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

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Date:   Mon, 13 Aug 2018 12:15:58 +0530
From:   Anshuman Gupta <anshuman.gupta@...el.com>
To:     linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, anshuman.gupta@...el.com
Subject: [Query] USB device autosuspend and its runtime usage count.

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?

Thanks,
Anshuman Gupta.