linux-kernel - Re: `pci_apply_final_quirks()` taking half a second

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Date:   Sun, 31 Dec 2017 16:16:45 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Paul Menzel <pmenzel+linux-pci@...gen.mpg.de>
cc:     Bjorn Helgaas <helgaas@...nel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        <linux-usb@...r.kernel.org>
Subject: Re: `pci_apply_final_quirks()` taking half a second

On Sun, 31 Dec 2017, Paul Menzel wrote:

> Am 29.12.2017 um 17:14 schrieb Alan Stern:
> > On Thu, 28 Dec 2017, Bjorn Helgaas wrote:
> > 
> >> On Tue, Dec 26, 2017 at 04:55:20PM +0100, Paul Menzel wrote:
> >>> Am 08.04.2017 um 17:41 schrieb Bjorn Helgaas:
> >>>> On Fri, Apr 07, 2017 at 11:07:15PM +0200, Paul Menzel wrote:
> >>>
> >>>>> Measuring where time is spent during boot with `systemd-bootchart`
> >>>>> on an Asus A780FullHD, it turns out that half a second is spent in
> >>>>> `pci_apply_final_quirks()`.
> >>>>
> >>>> I agree, that seems like a crazy amount of time.
> >>>>
> >>>> Can you figure out how to turn on pr_debug() (via the dynamic debug
> >>>> mess or whatever) and boot with "initcall_debug"?  That should tell us
> >>>> how long each quirk took.
> >>>
> >>> I am sorry for taking so long to reply. I finally added `dyndbg=file
> >>> quirks.c +p` to the command line of Linux 4.13.13. This is on
> >>> another AMD system (Asus F285M Pro).

> >>> Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> >>> quirk_usb_early_handoff+0x0/0x6b0 returned after 88643 usecs for
> >>> 0000:00:12.0

> >>> Dez 26 16:21:46 asus-f2a85-pro kernel: pci fixup
> >>> quirk_usb_early_handoff+0x0/0x6b0 returned after 85770 usecs for
> >>> 0000:00:13.0

> >>> So it’s `pci fixup quirk_usb_early_handoff` taking around 85 ms, and
> >>> that twice.
> >>
> >> Wow.  That's pretty painful, but of course I don't know how to fix it.
> >>  From looking at quirk_usb_early_handoff(), it may depend on BIOS
> >> details.  Maybe the USB folks will have some ideas.
> > 
> > Can we see the output from lspci?  It would help to know what the 12.0
> > and 13.0 devices are.
> 
> Sorry, that was trimmed from the original message. Here is the output 
> from the ASRock A780FullD.
> 
> > ```
> > $ more /proc/version
> > Linux version 4.9.0-0.bpo.2-amd64 (debian-kernel@...ts.debian.org)
> > (gcc version 4.9.2 (Debian 4.9.2-10) ) #1 SMP Debian 4.9.13-1~bpo8+1 (2017-02-27)
> > $ lspci -nn

> > 00:12.0 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller [1002:4397]
> > 00:12.1 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0 USB OHCI1 Controller [1002:4398]
> > 00:12.2 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller [1002:4396]
> > 00:13.0 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB OHCI0 Controller [1002:4397]
> > 00:13.1 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0 USB OHCI1 Controller [1002:4398]
> > 00:13.2 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 USB EHCI Controller [1002:4396]

> So far, this can be reproduce on all AMD systems I have (ASRock 
> A780FullHD, ASRock E350M1, Asus F2A85-M Pro).

So they are OHCI controllers.  You could add some debugging statements 
to quirk_usb_handoff_ohci() to try and locate the part that's taking so 
long.

It's also worth mentioning that the same source file contains lots of 
special-case code for AMD and ASmedia hardware.  I don't know whether 
any of it is involved in the long time delays you are seeing, however.

Alan Stern