On Thursday, May 03, 2012, Mark Brown wrote: > On Thu, May 03, 2012 at 02:59:25PM +0200, Rafael J. Wysocki wrote: > > On Thursday, May 03, 2012, Linus Walleij wrote: > > > > If *all* runtime_resume() hooks for *all* devices in the same power > > > domain are called at this time on the way up/down we get a major > > > overhead as our primary power domain is pretty big. > > > FWIW, in the generic PM domains framework used on the sh7372 platform we have > > a need_restore flag whose meaning is whether or not to call .runtime_suspend() > > (or its domain-specific counterpart) when the domain is about to be powered > > off and .runtime_resume() when the device is resumed by the runtime PM > > framework. Those two callbacks are meant to save and restore the device's > > state, respectively, and there are two more domain-specific callbacks, > > .stop() and .start() that (in the case of sh7372) manipiulate the devices' > > clocks. > > > So, if pm_runtime_suspend() is called for a device, we first check if it's OK > > to call .stop() for it (according to PM QoS constraints), but we don't call > > .runtime_suspend() for it yet at this point. Next, we check if it's OK to > > power off the domain containing the device (taking PM QoS constraints and > > subdomains into consideration) and if we decide to do that, we call > > .runtime_suspend() for the devices in the domain, but only those whose > > need_restore flags are unset. Then, if pm_runtime_resume() is called for > > one of the devices, we check its need_restore flag and call .runtime_resume() > > for the device if the flag set and .start() is called subsequently. > > This seems like a really useful idiom in general - might it be worth > supporting as a standard framework feature? The generic PM domains framework does this, it's not platform-specific (if I understood your question correctly). Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
