On Sun 2009-02-15 22:23:04, Roland Dreier wrote: > > > (2) put given subset of devices into low power states whenever they > > > are not used, without putting the entire system into a sleep state. > > > For (2), for me the answer is very obvious: > > > The Device Driver needs to make the decision to put the device to sleep. > > There are no ifs and buts about this. > > For PC-like systems this is probably all that needs to be said. However > for highly integrated SoC systems (as Android is obviously targeting) > there is another level of complexity due to the interdependency among > various devices... eg things like if I know the SD controller and the > wifi chip are both asleep then I can put my SDIO controller to sleep; > and if the SDIO controller and the NAND controller are both asleep then > I can stop clock X and save more power; etc etc. > > This is what the PowerOp/DPM work was all about. Unfortunately that > doesn't seem to have made much progress upstream. But there's no doubt > in my mind that we need some framework beyond individual drivers that > manages the system's power as a whole. And the current device tree is > probably not sufficient -- eg the bus hierarchy of a device may not > match up with the clock tree at all. Well, that's why clock framework exists. But none of this is visible to userland. -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
