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From: mateusz.nowicki@posteo.net
To: Patrick DELAUNAY <patrick.delaunay@foss.st.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	devicetree@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: dts: st: mark main supplies always-on on stm32mp257f-dk
Date: Thu, 08 Oct 2026 11:43:56 +0000	[thread overview]
Message-ID: <1baaa8cb024104ee6d201d55467f6718@posteo.net> (raw)
In-Reply-To: <aaedc962-63ab-431b-8b27-b4ac9c11d16e@foss.st.com>

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

  reply	other threads:[~2026-10-08 11:44 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-04 11:24 [PATCH] arm64: dts: st: mark main supplies always-on on stm32mp257f-dk Mateusz Nowicki
2026-10-07  9:22 ` Patrick DELAUNAY
2026-10-08 11:43   ` mateusz.nowicki [this message]
2026-10-09  8:17     ` Patrick DELAUNAY
2026-10-09  9:29       ` mateusz.nowicki

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