linux-kernel - Re: [RFC PATCH 2/2] mfd: syscon: allow reset control for syscon devices

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Date:   Tue, 06 Dec 2022 15:18:23 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Philipp Zabel" <p.zabel@...gutronix.de>,
        "Jeremy Kerr" <jk@...econstruct.com.au>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Lee Jones" <lee@...nel.org>, "Rob Herring" <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: [RFC PATCH 2/2] mfd: syscon: allow reset control for syscon devices

On Tue, Dec 6, 2022, at 10:25, Philipp Zabel wrote:
> On Di, 2022-12-06 at 09:41 +0100, Arnd Bergmann wrote:
>> Philipp, what is the earliest point at which
>> reset_controller_register() can be called? Is that
>> possible before postcore_initcall() or driver_register()?
>
> reset_controller_register() only initializes a few fields in the passed
> rcdev structure and adds it to a static list under a static mutex, so
> there's not much of a limit.

Ok, in that case I think we should at least leave the option of
doing the reset from an early syscon as well.

> However, reset controllers that choose to register early without
> creating a platform device may run into issues with devlink inhibiting
> reset consumers' probe [1].

Right. I think the is generally a problem of "early" code, so
device drivers should avoid doing this if at all possible, but at
the same time it makes sense for infrastructure to tolerate drivers
doing it.

     Arnd