On Wednesday, January 15, 2014 12:12:29 AM Rafael J. Wysocki wrote: > Hi, > > The following experimental series of 3 patches implements a mechanism allowing > subsystems to avoid resuming runtime-suspended devices during system suspend. > > As far as the PM core goes, it introduces a new flag, power.no_suspend, that > will be set by the core for devices which can stay suspended. The idea is that > subsystems should know which devices can stay suspended over system suspend > and to allow them to tell the core about that patch [1/3] changes the calling > convention of the device PM .prepare() callback so that it can return a positive > value on success to be interpreted as "this device has been runtime-suspended > and doesn't need to be resumed" information. If .prepare() returns a positive > number for certain device, the core will set power.no_suspend and will not run > suspend callbacks for device with that flag set going forward (during this > particular system suspend transition). > > However, parents may generally need to be resumed so that the suspend of their > children can be carried out, so the PM core will clear power.no_suspend for > the parents of devices whose power.no_suspend is not set (unless those parents > have power.ignore_children set). > > Patch [2/3] adds a new runtime PM helper function that subsystems can use to > check whether or not a given device is runtime-suspended when .prepare() is being > executed for it. > > Patch [3/3] implements the subsystem part for the ACPI PM domain, because that > is relatively straightforward. If the general approach makes sense, I'll think > about doing the same for PCI. I have a new version of this. The new patch [1/3] goes farther than the previous one, because I realized that all subsystems returning values greater from zero from their .prepare() callbacks will want to skip .resume_noirq() and .resume_early() for the "fast suspended" devices and all of them will likely want to run a pm_request_resume() for those devices in their .resume(). So, if all of them would do that anyway, it's better if the core does that for them. Of course, that simplifies patch [3/3] quite a bit. Patch [2/3] is the same as before. Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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
