On Tuesday 04 May 2010, Rafael J. Wysocki wrote: > On Tuesday 04 May 2010, Kevin Hilman wrote: > > Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx> writes: > > > > > On Mon, May 03, 2010 at 05:43:34PM -0700, Brian Swetland wrote: > > >> On Mon, May 3, 2010 at 5:09 PM, Arve Hjønnevåg <arve@xxxxxxxxxxx> wrote: > > >> > On Mon, May 3, 2010 at 4:37 PM, Kevin Hilman > > > > > >> >> This last point is especially troubling. I don't find it a comforting > > >> >> path to go down if the drivers have to start caring about which PM > > >> >> policy is currently in use. > > > > > >> I'll echo Arve here -- all drivers should seek to be in the lowest > > >> power state possible at all times. We've never suggested that > > >> suspend_block is a substitute for that. > > > > > > Looking at this from a subsystem/driver author point of view the problem > > > I'm faced with is that as a result of using system suspend much more > > > aggressively the subsystem and driver layers are getting conflicting > > > instructions about what the lowest power state possible is. > > > > Exactly. > > > > With runtime PM, there is flexibility in choosing the lowest power > > state at the device/subsystem level, based on activity, timeouts, > > bitrate, dependencies, latency/throughput constraints, etc. > > > > With opportunistic suspend, all of this flexibility is gone, and the > > device/subsystem is told to go into the lowest power, highest latency > > state, period. > > Guys, please. > > The opportunistic suspend feature is _not_ to replace runtime PM by any means! > > However, there are situations in which runtime PM is clearly insufficient. > The idea behind runtime PM is that subsystems and device drivers will know > when to put devices into low power states and save energy this way. Still, > even if all subsystems do that 100% efficiently, there may be more savings > possible by putting the entire system into a sleep state (like on ACPI-based > PCs) and we can reach there by runtime PM alone. s/can/can't/; s/reach/go/ Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
