Re: [PR 174] dt-bindings: chosen: Add "power-state-change-reason" nvmem property

[Oleksij Rempel <o.rempel@pengutronix.de>]

Hi Rob and Krzysztof,

Following up on dt-schema PR #174 regarding the PSCRR framework. We are
currently stuck in a maintainer deadlock regarding how this framework should
bind to its NVMEM cell, and I need your consensus to proceed.

In the PR [1], Rob noted that /chosen only works if the OS standardizes the
NVMEM values. If the values are platform-specific (requiring a mapping driver),
Rob suggested creating a dedicated DT node akin to reboot-mode or
nvmem-reboot-mode.

However, in my earlier kernel patchsets [2] , Krzysztof explicitly NACKed a
dedicated PSCRR DT node, stating that it represents "OS policy" and a software
abstraction rather than physical hardware. Krzysztof suggested instantiating it
via sysfs/modprobe. I attempted that in v11 , but Greg strongly rejected [3]
the sysfs/module parameter approach as fragile and outdated for the driver
core.

We need a robust way to discover this cell during early boot across full power
cuts. To break this catch-22, could you please agree on one of the following?

- Option A (Dedicated DT node): Permit a dedicated pscrr-nvmem node (or a
compatible string on a fixed-cell) as a valid firmware description contract,
following the precedent of nvmem-reboot-mode.

- Option B (/chosen property): Accept the /chosen phandle approach

I am happy to implement whichever hardware/software binding pattern you both
agree is correct for this edge case.

Best Regards,
Oleksij

[1] https://github.com/devicetree-org/dt-schema/pull/174
[2] https://lore.kernel.org/all/58d24ddc-4e8f-4932-ac37-c9a699d36425@linaro.org/
[3] https://lore.kernel.org/all/2025071631-henna-synthesis-9961@gregkh/ 

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