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

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Message-ID: <CAGXv+5HxXzjigN3Bp96vkv71WfTJ1S2b7Wgafc4GxLmhu6+jMg@mail.gmail.com>
Date: Tue, 30 Jan 2024 11:32:09 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.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 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
compatible string is already used in an existing driver [1] and
soon-to-be in-tree device tree [2].


ChenYu

[1] https://elixir.bootlin.com/linux/latest/source/drivers/bluetooth/btmtksdio.c#L1414
[2] https://elixir.bootlin.com/linux/v6.8-rc1/source/arch/arm64/boot/dts/mediatek/mt8183-kukui-jacuzzi-pico6.dts#L86