On Tue, Jun 20, 2017 at 2:32 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > It's possible that the test was invalid. Kai-Heng did not say whether > /sys/.../power/wakeup was set to "enabled" for both the EHCI controller > and the USB root hub beneath it, before the test was started. If > either of them was set to "disabled" then we would not expect a plug or > unplug event to wake up the system. You are right, it's "disabled" on USB root hub. Changed it to "enabled", the test result remains the same. > > In any case, the controller should be set to the lowest power setting > that is consistent with the desired wakeup behavior. If wakeup is set > to "enabled" then the state should be D2 -- if possible. That's the > theory, anyway. If the system supports putting devices only into D3 > during S3 sleep then there's no choice, but if we do have a choice then > we should take it. > > BTW, I just noticed that pci_target_state() uses device_may_wakeup() to > get the desired wakeup behavior. That is correct for system sleep, but > it is wrong for runtime PM. For runtime PM, wakeup should be enabled > whenever the hardware allows it, so the test should be > device_can_wakeup(). > > This means that pci_target_state() should behave differently depending > on whether it is called from pci_prepare_to_sleep() or from > pci_finish_runtime_suspend(). Probably nobody noticed this before > because it usually doesn't make any difference. > > Alan Stern >
