On 02/23/2014 12:51 AM, Alan Stern wrote:
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()).
Thanks Dan and Alan for the input, I did the following changes:
- Take and release the reference in xhci_pci_probe to avoid releasing
the reference for a moment just before usb3 roothub registration.
- Make sure we release the reference in error cases
- Still use _put_noidle as driver_probe_device calls pm_request_idle
-Mathias
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