Re: DT Query on "New Compatible vs New Property"

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On 14/12/2023 07:17, Manivannan Sadhasivam wrote:
> On Tue, Dec 12, 2023 at 11:06:42AM -0800, Nikunj Kela wrote:
>> + Linaro team
>>
>> On 12/12/2023 11:01 AM, Krzysztof Kozlowski wrote:
>>> On 12/12/2023 18:45, Nikunj Kela wrote:
>>>> We are abstracting some resources(ex. clocks) under new firmware on an
>>>> existing platform therefore need to make changes in certain drivers to
>>>> work with that firmware. We need to make a distinction between two
>>>> different variants of the FW. In one case, some resources will be
>>>> abstracted while in other case, they won't be abstracted. My query is -
>>>> "should we define a new compatible string for the variant with
>>>> abstracted resources(in FW) or we should add a new DT property keeping
>>>> the compatible same?"
>>> Hi,
>>>
>>> Usually change in the interface or behavior warrants new compatible.
>>> Property would be suitable if the same device, e.g. same SoC component
>>> with same FW, was configured differently on different boards.
>>>
> 
> Here, the hardware is going to be the same, but the resources (clocks,
> regulators, etc...) will be controlled by the firmware instead of OS.

Yeah, that's the problem with generic questions, instead of specific...
"Talk is cheap."

OK, so the hardware is exactly the same? Does FW bring any
incompatibilities in the interface or is it just about the clocks? I
guess I should not have included "with same FW" in my last statement.
It's true, but way too narrow. Therefore let me rephrase it:

"Property would be suitable if the same device, e.g. same SoC component
with same interface towards OS, was configured differently on different
boards."

> 
> Should we still use a different compatible? For the similar usecase, we already
> have properties like 'qcom,controlled-remotely' to let the OS know that it
> should not configure the hardware and just consume it.

Yeah, also similar qcom,gsi-loader.

Best regards,
Krzysztof





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