On Tuesday, July 10, 2012, Alan Stern wrote: > On Tue, 10 Jul 2012, Rafael J. Wysocki wrote: > > > > > Anyway, you can't force the device into a low-power state using > > > > runtime PM after a failing probe, at least in general. > > > > > > Well, using PM domains, that's exactly what can happen if the driver > > > doesn't call pm_runtime_disable() because the _put_sync() in the driver > > > core will trigger the PM domain callbacks. > > > > OK, so if you have PM domains, then the case is equivalent to having a bus > > type with its own runtime PM callbacks. In that case, if .probe() fails, > > it obviously doesn't mean that the device shouldn't be power managed, > > so the driver shouldn't call pm_runtime_disable(). > > > > Generally, if runtime PM was enabled for a device before .probe() has been > > called, the driver shouldn't disable it in .probe() whatever the reason, > > because it may not have enough information for deciding whether or not > > runtime PM should be disabled. > > So if the PM domain code called pm_runtime_enable() then the domain > code should be responsible for calling pm_runtime_disable() too, > presumably after putting the device back into a low-power state. I'm > not sure when that would occur, however. Immediately after registering > the device, if no driver is bound? > > In the case where the probe routine called pm_runtime_enable(), you're > stuck. The probe routine _has_ to call pm_runtime_disable() when a > failure occurs, to keep the disable count balanced. Yes, I has just been thinking about that. If .probe() enabled runtime PM and called pm_runtime_get_sync() (or _resume), it can't clean up properly in case of an error, because its pm_runtime_put_sync() (or _suspend) won't be effective and you're right that it has to call pm_runtime_disable(). So, we don't handle this particular case correctly. I'm not sure what the solution should be, though. We could remove the runtime PM operations around really_probe(), but then there may be drivers assuming that the core will call pm_runtime_put_sync() after .probe() has returned. Thanks, Rafael
