Date:	Wed, 25 Nov 2015 10:42:28 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Daniel J Blueman <daniel@...ra.org>,
	Mathias Nyman <mathias.nyman@...el.com>
cc:	USB list <linux-usb@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [4.3] kworker busy in pm_runtime_work

On Wed, 25 Nov 2015, Daniel J Blueman wrote:

> On 23 November 2015 at 23:52, Alan Stern <stern@...land.harvard.edu> wrote:
> > On Sun, 22 Nov 2015, Daniel J Blueman wrote:
> >
> >> On 16 November 2015 at 23:22, Alan Stern <stern@...land.harvard.edu> wrote:
> >> > On Mon, 16 Nov 2015, Daniel J Blueman wrote:
> >> >
> >> >> Tuning USB suspend [1] in 4.3 on a Dell XPS 15 9553 (Skylake), I see a
> >> >> kworker thread spinning in rpm_suspend [2].
> >> >>
> >> >> What is the most useful debug to get here beyond the immediate [3]?
> >> >
> >> > You can try doing:
> >> >
> >> >         echo 'module usbcore =p' >/sys/kernel/debug/dynamic_debug/control
> >>
> >> kworker and ksoftirqd spinning occurs when I echo 'auto' to all the
> >> USB control entries. Using Alan's excellent tip, we see this being
> >> logged repeatedly at a high rate:
> >> [  353.245180] usb usb1-port4: status 0107 change 0000
> >> [  353.245194] usb usb1-port12: status 0507 change 0000
> >> [  353.245202] hub 1-0:1.0: state 7 ports 16 chg 0000 evt 0000
> >> [  353.245203] hub 1-0:1.0: hub_suspend
> >> [  353.245205] usb usb1: bus auto-suspend, wakeup 1
> >> [  353.245206] usb usb1: bus suspend fail, err -16
> >> [  353.245207] hub 1-0:1.0: hub_resume
> >> ...
> >>
> >> So, EBUSY. Both the webcam is not open, and the bluetooth interface
> >> [1] is rfkill'd; the situation occurs even if I unload all related
> >> modules.
> >>
> >> What further debug would be useful?
> >>
> >> Thanks!
> >>   Daniel
> >>
> >> -- [1]
> >>
> >> Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> >> Bus 001 Device 002: ID 0a5c:6410 Broadcom Corp.
> >> Bus 001 Device 003: ID 1bcf:2b95 Sunplus Innovation Technology Inc.
> >> Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
> >
> > Since bus 1 uses an xHCI controller, you should do:
> >
> >         echo 'module xhci-hcd =p' >/sys/kernel/debug/dynamic_debug/control
> >
> > I'm reasonably sure this will end up printing "suspend failed
> > because a port is resuming", since that's the only place where
> > xhci_bus_suspend() fails with -EBUSY, but you should try it to confirm
> > this.
> 
> I had to use:
> echo 'module xhci_hcd =p' >/sys/kernel/debug/dynamic_debug/control
> 
> and indeed we see:
> [29172.246221] xhci_hcd 0000:00:14.0: get port status, actual port 11
> status  = 0xe63
> [29172.246222] xhci_hcd 0000:00:14.0: Get port status returned 0x507
> [29172.246224] xhci_hcd 0000:00:14.0: get port status, actual port 12
> status  = 0x2a0
> [29172.246228] xhci_hcd 0000:00:14.0: get port status, actual port 13
> status  = 0x2a0
> [29172.246228] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246231] xhci_hcd 0000:00:14.0: get port status, actual port 14
> status  = 0x2a0
> [29172.246232] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246235] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246248] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246254] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246264] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246275] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246285] xhci_hcd 0000:00:14.0: Get port status returned 0x507
> [29172.246294] xhci_hcd 0000:00:14.0: get port status, actual port 14
> status  = 0x2a0
> [29172.246302] xhci_hcd 0000:00:14.0: suspend failed because a port is resuming
> [29172.246321] xhci_hcd 0000:00:14.0: Get port status returned 0x107
> [29172.246332] xhci_hcd 0000:00:14.0: get port status, actual port 6
> status  = 0x2a0
> [29172.246346] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246359] xhci_hcd 0000:00:14.0: get port status, actual port 13
> status  = 0x2a0
> [29172.246364] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246366] xhci_hcd 0000:00:14.0: get port status, actual port 15
> status  = 0x2a0
> [29172.246371] xhci_hcd 0000:00:14.0: suspend failed because a port is resuming
> [29172.246380] xhci_hcd 0000:00:14.0: Get port status returned 0x100
> [29172.246382] xhci_hcd 0000:00:14.0: get port status, actual port 1
> status  = 0x2a0
> [29172.246383] xhci_hcd 0000:00:14.0: Get port status returned 0x100

It's time to get some assistance from the xhci-hcd maintainer.

Mathias, Daniel's machine is spinning, trying to suspend the root hub 
on the xHCI HS/FS/LS bus and failing, over and over again.  It looks 
like either bus_state->resuming_ports or bus_state->port_remote_wakeup 
is nonzero when it shouldn't be.

The information we have is all above.  Can you help Daniel debug this?

Alan Stern

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