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

Alan Stern
2018-08-13T14:05:01Z

On Mon, 13 Aug 2018, Anshuman Gupta wrote:

> 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

What matters is not the power/* settings for the interfaces themselves,
but rather the power/* settings for the interfaces' children.

Alan Stern