RE: How to find if BIOS has already enabled the device

[Aleksey Gorelov]

>I am trying to trace the root cause of an annoying problem 
>with a USB Storage 
>device - 
>
>My laptop's BIOS supports booting from USB devices. I have attached an 
>external USB HDD to a USB 2.0 port. If I boot Linux with the 
>HDD attached and 
>powered on, load of OHCI-HCD module hangs the machine for 
>around 2 minutes - 
>after that it recovers and all is fine. I have tried different distros 
>without luck, but while installing debian, I figured out that the hang 
>happens after ohci-hcd calls pci_enable_device() for the USB 
>controller.
>
>This does not happen when the boot is complete. I.e. if I 
>attach the HDD after 
>boot is complete (BIOS did not get a chance to enable it 
>beforehand) load of 
>ohci-hcd (during and after boot) does not hang the machine.
>
>I think since the machine supports booting from USB HDD, the 
>BIOS must be 
>enabling the USB controller and attached device early during 
>boot, and when 
>ohci-hcd tries to re-enable it, it doesn't like it and leads 
>to a hang. 

See if 'usb-handoff' as a kernel parameter makes it any better.

Aleks.

>
>My question - Is it possible to detect if the USB controller 
>is already 
>enabled and skip enabling it second time?
>
>Thanks
>
>Parag
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