linux-kernel - Re: [PATCH] Eliminate Odroid HC4 power glitches during boot.

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Message-Id: <176889918237.1477585.6813293385956996088.b4-ty@linaro.org>
Date: Tue, 20 Jan 2026 09:53:02 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Kevin Hilman <khilman@...libre.com>, 
 Jerome Brunet <jbrunet@...libre.com>, 
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>, 
 Eric Neulight <Eric.Neulight@...uxdev.slmail.me>
Cc: devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Eliminate Odroid HC4 power glitches during boot.

Hi,

On Fri, 16 Jan 2026 23:02:20 -0500, Eric Neulight wrote:
> Fix issue with Odroid HC4 (and all meson-sm1-odroid) DTS that causes
> regulator power to momentarily glitch OFF-ON during boot.  Add
> regulator-boot-on to all regulator-fixed and regulator-gpio entries
> that (1) define a gpio AND (2) define regulator-always-on.
> 
> U-boot powers on devices necessary for boot then hands off the DTB to
> the kernel.  During probe, linux drivers/regulator/fixed.c and
> gpio-regulator.c both first set the regulator control gpio (that U-boot
> already turned ON) to default OFF before then setting it to the defined
> (ON) state. This glitches the power to the affected devices, unless
> regulator-boot-on is specified with it.  In fact, U-boot has the same
> behavior.  So, during reboot, a power glitch can actually happen twice:
> once when U-boot reads the DTB and probes the gpio and again when the
> kernel reads the DTB and probes the gpio.
> 
> [...]

Thanks, Applied to https://git.kernel.org/pub/scm/linux/kernel/git/amlogic/linux.git (v6.20/arm64-dt)

[1/1] Eliminate Odroid HC4 power glitches during boot.
      https://git.kernel.org/amlogic/c/436418ef5baa024b7b15dd730c36d651c6aaaf47

These changes has been applied on the intermediate git tree [1].

The v6.20/arm64-dt branch will then be sent via a formal Pull Request to the Linux SoC maintainers
for inclusion in their intermediate git branches in order to be sent to Linus during
the next merge window, or sooner if it's a set of fixes.

In the cases of fixes, those will be merged in the current release candidate
kernel and as soon they appear on the Linux master branch they will be
backported to the previous Stable and Long-Stable kernels [2].

The intermediate git branches are merged daily in the linux-next tree [3],
people are encouraged testing these pre-release kernels and report issues on the
relevant mailing-lists.

If problems are discovered on those changes, please submit a signed-off-by revert
patch followed by a corrective changeset.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/amlogic/linux.git
[2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
[3] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

-- 
Neil