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Subject: RE: How to find if BIOS has already enabled the device
Date: Fri, 27 May 2005 18:34:50 -0700
Message-ID: <0EF82802ABAA22479BC1CE8E2F60E8C31B5206@scl-exch2k3.phoenix.com>
Thread-Topic: How to find if BIOS has already enabled the device
Thread-Index: AcVjHXRDo+2KyjjBSjGOpIC8EOiAdgAB6+8A
From: "Aleksey Gorelov" <Aleksey_Gorelov@Phoenix.com>
To: "Parag Warudkar" <kernel-stuff@comcast.net>,
       <linux-kernel@vger.kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1727
Lines: 51

>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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