Re: [PATCH 1/2] PM / runtime: Allow drivers to override runtime PM behaviour on sleep

[Thierry Reding <thierry.reding@gmail.com>]

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On Thu, Nov 28, 2019 at 05:14:51PM +0100, Rafael J. Wysocki wrote:
> On Thu, Nov 28, 2019 at 5:03 PM Thierry Reding <thierry.reding@gmail.com> wrote:
> >
> > From: Thierry Reding <treding@nvidia.com>
> >
> > Currently the driver PM core will automatically acquire a runtime PM
> > reference for devices before system sleep is entered. This is needed
> > to avoid potential issues related to devices' parents getting put to
> > runtime suspend at the wrong time and causing problems with their
> > children.
> 
> Not only for that.
> 
> > In some cases drivers are carefully written to avoid such issues and
> > the default behaviour can be changed to allow runtime PM to operate
> > regularly during system sleep.
> 
> But this change breaks quite a few assumptions in the core too, so no,
> it can't be made.

Anything in particular that I can look at? I'm not seeing any issues
when I test this, which could of course mean that I'm just getting
lucky.

One thing that irritated me is that I think this used to work. I do
recall testing suspend/resume a few years ago and devices would get
properly runtime suspended/resumed. I did some digging but couldn't
find anything that would have had an impact on this.

Given that this is completely opt-in feature, why are you categorically
NAK'ing this?

Is there some other alternative that I can look into?

Thierry

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