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SubjectRe: [PATCH v2 1/2] dt-bindings: net: broadcom-bluetooth: Add property for autobaud mode
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On 23/05/2022 11:21, Hakan Jansson wrote:
> Hi Krzysztof,
>
> Thanks for responding.
>
> On 5/22/2022 10:14 AM, Krzysztof Kozlowski wrote:
>>> Some devices (e.g. CYW5557x) require autobaud mode to enable FW loading.
>> Which devices support this? You probably need allOf:if:then.
>
> Most devices _support_ autobaud mode but I don't have a definitive list.
> The CYW5557x is the first device family to _require_ autobaud mode for
> FW loading as far as I know.
>
>>> 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
>
> Sorry, will change in next rev.
>
>>> Signed-off-by: Hakan Jansson <hakan.jansson@infineon.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.
>
> Correct, 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.
>
> I've been thinking of it as a a property of a specific board HW,
> inherited either from a property of the device being used or from a
> property of the HW design (e.g. a PCB using an alternate crystal
> frequency yielding a non-standard baud rate).
>
>> The commit msg describes it even
>> different - "require autobaud".
>
> Yes, the commit message describes two separate reasons why autobaud mode
> would be required:
>
> 1. Requirement coming from Device: "Some devices (e.g. CYW5557x) require
> autobaud mode to enable FW loading."
>
> 2. Requirement coming from HW design: "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 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.
>
> Sorry about that. I've really been struggling with what should go into
> the description. Any suggestions or hints would be much appreciated.
>
> How about, changing the property name to "brcm,requires-autobaud-mode"
> and the description to:
> "Set this property if autobaud mode is required. Autobaud mode is
> required if the device's baud rate in normal mode is not supported by
> the host or if the device requires autobaud mode startup before loading FW."
>
> Would that be an appropriate name and description?

Yes, sounds good. I also have trouble to name it nicely.

Sorry for late reply.

Best regards,
Krzysztof

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