linux-kernel - Re: [PATCH v2] regulator: core: Resolve supply name earlier to prevent double-init

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Date:   Fri, 28 Oct 2022 18:59:36 +0200
From:   Christian Kohlschütter 
        <christian@...lschutter.com>
To:     Mark Brown <broonie@...nel.org>,
        Robin Murphy <robin.murphy@....com>
Cc:     wens@...nel.org, Heiko Stübner <heiko@...ech.de>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Linux MMC List <linux-mmc@...r.kernel.org>,
        Markus Reichl <m.reichl@...etechno.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] regulator: core: Resolve supply name earlier to
 prevent double-init

> On 18. Aug 2022, at 17:22, Mark Brown <broonie@...nel.org> wrote:
> 
> On Fri, 22 Jul 2022 19:42:27 +0200, Christian Kohlschütter wrote:
>> Previously, an unresolved regulator supply reference upon calling
>> regulator_register on an always-on or boot-on regulator caused
>> set_machine_constraints to be called twice.
>> 
>> This in turn may initialize the regulator twice, leading to voltage
>> glitches that are timing-dependent. A simple, unrelated configuration
>> change may be enough to hide this problem, only to be surfaced by
>> chance.
>> 
>> [...]
> 
> Applied to
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git for-next
> 
> Thanks!
> 
> [1/1] regulator: core: Resolve supply name earlier to prevent double-init
>    commit: 8a866d527ac0441c0eb14a991fa11358b476b11d
> 
> All being well this means that it will be integrated into the linux-next
> tree (usually sometime in the next 24 hours) and sent to Linus during
> the next merge window (or sooner if it is a bug fix), however if
> problems are discovered then the patch may be dropped or reverted.
> 
> You may get further e-mails resulting from automated or manual testing
> and review of the tree, please engage with people reporting problems and
> send followup patches addressing any issues that are reported if needed.
> 
> If any updates are required or you are submitting further changes they
> should be sent as incremental updates against current git, existing
> patches will not be replaced.
> 
> Please add any relevant lists and maintainers to the CCs when replying
> to this mail.
> 
> Thanks,
> Mark

I've finally managed to publish a blog post about this journey into regulator land; I hope you find it worthwhile.
https://kohlschuetter.github.io/blog/posts/2022/10/28/linux-nanopi-r4s/

Thanks to everybody involved for getting this far!
Special thanks go to Robin Murphy for pulling out the oscillator, and Mark Brown for helping that these changes get into 6.1.

Best,
Christian