linux-kernel - Re: [PATCH 2/2] regulator: core: Replace _regulator_enable

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Date:   Wed, 20 Apr 2022 22:11:57 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] regulator: core: Replace _regulator_enable_delay()
 with fsleep()

On Wed, Apr 20, 2022 at 11:24:08AM -0700, Brian Norris wrote:
> On Wed, Apr 20, 2022 at 05:28:46PM +0100, Mark Brown wrote:

> > Did the issue with the delay functions preferring delays on the higher
> > end of the allowed range get fixed?  That might be an issue for larger
> > usleep() values.

> Hmm, good question. I had a faint memory of this problem, and searching
> around, I couldn't find that anybody *thought* they fixed it, and I
> found evidence to the contrary (some reports complaining about, e.g.,
> boot-time performance issues in drivers/usb due to the same, with no
> indication that anybody truly fixed the problem).

That's what I feared :/

> So maybe it's better to retain the regulator core helper
> (_regulator_enable_delay()) and rename/repurpose it for my patch 1?

Sounds like a plan.

> I feel like there's some room for improvement in either fsleep() or
> usleep_range() or both, but I'm not sure exactly how to go about that
> right now.

It's really difficult to design an API that's both tasteful and clear
about intent - it's relatively easy for something like a driver that
just has a single hard coded value so you can just use usleep_range()
directly but it gets awkward once you start being generic and the code
really has no idea what the actual delay it's dealing with is.

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