The following reply was made to PR usb/156596; it has been noted by GNATS.

From: Colin Percival <cperc...@freebsd.org>
To: Hans Petter Selasky <hsela...@c2i.net>
Cc: "bug-follo...@freebsd.org" <bug-follo...@freebsd.org>
Subject: Re: usb/156596: [ehci] Extremely high interrupt rate on ehci/uhci
 IRQ16 80% cpu utilization on CPU0
Date: Sun, 10 Jul 2011 18:30:22 -0700

 On 07/09/11 02:07, Hans Petter Selasky wrote:
 > Have you tried to set any of these quirks:
 > 
 > hw.usb.ehci.lostintrbug: 0
 > hw.usb.ehci.iaadbug: 0
 
 Yes.  Neither has any effect.  (At least, not when I set them via sysctl; I
 could try setting them as loader tunables if you think that would make a
 difference.)
 
 I wrote:
 > The attached patch seems to fix the problem while not breaking anything on
 > my laptop.
 
 Key words, "seems to".  On further use I've found that my change didn't make
 any difference; it was just a coincidence that the problem temporarily went
 away at that time.
 
 However, I've managed (I think!) to figure out what's triggering this: The
 IRQ flood starts when the laptop battery is recharging.  Letting the battery
 run down for a couple hours and then plugging in AC power has 100% consistently
 triggered this; but if the battery is already fully charged when FreeBSD boots
 I don't get the IRQ flood.
 
 Hans Petter Selasky wrote:
 > Try the attached patch and report back. The EHCI should never generate more 
 > than 8000 IRQ/s second, so this clearly indicates a Hardware Problem.
 
 No change, I'm afraid.
 
 -- 
 Colin Percival
 Security Officer, FreeBSD | freebsd.org | The power to serve
 Founder / author, Tarsnap | tarsnap.com | Online backups for the truly paranoid
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