On Sat, 4 Jul 2009, Rafael J. Wysocki wrote: > > As for whether or not we should actually call cancel_work... Which is > > more expensive: Calling cancel_work when no work is pending, or letting > > the work item run when it doesn't have anything to do? Probably the > > latter. > > Agreed, but that doesn't affect functionality. We can get the desired > functionality without the cancel_work() patch and then optimize things along > with that patch. This way it'll be easier to demontrate the benefit of it. Good idea. > That almost entirely depends on the bus type. For PCI and probably PNP as well > there's a notion of ACPI low power states and there are AML methods to put the > devices into these states. Unfortunately, the ACPI low power state to put the > device into depends on the target sleep state of the system, so these devices > will probably have to be put into D0 before system suspend anyway. > > I think that the bus type can handle this as long as it knows the state the > device is in before system suspend. So, the only thing the core should do is > to block the execution of run-time PM framework functions during system > sleep and resume. The state it leaves the device in shouldn't matter. > > So, I think we can simply freeze the workqueue, set the 'disabled' bit for each > device and wait for all run-time PM operations on it in progress to complete. > > In the 'disabled' state the bus type or driver can modify the run-time PM > status to whatever they like anyway. Perhaps we can provide a helper to > change 'request type' to RPM_REQ_NONE. The only modification that really makes sense is like you said, going back to full power in preparation for the platform suspend operation. Therefore perhaps we should allow pm_runtime_resume to work even when rpm_disabled is set. And if we're going to cancel pending suspend and idle requests, then rpm_request would normally be RPM_REQ_NONE anyway. Which leaves only the question of what to do when a resume request is pending... > So, I guess we have the majority of things clarified and perhaps its time to > write a patch for further discussion. :-) Go ahead! Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
