linux-kernel - Re: ohci1394 problem (MMIO broken) (was 2.6.25-rc6-git6: Reported regressions from 2.6.24) [Bug 10080]

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Message-ID: <47E587E8.4050103@s5r6.in-berlin.de>
Date:	Sat, 22 Mar 2008 23:27:52 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	"H. Peter Anvin" <hpa@...nel.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Thomas Meyer <thomas@...3r.de>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Natalie Protasevich <protasnb@...il.com>,
	bugme-daemon@...zilla.kernel.org
Subject: Re: ohci1394 problem (MMIO broken) (was 2.6.25-rc6-git6: Reported
 regressions from 2.6.24) [Bug 10080]

H. Peter Anvin wrote at 
http://bugzilla.kernel.org/show_bug.cgi?id=10080#c9 :
> I'm confused about this.  I looked at the original threads, and what really
> stands out to me is that the original reporter had two drivers loaded for the
> same hardware (firewire-ohci and ohci1394.)  *In the best case* there is a
> fundamental race condition there, meaning unpredictable behaviour would be the
> norm.

Hmm, right -- I didn't see this until now.  Today's dmesg:
http://bugzilla.kernel.org/attachment.cgi?id=15397&action=view
[    1.236587] firewire_ohci: Failed to remap registers
[  243.640549] ohci1394: fw-host0: Get PHY Reg timeout
(etc.)

However, the two drivers for the same device don't seem to be the 
problem.  Looks like firewire-ohci was attempted to be bound to the 
controller much earlier than ohci1394.  The error message means that 
firewire-ohci's pci_request_region() succeeded but pci_iomap() failed, 
hence the pci_driver.probe failed, hence firewire-ohci wasn't bound to 
the device, hence subsequent loading of ohci1394 (manually, I presume) 
was a valid action.

IOW firewire-ohci was indeed already loaded, but not bound to the device 
because of the .probe failure; and ohci1394 was loaded much later.

Same thing in the report in February:
http://lkml.org/lkml/2008/2/23/244
[    1.326958] firewire_ohci: Failed to remap registers
[  856.943807] ohci1394: fw-host0: Get PHY Reg timeout
(here: ohci1394 manually loaded by insmod)

(Let's see if bugme-daemon captures this...)
-- 
Stefan Richter
-=====-==--- --== =-==-
http://arcgraph.de/sr/
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