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

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Date: Mon, 29 Jan 2024 11:38:49 +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 Fri, Jan 26, 2024 at 6:40 PM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 26/01/2024 07:34, Chen-Yu Tsai wrote:
> > The MediaTek MT7921S is a WiFi/Bluetooth combo chip that works over
> > SDIO. While the Bluetooth function is fully discoverable, the chip
> > has a pin that can reset just the Bluetooth side, as opposed to the
> > full chip. This needs to be described in the device tree.
> >
> > Add a device tree binding for MT7921S Bluetooth over SDIO specifically
> > ot document the reset line.
>
> s/ot/to/
>
> >
> > Cc: Sean Wang <sean.wang@...iatek.com>
> > Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
> > ---
> > Changes since v1:
> > - Reworded descriptions
> > - Moved binding maintainer section before description
> > - Added missing reference to bluetooth-controller.yaml
> > - Added missing GPIO header to example
> >
> >  .../bluetooth/mediatek,mt7921s-bluetooth.yaml | 53 +++++++++++++++++++
> >  MAINTAINERS                                   |  1 +
> >  2 files changed, 54 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/net/bluetooth/mediatek,mt7921s-bluetooth.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/net/bluetooth/mediatek,mt7921s-bluetooth.yaml b/Documentation/devicetree/bindings/net/bluetooth/mediatek,mt7921s-bluetooth.yaml
> > new file mode 100644
> > index 000000000000..ff11c95c816c
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/net/bluetooth/mediatek,mt7921s-bluetooth.yaml
> > @@ -0,0 +1,53 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/net/bluetooth/mediatek,mt7921s-bluetooth.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: MediaTek MT7921S Bluetooth
> > +
> > +maintainers:
> > +  - Sean Wang <sean.wang@...iatek.com>
> > +
> > +description:
> > +  MT7921S is an SDIO-attached dual-radio WiFi+Bluetooth Combo chip; each
> > +  function is its own SDIO function on a shared SDIO interface. The chip
> > +  has two dedicated reset lines, one for each function core.
> > +  This binding only covers the Bluetooth part of the chip.
> > +
> > +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.

> Missing blank line.

Will fix.

> > +  reg:
> > +    const: 2
> > +
> > +  reset-gpios:
> > +    maxItems: 1
> > +    description:
> > +      An active-low reset line for the Bluetooth core; on typical M.2
> > +      key E modules this is the W_DISABLE2# pin.
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +
> > +additionalProperties: false
>
> Instead 'unevaluatedProperties: false'

Will fix.


Thanks
ChenYu