linux-kernel - Re: [PATCH hyperv-next v5 07/11] dt-bindings: microsoft,vmbus: Add interrupts and DMA coherence

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Message-ID: <c7f9d861-f617-4064-8c98-2ace06e9c25e@linux.microsoft.com>
Date: Mon, 10 Mar 2025 10:05:56 -0700
From: Roman Kisel <romank@...ux.microsoft.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: arnd@...db.de, bhelgaas@...gle.com, bp@...en8.de,
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Subject: Re: [PATCH hyperv-next v5 07/11] dt-bindings: microsoft,vmbus: Add
 interrupts and DMA coherence



On 3/10/2025 2:28 AM, Krzysztof Kozlowski wrote:
> On Fri, Mar 07, 2025 at 02:02:59PM -0800, Roman Kisel wrote:
>> To boot on ARM64, VMBus requires configuring interrupts. Missing
>> DMA coherence property is sub-optimal as the VMBus transations are
>> cache-coherent.
>>
>> Add interrupts to be able to boot on ARM64. Add DMA coherence to
>> avoid doing extra work on maintaining caches on ARM64.
> 
> How do you add it?
> 

I added properties to the node. Should I fix the description, or I am
misunderstanding the question?

>>
>> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
>> ---
>>   .../devicetree/bindings/bus/microsoft,vmbus.yaml          | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml b/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
>> index a8d40c766dcd..3ab7d0116626 100644
>> --- a/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
>> +++ b/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
>> @@ -28,13 +28,16 @@ properties:
>>   required:
>>     - compatible
>>     - ranges
>> +  - interrupts
>>     - '#address-cells'
>>     - '#size-cells'
>>   
>> -additionalProperties: false
>> +additionalProperties: true
> 
> This is neither explained in commit msg nor correct.
> 

Not explained, as there is no good explanation as described below.

> Drop the change. You cannot have device bindings ending with 'true'
> here - see talks, example-bindings, writing-schema and whatever resource
> is there.
> 

Thanks, I'll put more effort into bringing this into a better form!
If you have time, could you comment on the below?

The Documentation says

   * additionalProperties: true
     Rare case, used for schemas implementing common set of properties.
Such schemas are supposed to be referenced by other schemas, which then 
use 'unevaluatedProperties: false'.  Typically bus or common-part schemas.

This is a bus so I added that line to the YAML, and I saw it in many
other YAML files. Without that line, there was a warning from the local
DT validation described in the Documentation about not having pin
controls which was weird, and adding

"additionalProperties: true"

fixed the warnings (didn't debug much though). As a side note, there was
a similar warning coming from another YAML during running DT schema
validation as described in the Documentation so maybe warnings are fine.

> Best regards,
> Krzysztof
> 

-- 
Thank you,
Roman