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Message-ID: <19142.21600.475756.10647@pilspetsen.it.uu.se>
Date: Fri, 2 Oct 2009 21:28:32 +0200
From: Mikael Pettersson <mikpe@it.uu.se>
To: Mikael Pettersson <mikpe@it.uu.se>
Cc: Nick Piggin <npiggin@suse.de>, David Woodhouse <dwmw2@infradead.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Patch "USB: Work around BIOS bugs by quiescing USB controllers earlier" causes MCEs
In-Reply-To: <19141.54587.207559.849751@pilspetsen.it.uu.se>
References: <20091002073400.GV6327@wotan.suse.de>
	<19141.54587.207559.849751@pilspetsen.it.uu.se>
Sender: linux-kernel-owner@vger.kernel.org
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Mikael Pettersson writes:
 > Nick Piggin writes:
 >  > Hi,
 >  > 
 >  > Your patch db8be50c4307dac2b37305fc59c8dc0f978d09ea is causing my
 >  > ia64 Altix system to die with an MCE in early boot.
 > 
 > The same commit has been confirmed by two people on the ARM list
 > to cause boot failures on two different Intel XScale IOP machines.
 > The machines have serial consoles, but only show
 > 
 > Uncompressing Linux... done. Booting the kernel.
 > 
 > before they hang.

I've just investigated this on one of my ARM boxes that this commit kills.

The commit changed quirk_usb_early_handoff to be a FIXUP_HEADER, which
caused it to be invoked during the early stages of the platform's PCI
init (arch/arm/kernel/bios32.c). quirk_usb_handoff_uhci() gets a bogus
I/O base address, passes that down to uhci_reset_hc(), causing a kernel
page fault in the first "outw(UHCI_USBCMD_HCRESET, base + UHCI_USBCMD);",
causing the kernel to oops.

(All this occurs before the serial console works, so I had to add a
platform-specific puts() and lots of tracing statements.)

Changing this quirk back to a FIXUP_FINAL allows the platform's PCI
init to complete. Later on the generic pci_init() calls the quirk,
which now gets the correct I/O base address, and the outw()s in
uhci_reset_hc() don't fail.
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