On Monday 03 May 2010, Mark Brown wrote: > On Mon, May 03, 2010 at 09:40:26AM -0700, Kevin Hilman wrote: > > > At least from the kernel perspective, both suspend blockers and > > runtime PM have the same goal. Given that, which framework should the > > driver writer target? Both? Seems like duplicate effort. Using > > suspend blockers assumes the system is in opportunitstic suspend mode > > and (at least in the keypad example given) assumes a suspend-blocker > > aware userspace (Android.) Without both, targeted power savings will > > not be acheived. > > The other concern here is that for many mobile systems the actual > semantic intended by "suspend" as it's currently used is more runtime PM > like than full suspend - the classic example of this is that when > suspending while on a call in a phone you don't want to suspend the > modem or audio CODEC, you want to leave them running. If you use a full > system suspend then the drivers for affected components have to play > guessing games (or add currently non-standard knobs for apps to twiddle) > to decide if the system intends them to actually implement the suspend > or not but with runtime PM it all falls out very naturally without any > effort on the part of the driver. > > > To me, runtime PM is a generic and flexible approach that can be used > > with any userspace. Driver writers should not have to care whether > > the system is in "opportunistic" mode or about whether userspace is > > suspend blocker capable. They should only have to think about when > > the device is (or should be) idle. > > I fully agree with this. We do need to ensure that a runtime PM based > system can suspend the CPU core and RAM as well as system suspend can > but that seems doable. I _think_ it would be hard at least. On ACPI-based systems it's not doable at all AFAICS. However, the real question is whether or not the opportunistic suspend feature is worth adding to the kernel as such and I think it is. To me, it doesn't duplicate the runtime PM framework which is aimed at the power management of individual devices rather than the system as a whole. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
