care about the order of
> "
> 
> Rob then suggested:
> "
> I would remove the 'items' list in 'clocks' and make the description
> clear that any of clocks is possible. It's not ideal, but it's a case of
> that's what is already there.
> "
> 
> I'd then have something along the lines of:
>   clocks:
>     description:
>       Fabric Interface Controllers, FICs, are the interface between the FPGA
>       fabric and the core complex on PolarFire SoC. The FICs require two clocks,
>       one from each side of the interface. The "FIC clocks" described by this
>       property are on the core complex side & communication through a FIC is not
>       possible unless it's corresponding clock is enabled. A clock must be
>       enabled for each of the interfaces the root port is connected through.
>       This could in theory be all 4 interfaces, one interface or any combination
>       in between.
>     minItems: 1
>     maxItems: 4
> 
>   clock-names:
>     items:
>       enum:
>         - fic0
>         - fic1
>         - fic2
>         - fic3
>     minItems: 1
>     maxItems: 4
> 
> Does that seem reasonable to you?


Yes.

Best regards,
Krzysztof