On 17 November 2017 at 15:31, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > On Fri, Nov 17, 2017 at 2:49 PM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: >> [...] >> >>>> >>>>>> Second, have you considered setting the default value of >>>>>> dev->power.may_skip_resume to true? >>>>> >>>>> Yes. >>>>> >>>>>> That would means the subsystem >>>>>> instead need to implement an opt-out method. I am thinking that it may >>>>>> not be an issue, since we anyway at this point, don't have drivers >>>>>> using the LEAVE_SUSPENDED flag. >>>>> >>>>> Opt-out doesn't work because of the need to invoke the "noirq" callbacks. >>>> >>>> I am not sure I follow that. >>>> >>>> Whatever needs to be fixed on the subsystem level, that could be done >>>> before the driver starts using the LEAVE_SUSPENDED flag. No? >>> >>> That requires a bit of explanation, sorry for being overly concise. >>> >>> The core calls ->resume_noirq from the middle layer regardless of >>> whether or not the device will be left suspended, so the >>> ->resume_noirq cannot do arbitrary things to it. Setting >>> may_skip_resume by the middle layer tells the core that the middle >>> layer is ready for that and is going to cooperate. If may_skip_resume >>> had been set by default, that piece of information would have been >>> missing. >> >> Huh, I still don't get that. Sorry. >> >> If the "may_skip_resume" is default set to true by the PM core, >> wouldn't that just mean that the middle-layer needs to implement an >> opt-out method, rather than opt-in. In principle to opt-out the >> middle-layer needs to set may_skip_resume to false in suspend_noirq >> phase, no? > > Yes, but if the middle-layer doesn't clear it, that may mean two > things. First, the middle layer is ready and so on. Good. Second, > the middle layer is not aware of the whole thing. Not good. The core > cannot tell. > > In the opt-in case, however, all is clear. :-) Okay. > >> Then we only need to make sure drivers don't starts use >> LEAVE_SUSPENDED, before we make sure the middle layers is adopted. But >> that should not be a problem. >> >> The benefit would be that those middle layers that can cope with >> LEAVE_SUSPENDED as of today don't need to change. > > I'm not sure if that's the case. > > The middle layer has to evaluate dev_pm_may_skip_resume() in > ->resume_noirq() to check if the device can be left in suspend, as it > cannot determine that in ->suspend_noirq() yet. Right. Okay, let's stick with the chosen method. Kind regards Uffe
