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

Raj Kumar Bhagat
2024-10-23T12:22:26Z

On 10/23/2024 12:08 PM, Krzysztof Kozlowski wrote:
> On 23/10/2024 08:03, Raj Kumar Bhagat wrote:
>> QCN9274 device has WSI support. WSI stands for WLAN Serial Interface.
>> It is used for the exchange of specific control information across
>> radios based on the doorbell mechanism. This WSI connection is
>> essential to exchange control information among these devices
>>
>> Hence, describe WSI interface supported in QCN9274 with the following
>> properties:
>>
>> - qcom,wsi-group-id: It represents the identifier assigned to the WSI
>> connection. All the ath12k devices connected to same WSI connection
>> have the same wsi-group-id.
>>
>> - qcom,wsi-index: It represents the identifier assigned to ath12k
>> device in the order of the WSI connection.
>>
>> - qcom,wsi-num-devices: Number of devices connected through WSI in
>> the same group ID.
>
> You should have separate binding.
>

Based on the discussion in previous patch [1/6]. If required we will have
separate binding.

>>
>> Signed-off-by: Raj Kumar Bhagat <quic_rajkbhag@quicinc.com>
>> ---
>> .../bindings/net/wireless/qcom,ath12k.yaml | 61 +++++++++++++++++++
>> 1 file changed, 61 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/net/wireless/qcom,ath12k.yaml b/Documentation/devicetree/bindings/net/wireless/qcom,ath12k.yaml
>> index ecf38af747f7..6c8f97865075 100644
>> --- a/Documentation/devicetree/bindings/net/wireless/qcom,ath12k.yaml
>> +++ b/Documentation/devicetree/bindings/net/wireless/qcom,ath12k.yaml
>> @@ -19,6 +19,7 @@ properties:
>> compatible:
>> enum:
>> - pci17cb,1107 # WCN7850
>> + - pci17cb,1109 # QCN9274
>>
>> reg:
>> maxItems: 1
>> @@ -50,6 +51,41 @@ properties:
>> vddpcie1p8-supply:
>> description: VDD_PCIE_1P8 supply regulator handle
>>
>> + wsi:
>> + type: object
>> + description:
>> + The ath12k devices (QCN9274) feature WSI support. WSI stands for
>> + WLAN Serial Interface. It is used for the exchange of specific
>> + control information across radios based on the doorbell mechanism.
>> + This WSI connection is essential to exchange control information
>> + among these devices.
>> +
>> + properties:
>> + qcom,wsi-group-id:
>> + $ref: /schemas/types.yaml#/definitions/uint32
>> + description:
>> + It represents the identifier assigned to the WSI connection. All
>> + the ath12k devices connected to same WSI connection have the
>> + same wsi-group-id.
>
> Why it cannot be implied by compatible?
>
>> +
>> + qcom,wsi-index:
>> + $ref: /schemas/types.yaml#/definitions/uint32
>> + description:
>> + It represents the identifier assigned to ath12k device in the
>> + order of the WSI connection.
>
> No, we do not have indices in DTS.
>
>> +
>> + qcom,wsi-num-devices:
>> + $ref: /schemas/types.yaml#/definitions/uint32
>> + description:
>> + Number of devices connected through WSI in the same group ID.
>
> Wait, why? Number of devices is visible from DTS. You are missing some
> diagram showing this but it looks like you stuff multiple nodes into one
> node.
>
>

To discuss the above comments, let me provide a diagram that is part of the
commit log of DTS patch [6/6].

The WSI connection in RDP433 is represented below:

+-------+ +-------+ +-------+
| pcie2 | | pcie3 | | pcie1 |
| | | | | |
+----->| wsi |------->| wsi |------->| wsi |-----+
| | idx 0 | | idx 1 | | idx 2 | |
| +-------+ +-------+ +-------+ |
+------------------------------------------------------+

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.

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.

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.

>
>> +
>> + required:
>> + - qcom,wsi-group-id
>> + - qcom,wsi-index
>> + - qcom,wsi-num-devices
>> +
>> + additionalProperties: false
>> +
>> required:
>> - compatible
>> - reg
>> @@ -108,3 +144,28 @@ examples:
>> };
>> };
>> };
>> +
>> + - |
>> + pcie {
>> + #address-cells = <3>;
>> + #size-cells = <2>;
>> +
>> + pcie@0 {
>> + device_type = "pci";
>> + reg = <0x0 0x0 0x0 0x0 0x0>;
>> + #address-cells = <3>;
>> + #size-cells = <2>;
>> + ranges;
>> +
>> + wifi@0 {
>> + compatible = "pci17cb,1109";
>> + reg = <0x0 0x0 0x0 0x0 0x0>;
>> +
>> + wsi {
>> + qcom,wsi-group-id = <0>;
>> + qcom,wsi-index = <0>;
>> + qcom,wsi-num-devices = <3>;
>
> So what are the other 2 devices? Where are they documented?
>

In the example, we have represented only one WiFi node. Although it indicates
that there are a total of three devices in the same WSI connection with group-id
0, we can add all three WiFi nodes in the next version if required.