Hi, On Fri, Jan 31, 2014 at 04:34:27PM -0500, Alan Stern wrote: > On Fri, 31 Jan 2014, Felipe Balbi wrote: > > > Still TODO a commit log. Not for merging!!!!! > > > > NYET-Signed-off-by: Felipe Balbi <balbi@xxxxxx> > > --- > > > > This patch is an idea I've had recently in order to combine several different > > PM implementations into the platform-bus. > > > > This patch is bare minimum for platforms which need to handle functional and > > interface clocks but the whole thing is made optional. > > > > Note that this patch makes sure that by the time a platform_driver's probe is > > called, we already have clocks enabled and pm_runtime_set_active() has been > > called, thus making sure that a device driver's pm_runtime_get_sync() will > > solely increase the pm usage counter. > > > > I have *NOT* tested this anywhere *YET*, but I suppose it shouldn't cause any > > issues since the clock API has ref counting too. > > > > Would really like to get some review from several folks involved with ARM SoC > > PM so that's the reason for the wide audience. If I have missed anybody, please > > add them to Cc. > > > > As mentioned above, this is *NOT* meant for merging, but serves as a starting > > point for discussing some convergence of several PM domain implementations on > > different arch/arm/mach-* directories. > > You might want to copy the runtime-PM approach used by the PCI > subsystem. It works like this: > > The core invokes a driver's probe routine with runtime PM > enabled, the device in the ACTIVE state, and the usage counter > incremented by 1. > > If the driver wants to support runtime PM, the probe routine > can call pm_runtime_put_noidle. > > The core does pm_runtime_get_sync before invoking the driver's > remove routine. At this point a runtime-PM-aware driver whould > call pm_runtime_get_noresume, to balance the _put during probe. > > After invoking the remove routine, the core does a put_noidle > (to balance the get_sync) and a final put_sync (to balance the > increment before probe and to leave the device at low power.) > > A nice consequence is that everything is transparent for drivers that > don't support runtime PM. The usage counter remains > 0 the entire > time the driver is bound. > > Conversely, drivers that do support runtime PM merely have to add one > call during probe and one during remove. > > There is one tricky aspect to all this. The driver core sets the > dev->driver field before calling the subsystem core's probe routine. > As a result, the subsystem has to be very careful about performing > runtime PM before invoking the driver's probe routine. Otherwise you > will end up calling the driver's runtime_resume callback before the > driver's probe! (And of course, the same problem exists in reverse > during remove.) I can, certainly, do that and that would, most likely, simplify a whole bunch of drivers. But that change, I suppose, would be a whole lot more invasive. I'll spend some time studying PCI pm_runtime support, thanks for the tip. cheers -- balbi
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