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. Comments welcome! Thanks, Rafael -- 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
