On 11/04/2014 08:10 PM, Alan Stern wrote:
> Now, maybe something went wrong somewhere. Perhaps the kernel thought
> that after the system resume, the root hub was still in runtime
> suspend. If that's true, we need to find out why and fix it.
This is what I have so far (I have no idea what is correct / wrong I
just document what I figured out):
- good case no wakeup active.
- usb_suspend() => choose_wakeup()
"if (udev->state == USB_STATE_SUSPENDED && w !=
udev->do_remote_wakeup)"
w is 0 and do_remote_wakeup is 1. This means pm_runtime_resume() is
invoked.
- device status goes RPM_SUSPENDED => RPM_RESUMING => RPM_ACTIVE
- after we are in usb_suspend_both() and udev->state is 7
(USB_STATE_CONFIGURED), hub_suspend() is beeing invoked.
The status urb is dequeued, RPM of usb1 is still RPM_ACTIVE
- in the bad case (wakeup active)
- usb_suspend => choose_wakeup()
- in the check above we do nothing because w and …do_remote_wakeup
is 1
- usb_suspend_both() does nothing because udev->state is 8
(USB_STATE_SUSPENDED) so we leave. RPM of both devices (hub and
usb1 is RPM_SUSPENDED)
--- now get back out of suspend ---
- usb_resume() is invoked with different RPM status.
- hub_activate() is invoked. The status URB is enqueued again, RPM
remains unchanged.
- aaaaand we are done
- we get a HUB event, khubd is kicked.
- the hub invokes usb_autopm_get_interface() on the interface which is
suspended. The hub device is suspended and has
dev->power.no_callbacks set. Now:
- in the "good" case it sees that the parent (usb1) is still
RPM_ACTIVE so it sets the status of the status of hub to RPM_ACTIVE
and leaves without doing anything.
- in the bad case the ave RPM still set to RPM_SUSPENDED so we call
resume for usb1 again which leads to the second status URB enqueue
So that is the history. I *think* that we shouldn't to hub_suspend() +
hub_resume() without changing the RPM status (the choose_wakeup()
difference). This might also fix the RPM status for usb1 which is in
RPM_SUSPENDED while it should be active (shouldn't it?) since it has
remote_wakeup active.
>
> Alan Stern
>
Sebastian
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