Re: [RFC PATCH 2/6] dt-bindings: net: wireless: ath12k: describe WSI property for QCN9274

Raj Kumar Bhagat
2024-10-25T10:08:30Z

On 10/23/2024 11:27 PM, Krzysztof Kozlowski wrote:
> On 23/10/2024 14:22, Raj Kumar Bhagat wrote:
>> The above three blocks represent the QCN9274 WiFi devices connected to their
>> respective PCI slots. The dotted line represents the WSI connection that connects
>> these three devices together. Hence, the WSI interface is part of the QCN9274 device.
>>
>> To describe this WSI hardware connection in the device tree, we are adding three
>> properties inside the WSI object:
>>
>> 1. qcom,wsi-group-id:
>> In the above diagram, we have one WSI connection connecting all three devices.
>> Hence, “qcom,wsi-group-id” for all three devices can be 0.
>>
>> This cannot be implied by the compatible property, as explained below:
>> Let’s take the case of a platform that can have four QCN9274 WiFi devices. Below
>> is one possibility of a WSI connection:
>>
>> +-------+ +-------+ +-------+ +-------+
>> | pcie2 | | pcie3 | | pcie1 | | pcie0 |
>> | | | | | | | |
>> +---->| wsi |------>| wsi |--+ +-->| wsi |----->| wsi |----+
>> | | idx 0 | | idx 1 | | | | idx 0 | | idx 1 | |
>> | +-------+ +-------+ | | +-------+ +-------+ |
>> +--------------------------------+ +-------------------------------+
>>
>> In this case, QCN9274 devices connected in PCIe2 and PCIe3 will have the same
>> “qcom,wsi-group-id”. This group-id will be different from the “qcom,wsi-group-id”
>> of QCN9274 devices connected at PCIe1 and PCIe0.
> Thanks, this explains why group-id cannot be same...
>
>> 2. qcom,wsi-index:
>> This is a unique identifier of the device within the same group. The value of
>> wsi-idx is represented in both the above cases (RDP433 and the 4 WiFi device
>> platform) in the diagram itself.
> But still any device-indexing is in general not accepted (and was
> mentioned during reviews multiple times).
>
> This looks like circular list, so phandle will be enough. You only need
> to mark devices being part of the same chain.
>
> Actually graph with endpoints would be more suitable, assuming above
> diagram represents connections.
>

Thanks for suggesting "graph will endpoints" approach for representing WSI
connections.

I will check on this and come back.

> Please include that diagram in binding description.
>

Sure will include the above diagram in next version.

>> 3. qcom,wsi-num-devices:
>> Represents the number of devices connected through WSI within the same WSI group to
>> which the device belongs.
>>
>> In the case of RDP433, all devices will have this number as 3.
>> For the second example with four WiFi devices but with two WSI connections, the
>> value of “qcom,wsi-num-devices” for each device will be 2.
> Not needed, just iterate over the graph children.

Thanks, based on "graph with endpoints" implementation will have this as well.