linux-kernel - Re: [PATCH v6] dt-bindings: net: mediatek,mt7925-bluetooth.yaml

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Message-ID: <cb03b137-c87c-446f-a6c6-45b6656af212@kernel.org>
Date: Tue, 8 Jul 2025 08:05:00 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Zhangchao Zhang <ot_zhangchao.zhang@...iatek.com>,
 Marcel Holtmann <marcel@...tmann.org>,
 Matthias Brugger <matthias.bgg@...il.com>,
 Luiz Von Dentz <luiz.dentz@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: Sean Wang <sean.wang@...iatek.com>, Jiande Lu <jiande.lu@...iatek.com>,
 Deren Wu <deren.Wu@...iatek.com>, Chris Lu <chris.lu@...iatek.com>,
 Hao Qin <Hao.qin@...iatek.com>, Wallace Yu <Wallace.Yu@...iatek.com>,
 linux-bluetooth <linux-bluetooth@...r.kernel.org>,
 linux-kernel <linux-kernel@...r.kernel.org>,
 linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
 linux-mediatek <linux-mediatek@...ts.infradead.org>,
 devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH v6] dt-bindings: net: mediatek,mt7925-bluetooth.yaml

On 08/07/2025 08:01, Zhangchao Zhang wrote:
> Reset BT via BT_KILL_1V2_L hardware pin.
> 
> On the M.2 standard hardware pin interface, the MTK chip
> has a pin called BT_KILL_1V2_L or W_DISABLE#2, it uses
> function-level device reset (FLDR) to reset Bluetooth.
> When it is pulled low, it can external shut down the BT
> function, it is defined as 5 on the MT7925 chip, and is
> defined as 248 on the device tree pio controller.
> 
> Signed-off-by: Zhangchao Zhang <ot_zhangchao.zhang@...iatek.com>
> ---
>  .../bluetooth/mediatek,mt7925-bluetooth.yaml  | 55 +++++++++++++++++++
>  MAINTAINERS                                   |  1 +
>  2 files changed, 56 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/net/bluetooth/mediatek,mt7925-bluetooth.yaml
> 
> diff --git a/Documentation/devicetree/bindings/net/bluetooth/mediatek,mt7925-bluetooth.yaml b/Documentation/devicetree/bindings/net/bluetooth/mediatek,mt7925-bluetooth.yaml
> new file mode 100644
> index 000000000000..636b8b3d6a14
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/bluetooth/mediatek,mt7925-bluetooth.yaml
> @@ -0,0 +1,55 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/net/bluetooth/mediatek,mt7925-bluetooth.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Bluetooth mediatek use BT_KILL_1V2_L hardware pin to reset BT
> +
> +maintainers:
> +  - Sean Wang <sean.wang@...iatek.com>
> +
> +description:
> +  MT7925 chip uses the USB bus to communicate with the host.
> +  Two methods are used to reset Bluetooth. It provide hardware
> +  pin, when an exception occurs, resetting Bluetooth by hardware
> +  pin is more stable than resetting Bluetooth by software. If the
> +  corresponding pin is not found in dts, bluetooth can also be
> +  reset successfully.

Don't describe DTS, but the hardware.

> +
> +allOf:
> +  - $ref: bluetooth-controller.yaml#
> +
> +properties:
> +  compatible:
> +    enum:
> +      - mediatek,mt7925-bluetooth
> +
> +  "#gpio-cells":
> +    const: 2

You did not say this is a GPIO controller.

> +
> +  reset-gpios:
> +    maxItems: 1
> +    description:
> +      Default high level, this pin can external shut down the BT function

How defaults matter?

> +      when this pin is pull low, at the same time, USB interface will be also
> +      disabled. When this function is not required, external pull high is not

So active low?

> +      required. After 200ms, it is pulled high to 3.3v and the next probe is
> +      performed. On typical M.2 key E modules this is the W_DISABLE2# pin.

So that's part of PCI slot? Sorry, but this does not fit here at all.


Best regards,
Krzysztof