On Friday, August 06, 2010, Alan Stern wrote: > On Thu, 5 Aug 2010, Arve Hjønnevåg wrote: ... > But what sorts of things qualify as wakeup events? Right now, the code > handles only events coming by way of the PME# signal (or its platform > equivalent). But that signal usually gets activated only when a PCI > device is in a low-power mode; if the device is at full power then it > simply generates an IRQ. It's the same event, but reported to the > kernel in a different way. So consider... > > Case 1: The system is suspending and the PCI device has already been > placed in D3hot when an event occurs. PME# is activated, > the wakeup event is reported, the suspend is aborted, and the > system won't try to suspend again for at least 100 ms. Good. > > Case 2: The system is running normally and the PCI device is at full > power when an event occurs. PME# isn't activated and > pm_wakeup_event doesn't get called. Then when the system > tries to suspend 25 ms later, there's nothing to prevent it > even though the event is still being processed. Bad. > > In case 2 the race has not been resolved. It seems to me that the > only proper solution is to call pm_wakeup_event for _every_ PCI > interrupt. This may be too much to add to a hot path, but what's the > alternative? Arguably not every PCI interrupt should be regarded as a wakeup event, so I think we can simply say in the cases when that's necessary the driver should be responsible for using pm_wakeup_event() or pm_stay_awake() / pm_relax() as appropriate. My patch only added it to the bus-level code which covered the PME-based wakeup events that _cannot_ be handled by device drivers. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
