On Sat, 22 Feb 2014, Dan Williams wrote: > On Fri, Feb 21, 2014 at 1:17 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 21 Feb 2014, Dan Williams wrote: > > > >> > Round 2: add usb 3 hcd > >> > > >> > usb_add_hcd() // secondary usb3 hcd > >> > hcd->self.root_hub = usb_alloc_dev() > >> > hcd->driver->reset(hcd) -> xhci_gen_setup() > >> > if(primary_hcd) // false > >> > .. > >> > else > >> > pm_runtime_put_noidle(hcd->self.controller) // -1 usage, * > >> > register_root_hub(hcd) -> usb_new_device(usb_dev) > >> > pm_runtime_set_active(&udev->dev); > >> > pm_runtime_get_noresume(&udev->dev); > >> > pm_runtime_use_autosuspend(&udev->dev); > >> > pm_runtime_enable(&udev->dev); > >> > ... > >> > pm_runtime_put_sync_autosuspend(&udev->dev); // ok to trigger would > >> > trigger xhci_suspend if all usages were 0. > >> > > >> > *) unnecessary to trigger any suspend as we're just about to register the > >> > usb3 roothub. but we need to decrement the usage counter. > >> > >> Right, but I assume you'd want to hold the reference until after the > >> hub is registered, otherwise there's still a chance we suspend right > >> before register. So I'm saying hold the reference until the > >> registration process takes its own. > > > > To be really safe about it, you should call pm_runtime_get_noresume at > > the start of xhci_pci_probe, and pm_runtime_put_noidle at the end > > Why _put_noidle? The fact that we suspend between registrations means > the controller is getting suspend requests that we will block with > _get_noresume. However, once probe is done our final put might be the > only one to trigger the deferred suspension. I.e. just worried about > the case where the controller's usage count is 0, but it remains > active indefinitely. Either _put_sync or _put_noidle would be okay. The reason is because the device core always calls pm_request_idle after probing a driver (see driver_probe_device()). > > (as well as in the error return pathways). > > Sounds like an example case for a new devm_pm_runtime_get() api. Maybe... Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
