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From: Peter Maydell <peter.maydell@linaro.org>
Date: Tue, 14 May 2013 12:45:57 +0100
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Subject: Re: [Qemu-devel] [PATCH v2 07/11] versatile_pci: Implement the
	correct PCI IRQ mapping
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To: Arnd Bergmann <arnd@arndb.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, patches@linaro.org, Will Deacon <will.deacon@arm.com>, qemu-devel@nongnu.org, Paul Brook <paul@codesourcery.com>, =?UTF-8?Q?Andreas_F=C3=A4rber?= <afaerber@suse.de>, Aurelien Jarno <aurelien@aurel32.net>

On 26 March 2013 11:08, Arnd Bergmann <arnd@arndb.de> wrote:
> On Tuesday 26 March 2013, Peter Maydell wrote:
>>
>> On 26 March 2013 10:54, Arnd Bergmann <arnd@arndb.de> wrote:
>> > Yes, very good.  We will probably introduce sparse irq support on
>> > versatile in the near future, and then the value we write into the
>> > PCI_INTERRUPT_LINE field will become arbitrary from qemu's point
>> > of view, but I will make sure that we fix the interrupt mapping
>> > in the kernel at the same time so we always fall into the
>> > "s->broken_irq_mapping = false;" case.
>>
>> Yeah, as long as you avoid the number 27 you're ok :-)
>
> Good point. I guess we'll have to keep using a legacy domain for
> versatile then.

So there turns out to be a problem with this. Newer
kernels (I'm looking at current mainline master) write
a number other than 27 (in this case 94) to the
PCI_INTERRUPT_LINE register, but they still assume the
old broken IRQ mapping. So our "autodetect busted kernels"
code doesn't work.

I've also discovered that there are some kernels (including
current master) which don't like it when the host PCI bridge
goes at slot 29 like it does on real hardware; so I think
I'll just have to revert that patch.

-- PMM