linux-kernel - Re: [PATCH v2 1/2] dt-bindings: net: bluetooth: Add MediaTek MT7921S SDIO Bluetooth

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Date: Tue, 30 Jan 2024 08:37:15 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Chen-Yu Tsai <wenst@...omium.org>
Cc: Marcel Holtmann <marcel@...tmann.org>,
 Luiz Augusto von Dentz <luiz.dentz@...il.com>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Matthias Brugger
 <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Sean Wang <sean.wang@...iatek.com>, linux-bluetooth@...r.kernel.org,
 netdev@...r.kernel.org, linux-mediatek@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: net: bluetooth: Add MediaTek MT7921S
 SDIO Bluetooth

On 30/01/2024 04:32, Chen-Yu Tsai wrote:
> On Mon, Jan 29, 2024 at 3:34 PM Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
>>
>> On 29/01/2024 04:38, Chen-Yu Tsai wrote:
>>
>>>>> +allOf:
>>>>> +  - $ref: bluetooth-controller.yaml#
>>>>> +
>>>>> +properties:
>>>>> +  compatible:
>>>>> +    enum:
>>>>> +      - mediatek,mt7921s-bluetooth
>>>>
>>>> Can it be also WiFi on separate bus? How many device nodes do you need
>>>> for this device?
>>>
>>> For the "S" variant, WiFi is also on SDIO. For the other two variants,
>>> "U" and "E", WiFi goes over USB and PCIe respectively. On both those
>>> variants, Bluetooth can either go over USB or UART. That is what I
>>> gathered from the pinouts. There are a dozen GPIO pins which don't
>>> have detailed descriptions though. If you want a comprehensive
>>> binding of the whole chip and all its variants, I suggest we ask
>>> MediaTek to provide it instead. My goal with the binding is to document
>>> existing usage and allow me to upstream new device trees.
>>>
>>> For now we only need the Bluetooth node. The WiFi part is perfectly
>>> detectable, and the driver doesn't seem to need the WiFi reset pin.
>>> The Bluetooth driver only uses its reset pin to reset a hung controller.
>>
>> Then suffix "bluetooth" seems redundant.
> 
> I think keeping the suffix makes more sense though. The chip is a two
> function piece, and this only targets one of the functions. Also, the

That's why I asked and you said there is only one interface: SDIO.

> compatible string is already used in an existing driver [1] and
> soon-to-be in-tree device tree [2].

That's not the way to upstream compatible. You cannot send it bypassing
bindings and review and later claim that's an ABI.


Best regards,
Krzysztof