Re: [PATCH v4 2/2] dt-bindings: dma: HiSilicon: Add bindings for HiSilicon Ascend sdma

["guomengqi (A)" <guomengqi3@huawei.com>]

在 2023/9/13 17:20, Krzysztof Kozlowski 写道:
> On 13/09/2023 10:28, Guo Mengqi wrote:
>> Add device-tree binding documentation for sdma hardware on
>> HiSilicon Ascend SoC families.
>>
>> Signed-off-by: Guo Mengqi <guomengqi3@huawei.com>
>> ---
>>
>> +  dma-channel-mask:
>> +    minItems: 1
>> +    maxItems: 2
> Why 2? Care to bring any example? Where is your DTS?

Seems that the complete dts is not in the repository.

Some platform supports up to 40 channels at most, in design. So I think 
2 should be enough.

>> +  iommus:
>> +    maxItems: 1
>> +
>> +  pasid-num-bits:
>> +    description: |
>> +      This tells smmu that this device supports iommu-sva feature.
>> +      This determines the maximum number of digits in the pasid.
>> +    maximum: 0x10
>> +
>> +  dma-coherent: true
>> +
>> +  dma-can-stall: true
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - dma-channel-mask
>> +  - '#dma-cells'
>> +  - iommus
>> +  - pasid-num-bits
>> +  - dma-can-stall
> I am not sure if requiring dma-can-stall is correct here. To my
> understanding this is in general optional property.

If  "dma-can-stall" is declared,  drivers can rely on smmu to handle 
page-fault.

Yes, this is not a required one. It does not affect main usage. Drop it 
in next patch.

> Best regards,
> Krzysztof
>
>
> .

Best regards,

Guo Mengqi