Re: [Query] USB device autosuspend and its runtime usage count.

Anshuman Gupta
2018-08-13T10:47:09Z

On Mon, Aug 13, 2018 at 01:19:26PM +0530, Oliver Neukum wrote:
> On Mo, 2018-08-13 at 12:15 +0530, Anshuman Gupta wrote:
> > Hi ,
> > I need to test a functionality with USB autosuspend with latest kernel
> > Linux 4.18-rc8. I am trying to autosuspend a USB key board, i enabled
> > its autosuspend by doing echo "auto" to its "control" attributes.
> > I am expecting USB keyboard to go to autosuspend after autosuspend_delay_ms.
> > But USB key board is not going to autosuspend because its runtime usage
> > count is not equal to zero.
> >
> > Below are the log snippets:
> >
> > root@intel-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/runtime_enabled
> > enabled
> > root@intel-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/control
> > auto
> > root@intel-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/autosuspend_delay_ms
> > 2000
> > root@intel-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/runtime_status
> > active
> > root@intel-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/runtime_usage
> > 1
> > root@intel-Kabylake-Client-platform:# sleep 60; cat /sys/bus/usb/devices/1-5/power/runtime_usage
> > 1
> >
> > My USB keyboard runtime usage reference count is not decreasing to zero.
> > Here am i missing something regarding runtime usage count or is it some issue with
> > my kernel or OS?
>
> Very hard to say without further information. Is the HID device the
> only interface of the whole device?
yes, HID device is only the interface for given device, below here lsusb -t log for usb dev 1-5.

root@intel-Kabylake-Client-platform:# lsusb -t
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/12p, 480M
|__ Port 5: Dev 3, If 1, Class=Human Interface Device, Driver=usbhid, 1.5M
|__ Port 5: Dev 3, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M

> Does the device support remote wakeup?
yes, from lsusb logs it seems, it is supporting remote wakeup.

root@intel-Kabylake-Client-platform:# lsusb
Bus 001 Device 003: ID 04d9:1702 Holtek Semiconductor, Inc. Keyboard LKS02

root@intel-Kabylake-Client-platform:# lsusb -v -d 04d9:1702 | grep Remote
Remote Wakeup

> Is an LED on?
Num lock led was on, but switching it off also does not help.
>
> Usbhid does support autosuspend, but its criteria must be met.
> And all interface drivers must call the device idle.
All of its interfaces are in runtime suspend

root@intel-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5\:1.0/power/runtime_status
suspended
root@intel-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5\:1.1/power/runtime_status
suspended
root@intel-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/runtime_active_kids
0

> Or you have discovered a kernel bug.
>
> Regards
> Oliver
>

--
Thanks,
Anshuman