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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH] Register usb-uhci reset function.
Date: Tue, 16 Jun 2009 18:14:57 +0100
References: <20090616124702.GS19508@redhat.com>
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To: qemu-devel@nongnu.org
Cc: Gleb Natapov <gleb@redhat.com>

On Tuesday 16 June 2009, Gleb Natapov wrote:
> Update irq line on reset. Reseting irq line is required because
> racing irq from pci device will call piix3_set_irq(). piix3_set_irq()
> will remember current level in pci_irq_levels[]. The PIC line will be
> triggered if one of pci_irq_levels[] is set (depends on piix3 config).
> If for instance pci_irq_levels[0] and pci_irq_levels[1] are mapped to
> the same PIC irq and during reset pci_irq_levels[1] == 1, but device
> that drives pci_irq_levels[0] is initialized first the device driver
> will not be able to lower irq line.

This is nonsense.

The only relevant circumstances are if the devices raises an IRQ, and is then 
reset by software while the system is running. It's got nothing to do with 
piix3, PCI bus interrupt sharing or system reset. If you are seeing problems 
after a system reset then your bug lies elsewhere.

Paul