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

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Message-ID: <kve3f7zkywwsfkylom3jp4e3ejlspnlvnmlkuq77uy6fqsy5dt@gaitvppj2jcw>
Date: Fri, 14 Nov 2025 16:48:32 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
To: 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 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.

- Mani

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