On Tuesday 09 June 2009, Magnus Damm wrote: > On Sat, Jun 6, 2009 at 5:42 AM, Rafael J. Wysocki<rjw@xxxxxxx> wrote: > > On Friday 05 June 2009, Magnus Damm wrote: > >> On Wed, Jun 3, 2009 at 6:05 PM, Rafael J. Wysocki<rjw@xxxxxxx> wrote: > >> > On Friday 29 May 2009, Magnus Damm wrote: > >> >> 2009/5/29 Rafael J. Wysocki <rjw@xxxxxxx>: > >> >> > On Wednesday 27 May 2009, Magnus Damm wrote: > >> >> >> From: Magnus Damm <damm@xxxxxxxxxx> > >> >> >> > >> >> >> Add platform_device_idle() and platform_device_wakeup() > >> >> >> and allow architectures to implement their own versions > >> >> >> of these if CONFIG_HAVE_PLATFORM_IDLE_WAKEUP is set. > >> >> >> > >> >> >> Signed-off-by: Magnus Damm <damm@xxxxxxxxxx> > >> >> >> --- > > >> The wakeup()/idle() code in this patch is one way to solve it on a > >> platform device level. Another more generic way would be to add > >> ->enable() and ->disable() callbacks to struct bus_type and introduce > >> device_enable() and device_disable() that takes struct device and > >> invokes the bus callbacks if set. > > > > So, you need a generic mechanism that drivers can use to notify the bus type > > code that a device is idle and therefore it should schedule an autosuspend > > request for the device. Also, you want a mechanism by which drivers can notify > > the platform code that there is a need to wake-up an autosuspended device. > > Is that correct? > > Yes, you are 100% correct that I want drivers to have some way to > notify the bus type that a certain device is idle or needs to be woken > up. > > Exactly what should happen when the device is marked as idle is a > different question. I guess this is bus specific. Connecting the idle > notification directly to autosuspend is not a very good idea IMO since > the power management comes with latency restrictions. > > If we zoom out a bit then I think that we should have something > similar to cpuidle but for devices. Maybe the driver should give a > list of suspend modes, their latencies and power savings. This per > driver (or per device) latency information is important, but even more > important IMO is latency information for the bus itself. > > So for our on-chip SuperH SoC platform devices I'd like to keep track > of which devices that are idle, and if all devices within one power > domain are idle then i'd like to execute autosuspend() for those and > after that power off the bus/domain. But only if this doesn't break > any latency requirements. OK, I think we can add ->idle() and ->wakeup() callbacks to struct bus_type for this purpose. BTW, I'm waiting for a new version of your patch adding the arch data to struct platform_device with a better changelog. Best, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
