Re: [coreboot] disabling bios usb stack

[Scott Duplichan]

ron minnich [mailto:[e-mail]] wrote:

]Thanks scott!
]
]So, what does an OS do to disable USB in the operating system? We have
]seen Linux do it, we're not quite sure just what
]place it gets done.
]
]ron

If I understand your question, I am not sure I know the answer. If you
boot linux with grub option 'nousb', or reboot Windows after disabling
usb controllers from device manager, what happens? I assume the operating
system just ignores USB controllers. It seems unlikely that the OS would
take some action to ensure that they are properly disabled. Does UEFI
disable USB controllers before handoff to the OS loader? I do not know.
Having the OS not load USB drivers should eliminate USB related interrupts,
but I know EHCI can generate memory accesses even when idle.

Thanks,
Scott

disabling bios usb stack

[ron minnich]

The guys found it, bit in southbridge to enable SMI interrupts, they
turned it off and are now seeing a 40 hz. interrupt. It never ends.