Re: [PATCH] arm64: dts: st: mark main supplies always-on on stm32mp257f-dk

[mateusz . nowicki]

Hi Patrick,

On 07.10.2026 11:22, Patrick DELAUNAY wrote:
> For STMicroelectronics boards, the STPMIC always-on regulator are
> managed on SCMI server side in OP-TEE.
>
> So no need to manage this constraint in Linux device tree.
>
> This always-on  regulator are exposed only for information or to be
> used are supply for some IP.

Thanks, that makes sense. OP-TEE keeps these rails on no matter what
Linux asks for, and the board keeps running fine.

The part I found confusing is what Linux reports. Since nothing in
Linux uses these regulators, the regulator core turns them off about
30 seconds after boot:

   [   31.713597] v1v8: disabling
   [   31.716454] v3v3: disabling

The SCMI call succeeds, so from then on regulator_summary shows
vddcore, v1v8 and v3v3 with a use count of 0, as if they were off.
In reality they are still powered.

With regulator-always-on, what Linux shows matches the hardware.
Would you still prefer to keep it out of the board DT? If so, I'm
happy to drop the patch.

Thanks,
Mateusz