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Date
SubjectRe: [patch] PCI: disable MSI on more ATI NorthBridges
From
From: Daniel Barkalow <barkalow@iabervon.org>
Date: Mon, 22 Oct 2007 17:31:04 -0400 (EDT)

> It's likewise documented (although maybe arguable in wording) that the
> device shouldn't send legacy interrupts if MSI is in use, regardless of
> INTX_DISABLE, but this also happens in the field.
>
> I think that the current Linux behavior with respect to INTX_DISABLE is
> simply due to which hardware bug was present in the device whose driver
> first got Linux support, but one or the other or both needs a quirk, since
> there's no behavior that works with everything. And it's still impossible
> to tell which bug is more common, since MSI isn't used most of the time,
> even if the hardware supports it, so it's pretty arbitrary which way Linux
> goes in the non-quirk case.

I think this pretty much sums up the situation accurately.

My suggestion is:

1) Leave the pci_intx() twiddling code in drivers/pci/msi.c

2) Add quirks for "INTX_DISABLE turns off MSI too", this sets
a flag in the pci_dev.

3) The pci_intx() calls in drivers/pci/msi.c are skipped if this
flag from #2 is set.

4) Add quirk entries for drivers/net/tg3.c chips and these SATA
devices we are learning about here, as well as any others we
are aware of right now.

5) Remove the pci_intx() workaround code from drivers/net/tg3.c
and elsewhere.
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