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

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Message-ID: <1703d8d7-5105-4585-b8f0-82bb54809718@kernel.org>
Date: Fri, 14 Nov 2025 12:04:55 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
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 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.


Best regards,
Krzysztof