linux-kernel - Re: [PATCH 2/2] dt-bindings: wireless: ath: Deprecate 'qcom,calibration-variant' property

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Message-ID: <7757501b-2576-4f5d-a16a-40e06f12cb5f@oss.qualcomm.com>
Date: Fri, 14 Nov 2025 09:29:46 -0800
From: Jeff Johnson <jeff.johnson@....qualcomm.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc: Jeff Johnson <jjohnson@...nel.org>,
        Johannes Berg <johannes@...solutions.net>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org, ath10k@...ts.infradead.org,
        ath11k@...ts.infradead.org, devicetree@...r.kernel.org,
        ath12k@...ts.infradead.org,
        Miaoqing Pan <miaoqing.pan@....qualcomm.com>
Subject: Re: [PATCH 2/2] dt-bindings: wireless: ath: Deprecate
 'qcom,calibration-variant' property

On 11/14/2025 3:18 AM, Manivannan Sadhasivam wrote:
> On Fri, Nov 14, 2025 at 12:04:55PM +0100, Krzysztof Kozlowski wrote:
>> On 14/11/2025 12:02, Manivannan Sadhasivam wrote:
>>> On Fri, Nov 14, 2025 at 11:47:25AM +0100, Krzysztof Kozlowski wrote:
>>>> On 14/11/2025 11:22, Manivannan Sadhasivam wrote:
>>>>> On devicetree platforms, ath{10k/11k} drivers rely on the presence of the
>>>>> 'qcom,calibration-variant' property to select the correct calibration data
>>>>> for device variants with colliding IDs.
>>>>>
>>>>> But this property based selection has its own downside that it needs to be
>>>>> added to the devicetree node of the WLAN device, especially for PCI based
>>>>> devices. Currently, the users/vendors are forced to hardcode this property
>>>>> in the PCI device node. If a different device need to be attached to the
>>>>> slot, then the devicetree node also has to be changed. This approach is not
>>>>> scalable and creates a bad user experience.
>>>>>
>>>>> So deprecate this property from WLAN devicetree nodes and let the drivers
>>>>> do the devicetree model based calibration variant lookup using a static
>>>>> table.
>>>>>
>>>>> This also warrants removing the property from examples in the binding.
>>>>>
>>>>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
>>>>> ---
>>>>
>>>> The problem - visible in one of the examples here - is that one board
>>>> has multiple WiFi chips and they use different calibration-variant
>>>> properties. How do you find the right calibration variant for such case
>>>> based on board machine match?
>>>>
>>>
>>> I suspect the legitimacy of the example here. I don't understand how a single
>>> machine can have same devices with 3 different calibration data.
>>
>> Me neither but I am not the domain expert here.
>>
>>>
>>> AFAIU, calibration data is specific to the platform design. And I don't see any
>>> upstream supported devicetree having similar properties.
>> Deprecating these is fine with me, but I would prefer if we get here
>> some clear answers that mentioned case cannot happen. If you are sure of
>> that, please mention it in commit msg.
>>
> 
> I'm pretty sure that this example is wrong. But I will wait for Jeff or other
> ath developers to confirm.

As discussed privately this is a valid example. This is a single-band chip. So
a tri-band router platform will have 3 boards, one that is supporting 2 GHz,
one supporting 5 GHz, and one supporting 6 GHz, and each frequency range will
have different calibration data.

So we still need to support slot-specific configuration in cases where the
slot to board mapping really is fixed in the platform.

/jeff