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

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Date:   Mon, 13 Aug 2018 16:15:02 +0530
From:   Anshuman Gupta <anshuman.gupta@...el.com>
To:     oneukum@...e.com, linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, anshuman.gupta@...el.com
Subject: Re: [Query] USB device autosuspend and its runtime usage count.

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@...el-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/runtime_enabled
> > enabled
> > root@...el-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/control
> > auto
> > root@...el-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/autosuspend_delay_ms
> > 2000
> > root@...el-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/runtime_status
> > active
> > root@...el-Kabylake-Client-platform:# cat /sys/bus/usb/devices/1-5/power/runtime_usage
> > 1
> > root@...el-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@...el-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@...el-Kabylake-Client-platform:# lsusb 
Bus 001 Device 003: ID 04d9:1702 Holtek Semiconductor, Inc. Keyboard LKS02

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