linux-kernel - Re: [PATCH 1/3] dt-bindings: PCI: ti,j721e-pci-*: Fix check for num-lanes

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Message-ID: <bd3e809f-5d97-428f-9387-a2475c4f0d7d@linaro.org>
Date: Wed, 17 Jan 2024 11:53:53 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Siddharth Vadapalli <s-vadapalli@...com>
Cc: bhelgaas@...gle.com, lpieralisi@...nel.org, kw@...ux.com,
 robh@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 vigneshr@...com, afd@...com, srk@...com
Subject: Re: [PATCH 1/3] dt-bindings: PCI: ti,j721e-pci-*: Fix check for
 num-lanes

On 17/01/2024 11:47, Siddharth Vadapalli wrote:
> Hello Krzysztof,
> 
> On 17/01/24 16:04, Krzysztof Kozlowski wrote:
>> On 17/01/2024 11:25, Siddharth Vadapalli wrote:
>>> The existing implementation for validating the "num-lanes" property
>>> based on the compatible(s) doesn't enforce it. Fix it by updating the
>>> checks to handle both single-compatible and multi-compatible cases.
>>>
>>> Fixes: b3ba0f6e82cb ("dt-bindings: PCI: ti,j721e-pci-*: Add checks for num-lanes")
>>> Fixes: adc14d44d7cb ("dt-bindings: PCI: ti,j721e-pci-*: Add j784s4-pci-* compatible strings")
>>> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
>>> ---
>>>  .../bindings/pci/ti,j721e-pci-ep.yaml         | 26 ++++++++++++++-----
>>>  .../bindings/pci/ti,j721e-pci-host.yaml       | 26 ++++++++++++++-----
>>>  2 files changed, 38 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/pci/ti,j721e-pci-ep.yaml b/Documentation/devicetree/bindings/pci/ti,j721e-pci-ep.yaml
>>> index 97f2579ea908..278e0892f8ac 100644
>>> --- a/Documentation/devicetree/bindings/pci/ti,j721e-pci-ep.yaml
>>> +++ b/Documentation/devicetree/bindings/pci/ti,j721e-pci-ep.yaml
>>> @@ -68,8 +68,9 @@ allOf:
>>>    - if:
>>>        properties:
>>>          compatible:
>>
>> Missing contains:, instead of your change.
> 
> I did try the "contains" approach before determining that the implementation in
> this patch is more suitable. Please consider the following:
> 
> For AM64 SoC the primary compatible is "ti,am64-pcie-ep" and fallback compatible
> is "ti,j721e-pcie-ep". For J7200 SoC the primary compatible is
> "ti,j7200-pcie-ep" while the fallback compatible is again "ti,j721e-pcie-ep".
> 
> Therefore, the device-tree nodes for AM64 and J7200 look like:
> 
> AM64:
>     compatible = "ti,am64-pcie-ep", "ti,j721e-pcie-ep";
>     ...
>     num-lanes = 1;
> 
> J7200:
>     compatible = "ti,j7200-pcie-ep", "ti,j721e-pcie-ep";
>     ...
>     num-lanes = 4;
> 
> This implies that when the check for "num-lanes" is performed on the device-tree
> node for PCIe in J7200, the fallback compatible of "ti,j721e-pcie-ep" within the
> AM64's "compatible: contains:" check will match the schema and it will check the
> existing "num-lanes" being described as "const: 1" against the value in J7200's
> PCIe node resulting in a warning. 

What warning? What did you put to contains?

> Therefore, using "contains" will result in
> errors if the check has to be performed for device-tree nodes with fallback
> compatibles. The "items" based approach I have used in this patch ensures that
> the schema matches *only* when both the primary and fallback compatible are
> present in the device-tree node.

Long message, but I don't understand it. Why this binding is different
than all others which rely on contains?

>>> +  - if:
>>> +      properties:
>>> +        compatible:
>>> +          items:
>>> +            - const: ti,j784s4-pcie-ep
>>
>> Why? Previous code was correct.
> 
> Though I used "patience diff", for some reason the addition of
> "ti,j721e-pcie-ep" in the check has been treated as the removal of
> "ti,j784s4-pcie-ep" first followed by adding the same later for generating the
> diff in this patch. The diff above is equivalent to the addition of:

No, why do you change existing code? It is correct.


Best regards,
Krzysztof