linux-kernel - Re: [PATCH v4 1/3] dt-bindings: Add beaglecc1352

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Date:   Mon, 11 Sep 2023 08:23:16 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Ayush Singh <ayushdevel1325@...il.com>,
        greybus-dev@...ts.linaro.org
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org,
        Vaishnav M A <vaishnav@...gleboard.org>,
        Jason Kridner <jkridner@...gleboard.org>,
        Nishanth Menon <nm@...com>
Subject: Re: [PATCH v4 1/3] dt-bindings: Add beaglecc1352

On 06/09/2023 18:47, Ayush Singh wrote:
> On 9/4/23 12:44, Krzysztof Kozlowski wrote:
>> On 02/09/2023 20:28, Ayush Singh wrote:
>>> Add DT bindings for BeagleCC1352 co-processor UART.
>> This does not look like UART controller.
>>
>>
>>> Signed-off-by: Ayush Singh <ayushdevel1325@...il.com>
>>> ---
>>>   .../bindings/serial/beaglecc1352.yaml         | 25 +++++++++++++++++++
>> It's not a serial driver. Don't put it in unrelated directory.
>>
>>> @@ -0,0 +1,25 @@
>>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/serial/beaglecc1352.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: BeaglePlay CC1352 serial UART
>> How is this serial UART? Of what? The SoC? Do not describe interface but
>> the device.
>>
>>> +
>>> +maintainers:
>>> +  - Ayush Singh <ayushdevel1325@...il.com>
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: beagle,cc1352
>> No resources? This does not seem useful... Put it then only in trivial
>> devices if your hardware - hardware, not driver - does not have any
>> pins, interrupts or other resources.
>>
>>> +
>>> +required:
>>> +  - compatible
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    beaglecc1352 {
>> Node names should be generic. See also an explanation and list of
>> examples (not exhaustive) in DT specification:
>> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation
>>
>> Best regards,
>> Krzysztof
> 
> I would like to get some help on how to tackle this particular device 
> since I cannot seem to find anything similar to this setup. First let me 
> go over the setup.
> 
> The BeaglePlay board has 2 processors. AM625 processor which is the main 
> processor. This runs the main Linux system. This processor does not have 
> direct access to SubG.
> 
> It also contains a CC1352P7 MCU with it's own flash program memory, ROM 
> and SRAM. This processor has SubG antenna. It runs it's own OS (Zephyr 
> by default).
> 
> The only way for CC1352P7 and AM625 to communicate is by using that 
> particular UART which is just a standard 8250 UART. The setup pretty 
> much looks like 2 boards connected over UART except the UART will always 
> be static.
> 
> I guess it would make most sense to write a CC1352P7 binding in this 
> case? However, I am not sure how accurate that is since anything from 
> the Linux side will be interacting with the Zephyr application, and not 
> the processor. So in all actuality, the processor itself does not matter 
> at all.

I think the bindings require specific name and give you proper hint what
should it be. If you still wonder, it means you still did not test your
DTS. Such testing is a requirement.

Best regards,
Krzysztof