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

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

On 12/03/2024 16:58, Trilok Soni wrote:
> On 3/12/2024 9:52 AM, Nikunj Kela wrote:
>>> One is with old firmware interface and -scmi is with SCMI. No new top
>>> level compatible change is needed. I understand it was switch from one
>>> interface to the another and not like Qcom platforms which is moving
>>> from in-kernel solution to firmware solution. But the general rule applies
>>> here as well unless there are specific reasons for needing that exception.
>>> I am not against it or ruling that out, just curious to understand them.
>>>
>>> -- 
>>> Regards,
>>> Sudeep
>>
>> Hi All,
>>
>> Thank you all for all your inputs on this. I discussed this with Srini and he suggested that we could use a new optional DT property like "qcom, fw-managed" to ascertain if we are running on firmware managed variant. Thus each device node in the dts can add this. I did ask him if, instead of putting it to each device node, we can use it at the board level however he thinks that it would not be easy to update yaml documentation on DT nodes with board level property. So if everyone here agrees with this approach, I would like to close this thread.
>>
>> Thank you!
> 
> Is "fw-managed" name restricted to SCMI based approaches? Why it needs to be per
> driver device-tree node? 

This makes it much more explicit in device bindings on the resource 
dependencies.

What happens when I attach the same SOC-IP
> along w/ the RISC-V Application core and use the RPMI?
> 
> Should not have fw-managed defined at the devicetree spec? This is not a
> ARM specific problem since the drivers which are going to use this flag/property
> are generic shouldn't care about SCMI/RPMI.
> 

> Basically, I would prefer better than "qcom, fw-managed" since this is not
> a qcom specific problem.


We already have something like this in mainline where the BAM DMA 
controller is remotely powered.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml?h=v6.8


--srini

>