On 11/06/2014 08:16 PM, Alan Stern wrote:
>> --- 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
>
> Ah. In usb_resume(), what happened after usb_resume_both() returned?
> The code says this:
>
> status = usb_resume_both(udev, msg);
> if (status == 0) {
> pm_runtime_disable(dev);
> pm_runtime_set_active(dev);
> pm_runtime_enable(dev);
> unbind_marked_interfaces(udev);
> }
>
> So if usb_resume_both() returns 0, the runtime PM status is supposed to
> get changed to RPM_ACTIVE by the pm_runtime_set_active() call.
so it returns 0 but pm_runtime_set_active() return with -EBUSY:
__pm_runtime_set_status() {
…
if (parent) {
if (… && parent->power.runtime_status != RPM_ACTIVE) {
error = -EBUSY;
…
if (error)
goto out;
…
The parent is musb-hdrc.1.auto. The sort order of resume is:
musb-dsps 47401c00.usb: bus resume
=> dsps_resume() (glue layer)
musb-hdrc musb-hdrc.1.auto: bus resume
=> musb_resume(2328)
and after musb_resume() completes I see usb_resume() being invoked (and
the first hub resume).
Later, once khubd kicks in, I see musb_runtime_resume() probably via
usb_autopm_get_interface(hub).
That means the musb-hcd is not RPM_ACTIVE after resume and this is what
USB expects.
If I put pm_runtime_get_sync() + put in musb_resume() then the problem
is gone. I don't see ehci-hcd doing this in resume, in fact I don't see
ehci doing pm_runtime_* at all. So for ehci the device is probably
always RPM_ACTIVE.
And musb does it only in probe and nowhere else. I would expect it in
the ISR as well but it is what it is.
On the the other hand: musb_resume() invokes usb_hcd_resume_root_hub()
what probably brings usb_resume() for the hub into the game. Shouldn't
it pm_get_sync() the HCD? And still, if the HCD has a short suspend
delay it might go into suspend before the khubd is invoked (but then it
probably kills the status URB).
> Alan Stern
Sebastian
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