On Tue, 4 May 2010, Matthew Garrett wrote: > On Mon, May 03, 2010 at 04:37:22PM -0700, Kevin Hilman wrote: > > > Please forgive the ignorance of ACPI (in embedded, we thankfully live > > in magical world without ACPI) but doesn't that already happen with > > CPUidle and C-states? I think of CPUidle as basically runtime PM for > > the CPU. IOW, runtime PM manages the devices, CPUidle manages the CPU > > (via C-states), resulting in dynaimc PM for the entire system. What > > am I missing? > > ACPI doesn't provide any functionality for cutting power to most devices > other than shifting into full system suspend. The number of wakeup > events available to us on a given machine is usually small and the > wakeup latency large, so it's not terribly practical to do this > transparently on most hardware. Another thing that Kevin is missing: There is more to the system than the devices and the CPU. For example: RAM, an embedded controller (on modern desktop/laptop systems), a power supply, and so on. Dynamic PM for the CPU and the devices won't power-down these things, but system PM will. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
