On Thursday, June 23, 2011, Kevin Hilman wrote: > "Rafael J. Wysocki" <rjw@xxxxxxx> writes: > > > On Wednesday, June 22, 2011, Kevin Hilman wrote: > >> "Rafael J. Wysocki" <rjw@xxxxxxx> writes: > >> > >> > From: Rafael J. Wysocki <rjw@xxxxxxx> > >> > > >> > Make generic PM domains support system-wide power transitions > >> > (system suspend and hibernation). Add suspend, resume, freeze, thaw, > >> > poweroff and restore callbacks to be associated with struct > >> > generic_pm_domain objects and make pm_genpd_init() use them as > >> > appropriate. > >> > > >> > The new callbacks do nothing for devices belonging to power domains > >> > that were powered down at run time (before the transition). > >> > >> Great, this is the approach I prefer too, but... > >> > >> Now I'm confused. Leaving runtime suspended devices alone is what I was > >> doing in my subsystem but was told not to. According to > >> > >> http://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg50690.html > >> > >> "it's generally agreed that _all_ devices should return to full > >> power during system resume -- even if they were runtime suspended > >> before the system sleep." > > > > Well, let's say this part of the documentation is slightly outdated. > > > > It basically refers to the model in which system suspend is a separate global > > hardware or firmware operation, so the state of devices may be changed by the > > BIOS or whatever takes over control in the meantime. In that case the kernel > > has to ensure that the states of devices are consistent with what it thinks > > about them and the simplest way to achieve that is to put the devices to > > full power during resume (and back to low power if that's desirable). > > > > However, in the case of the systems this patchset is intended for system > > suspend is achieved by putting various hardware components into low-power > > states directly in a coordinated way and the system sleep state effectively > > follows from the low-power states the hardware components end up in. The > > system is woken up from this state by an interrupt or another mechanism under > > the kernel's control. As a result, the kernel never gives control away, so > > the state of devices after the resume is precisely known to it. > > In consequence, it need not ensure that the state of devices is consistent with > > its view, because it knows that this is the case. :-) > > > > So the documentation should be updated to say what hardware model it is > > referring to. > > Great! Thanks for the clarification. No problem, I guess I should update the documentation eventually. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
