On Sat, May 15, 2010 at 2:25 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Fri, 14 May 2010, Arve Hjønnevåg wrote: > >> > I'd like to explore this avenue a little farther. In particular, what >> > is the issue involving loss of wakeup events? Can you describe this in >> > more detail? >> > >> >> On the desktop systems I have used I only wake the up the system by >> pressing a button/key or with an rtc alarm. Losing a button or key >> wakeup event is not usually a problem on a desktop since the user will >> press it again. Losing an alarm however could be a problem and this >> can be avoided by using opportunistic suspend and suspend blockers. > > How can runtime PM combined with CPUidle cause an alarm to be lost? > It doesn't. My desktop systems only gets to a low power state (<3W) from suspend. >> > Why would you want to use system suspend if runtime PM can do >> > everything you need? >> > >> Because it stops threads that wakeup every second to check if they >> have work to do (this includes standard kernel threads), and it >> prevents bad apps that never go idle from completely destroying our >> battery life. > > Ah, the ill-behaved apps problem. I think everybody agrees that they > are hard to deal with. > > The kernel-threads problem might better be addressed by fixing those > threads than by adding a new API. > >> > Sure, I can see that an ACPI-based system needs something more. But >> > that's not the real issue here. >> > >> >> The system we started with entered a much lower power state from >> suspend than idle so we needed wakelocks to get more than 24 hours >> battery life. We kept wakelocks when we moved to the msm platform >> since it reduces our power consumption. > > Is it generally true among embedded systems nowadays that idle is > capable of reaching essentially the same power states as suspend? Embedded system in general, no, but all the recent SOCs I've seen that target phones do. -- Arve Hjønnevåg _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
