Decrease long resume time of Intel Bluetooth module

[Paul Menzel <pmenzel@xxxxxxxxxxxxx>]

Dear Linux folks,


The USB Bluetooth device 8087:0a2b is used in quite a lot of portable 
devices. In my case it’s the TUXEDO Book BU1406 [1]. I am trying to 
decrease the overall (suspend and) resume time of the Linux kernel.

```
$ more /proc/version
Linux version 4.10.0+ (helmuth@helmuth-N24-25BU) (gcc version 6.2.0 
20161005 (Ubuntu 6.2.0-5ubuntu12) ) #1 SMP Fri Feb 24 16:56:56 CET 2017
$ lsusb -d 8087:0a2b
Bus 001 Device 002: ID 8087:0a2b Intel Corp.
$ journalctl -k -o cat | grep usb
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb1: Product: xHCI Host Controller
usb usb1: Manufacturer: Linux 4.10.0+ xhci-hcd
usb usb1: SerialNumber: 0000:00:14.0
usb usb2: New USB device found, idVendor=1d6b, idProduct=0003
usb usb2: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb2: Product: xHCI Host Controller
usb usb2: Manufacturer: Linux 4.10.0+ xhci-hcd
usb usb2: SerialNumber: 0000:00:14.0
usb usb3: New USB device found, idVendor=1d6b, idProduct=0002
usb usb3: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb3: Product: xHCI Host Controller
usb usb3: Manufacturer: Linux 4.10.0+ xhci-hcd
usb usb3: SerialNumber: 0000:01:00.0
usb usb4: We don't know the algorithms for LPM for this host, disabling LPM.
usb usb4: New USB device found, idVendor=1d6b, idProduct=0003
usb usb4: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb4: Product: xHCI Host Controller
usb usb4: Manufacturer: Linux 4.10.0+ xhci-hcd
usb usb4: SerialNumber: 0000:01:00.0
usb 1-5: new full-speed USB device number 2 using xhci_hcd
usb 1-5: New USB device found, idVendor=8087, idProduct=0a2b
usb 1-5: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 1-6: new high-speed USB device number 3 using xhci_hcd
usb 1-6: New USB device found, idVendor=5986, idProduct=1112
usb 1-6: New USB device strings: Mfr=3, Product=1, SerialNumber=2
usb 1-6: Product: BisonCam,NB Pro
usb 1-6: Manufacturer: Bison
usb 1-6: SerialNumber: 200901010001
usbcore: registered new interface driver btusb
input: BisonCam,NB Pro as 
/devices/pci0000:00/0000:00:14.0/usb1/1-6/1-6:1.0/input/input21
usbcore: registered new interface driver uvcvideo
```

Suspending and resuming of this devices takes quite a bit of time for 
that device.

From running `analyze_suspend.py` [2] – `scripts/analyze_suspend.py` in 
Linux repository – the following value is measured.

> usb @ 8087:0a2b [1-5] {usb} async_device (Total Suspend: 588.807 ms Total Resume: 561.912 ms)

The overall timings are below.

> Kernel Suspend: 1237.805 ms	Firmware Suspend: 0.000 ms	Firmware Resume: 1.318 ms	Kernel Resume: 869.322 ms

So that device needs over half a second for each of suspend and resume, 
which is the majority of the overall time.

Is there a way to debug and optimize that – besides taking the device 
out – to get resume times on par with other devices like Google 
Chromebooks or Apple MacBooks?


Thanks,

Paul


[1] https://www.tuxedocomputers.com/bu1406
[2] https://01.org/suspendresume/

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