Date: Wed, 15 Aug 2012 12:27:49 -0400 From: Paul Mather <paul@gromit.dlib.vt.edu> To: stable@freebsd.org Subject: uhci0 excessive interrupts---how can I disable or reset specific USB port? Message-ID: <6DFEFF91-F9A9-4C64-8D1C-FB7A73BC7A2E@gromit.dlib.vt.edu>
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I am running FreeBSD/amd64 9-STABLE (built Mon Jul 23 10:45:51 EDT 2012) = on a Dell Optiplex 760 and, today, noticed I had almost 30% system CPU = load in top even when the system was idle. A perusal of vmstat revealed = the cause to be excessive interrupts on uhci0, even though nothing was = plugged into that USB port: # vmstat -i interrupt total rate irq4: uart0 22 0 irq16: uhci0 617002282738 310969 irq23: uhci3 ehci1 83 0 irq256: hpet0:t0 135818421 68 irq257: hpet0:t1 2222659301 1120 irq264: em0 29529304 14 irq265: ahci0 11132506 5 Total 619401422375 312178 Because I am only using the front USB ports on that hardware, I thought = I would disable the other (rear) USB ports in the BIOS. I rebooted and = duly disabled them. However, when FreeBSD booted, it appeared to ignore = the BIOS setting: all the USB ports were probed as usual. (The high = interrupts had vanished, though that might have been due to FreeBSD = correctly shutting down the controllers at shutdown, or just the act of = rebooting itself.) I added "hint.uhci.0.disabled=3D1" to /boot/loader.conf (hoping it would = disable uhci0), but, again all the USB ports appeared in the boot = probes. (However, it *appears* as if uhci0 has been disabled because = the "irq16: uhci0" line no longer appears in "vmstat -i". However, all = the same ugen devices appear in /dev.) Is there a way of disabling a specific USB controller that you don't = want to use? If so, how? I looked at usbconfig, but that appears to me = to be more about controlling devices plugged in to a USB port rather = than the port itself. The "reset" command of usbconfig appears to be = about resetting USB devices, not ports. If I can't disable a specific USB port, is there a way to reset it = without rebooting? If I ever get another crazy interrupt storm like I = noticed today it would be nice to be able to stop it without having to = do a reboot. Cheers, Paul.
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