On Saturday 29 May 2010, Arve Hjønnevåg wrote: > 2010/5/29 Rafael J. Wysocki <rjw@xxxxxxx>: > > On Saturday 29 May 2010, Arve Hjønnevåg wrote: > >> 2010/5/28 Rafael J. Wysocki <rjw@xxxxxxx>: > >> > On Friday 28 May 2010, Arve Hjønnevåg wrote: > >> >> On Fri, May 28, 2010 at 1:44 AM, Florian Mickler <florian@xxxxxxxxxxx> wrote: > >> >> > On Thu, 27 May 2010 20:05:39 +0200 (CEST) > >> >> > Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > >> > ... > >> >> > To integrate this with the current way of doing things, i gathered it > >> >> > needs to be implemented as an idle-state that does the suspend()-call? > >> >> > > >> >> > >> >> I think it is better no not confuse this with idle. Since initiating > >> >> suspend will cause the system to become not-idle, I don't think is is > >> >> beneficial to initiate suspend from idle. > >> > > >> > It is, if the following two conditions hold simultaneously: > >> > > >> > (a) Doing full system suspend is ultimately going to bring you more energy > >> > savings than the (presumably lowest) idle state you're currently in. > >> > > >> > (b) You anticipate that the system will stay idle for a considerably long time > >> > such that it's worth suspending. > >> > > >> > >> I still don't think this matters. If you are waiting for in interrupt > >> that cannot wake you up from suspend, then idle is not an indicator > >> that it is safe to enter suspend. I also don't think you can avoid any > >> user-space suspend blockers by delaying suspend until the system goes > >> idle since any page fault could cause it to go idle. Therefore I don't > >> see a benefit in delaying suspend until idle when the last suspend > >> blocker is released (it would only mask possible race conditions). > > > > I wasn't referring to suspend blockers, but to the idea of initiating full > > system suspend from idle, which I still think makes sense. If you are > > waiting for an interrupt that cannot wake you from suspend, then > > _obviously_ suspend should not be started. However, if you're not waiting for > > such an interrupt and the (a) and (b) above hold, it makes sense to start > > suspend from idle. > > > > What about timers? When you suspend timers stop (otherwise it is just > a deep-idle mode), and this could cause problems. Some drivers rely on > timers if the hardware does not have a completion interrupt. It is not > uncommon to see send command x then wait 200ms in a some hardware > specs. QoS should be used in such cases. Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
