Forcing devices into idle

[Rafael J. Wysocki]

On Thu, Jul 3, 2025 at 12:33 PM Oliver Neukum <oneukum at suse.com> wrote:
>
> On 03.07.25 12:08, Thierry Reding wrote:
>
> > Any thoughts on how to solve this? Is the pm_runtime_{put,get}_sync()
> > method acceptable? If not, are there other alternatives to achieve the
> > same thing that I'm not aware of? Would it be useful to add a new set of
> > APIs to force devices into an idle state (which could be semantically
> > different from runtime suspend)? Or is this all too specific for any
> > kind of generic API?
>
> Basically what you need is what happens when the system prepares to
> do a snapshot for S4. However, if you just perform FREEZE and then THAW,
> devices will assume that user space has been frozen. You need a way
> to substitute for that assumption.

Well, you just need to freeze user space beforehand.

> Runtime power management is unlikely to be a fruitful approach to your
> needs.

Agreed.