linux-kernel - Re: [PATCH v2 1/2] dt-bindings: net: broadcom-bluetooth: Add property for autobaud mode

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Date:   Sun, 22 May 2022 10:14:02 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Hakan Jansson <hakan.jansson@...ineon.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        linux-bluetooth@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: net: broadcom-bluetooth: Add property
 for autobaud mode

On 20/05/2022 17:07, Hakan Jansson wrote:
> Some devices (e.g. CYW5557x) require autobaud mode to enable FW loading.

Which devices support this? You probably need allOf:if:then.

> Autobaud mode can also be required on some boards where the controller
> device is using a non-standard baud rate when first powered on.
> 
> This patch adds a property, "brcm,uses-autobaud-mode", to enable autobaud
> mode selection.

Don't use "This patch":
https://elixir.bootlin.com/linux/v5.17.1/source/Documentation/process/submitting-patches.rst#L95

> 
> Signed-off-by: Hakan Jansson <hakan.jansson@...ineon.com>
> ---
> V1 -> V2: Modify property description
> 
>  .../devicetree/bindings/net/broadcom-bluetooth.yaml      | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/broadcom-bluetooth.yaml b/Documentation/devicetree/bindings/net/broadcom-bluetooth.yaml
> index 5aac094fd217..a29f059c21cc 100644
> --- a/Documentation/devicetree/bindings/net/broadcom-bluetooth.yaml
> +++ b/Documentation/devicetree/bindings/net/broadcom-bluetooth.yaml
> @@ -92,6 +92,15 @@ properties:
>         pcm-sync-mode: slave, master
>         pcm-clock-mode: slave, master
>  
> +  brcm,uses-autobaud-mode:

Based on description, I understand the host triggers using autobaud.
However here you word it as "uses", so it is independent of host, it
looks like property of a device. The commit msg describes it even
different - "require autobaud".

This leads to second issue - it looks like there is some hardware
property (requiring to use autobaud) which should be described by
bindings. But instead you describe desired operational feature.

> +    type: boolean
> +    description: >

No need for '>'.

> +      Setting this property will make the host (driver) assert the controller
> +      chip's BT_UART_CTS_N prior to asserting BT_REG_ON. This will make the
> +      controller start up in autobaud mode. The controller will then detect the
> +      baud rate of the first incoming (HCI Reset) command from the host and
> +      subsequently use that baud rate.
> +
>    interrupts:
>      items:
>        - description: Handle to the line HOST_WAKE used to wake


Best regards,
Krzysztof