On Thursday, June 10, 2010, Alan Stern wrote: > On Thu, 10 Jun 2010, Rafael J. Wysocki wrote: > > > On Tuesday, June 08, 2010, Alan Stern wrote: > > > This patch (as1388) changes the way the PCI core handles runtime PM > > > settings when probing or unbinding drivers. Now the core will make > > > sure the device is enabled for runtime PM, with a usage count >= 1, > > > when a driver is probed. It does the same when calling a driver's > > > remove method. > > > > > > If the driver wants to use runtime PM, all it has to do is call > > > pm_runtime_pu_noidle() near the end of its probe routine (to cancel > > > the core's usage increment) and pm_runtime_get_noresume() near the > > > start of its remove routine (to restore the usage count). It does not > > > need to mess around with setting the runtime state to enabled, > > > disabled, active, or suspended. > > > > > > The patch updates e1000e and r8169, the only PCI drivers that already > > > use the existing runtime PM interface. > > > > > > Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > > > CC: Rafael J. Wysocki <rjw@xxxxxxx> > > > > I like the idea, but I think there's a problem with the patch. > > > > Namely, if there's a driver that doesn't support runtime PM and one of the > > runtime PM helper functions is executed for it, whatever the reason, > > the PCI bus callback run by it will return error code and runtime PM will be > > disabled for the device as a result. > > That can't happen. Because the PCI core increments the usage > count before probing the driver, if the driver doesn't support runtime > PM then the usage count will never fall to 0. Hence the bus callbacks > will never be invoked. Ah, OK then. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
