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

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Date:   Thu, 5 May 2022 15:11:09 +0200
From:   Hakan Jansson <hakan.jansson@...ineon.com>
To:     Linus Walleij <linus.walleij@...aro.org>
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>,
        <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 1/2] dt-bindings: net: broadcom-bluetooth: Add property
 for autobaud mode

Hi Linus,

Thanks for responding.

On 5/5/2022 12:15 AM, Linus Walleij wrote:
> On Wed, May 4, 2022 at 11:04 AM Hakan Jansson
> <hakan.jansson@...ineon.com> wrote:
>
>> +  brcm,uses-autobaud-mode:
>> +    type: boolean
>> +    description: >
>> +      The controller should be started in autobaud mode by asserting
>> +      BT_UART_CTS_N (i.e. host RTS) during startup. Only HCI commands supported
>> +      in autobaud mode should be used until patch FW has been loaded.
> Things like gnss uses the current-speed attribute to set a serial link speed,
> maybe also Bluetooth?
As far as I can tell, not many Bluetooth drivers use the current-speed 
attribute yet but perhaps it would be a good idea to start using it more 
broadly in the future to set the initial serial link speed.

>
> Would it make sense to use
>
> current-speed-auto;
>
> As a flag for these things in general?
I suppose a general flag could be useful but to be honest I don't know 
if any other devices besides the ones using the Broadcom driver has any 
use for it. You would probably also still want to be able to use 
current-speed to set the link speed and end up using both 
current-speed=x and current-speed-auto at the same time, which might 
look a little confusing?

Please let me know if you'd still prefer "current-speed-auto" over 
"brcm,uses-autobaud-mode" and I'll revise the patch and rename it!

>
> Yours,
> Linus Walleij

Thanks,
Håkan