RE: MSI fix for buggy PCI/PCI-X hardware

[Nakajima, Jun]

Jeff, Hi.

How about the default behavior? I'm not a fan of disable_msi(), because
we need to update the driver as we find problems, and we cannot predict
which PCI/PCI-X devices in the world have such a problem, although we
know some will. The workaround in drivers/pci/quirk.c is much better,
compared to modifying the driver, but we still need to update the file
(and rebuild the kernel) as we find problems.

In my opinion, we might want to use drivers/pci/quirk.c to blacklist PCI
Express devices if any (hope not). For PCI/PCI-X devices, we might want
to enable MSI once verified for it. To that end we can also use
drivers/pci/quirk.c to whitelist them (or it's abuse?). That way we can
avoid situations like "it hangs, it does not get interrupts", "disable
ACPI, oh no, MSI".

Thanks,
Jun

> -----Original Message-----
> From: Jeff Garzik [mailto:jgarzik@xxxxxxxxx]
> Sent: Tuesday, September 09, 2003 11:41 AM
> To: long
> Cc: linux-kernel@xxxxxxxxxxxxxxx; greg@xxxxxxxxx; Nakajima, Jun;
Nguyen,
> Tom L; zwane@xxxxxxxxxxxxx
> Subject: Re: MSI fix for buggy PCI/PCI-X hardware
> 
> On Tue, Sep 09, 2003 at 08:39:37AM -0700, long wrote:
> > The proposed solution is to provide a new API, named "int
> > disable_msi(struct pci_dev *dev)", to allow IHV's who have
> > shipped PCI/PCI-X hardware that does not work in MSI mode to update
> > their software drivers to request the kernel to switch the
> > interrupt mode from MSI mode back to IRQ pin-assertion mode.
> 
> No need for a new API.  We have drivers/pci/quirk.c where we add PCI
> devices with known bugs.  If there is commonality of the bugs across
> hardware, we can easily add a common "quirk" which fixes the
situation.
> 
> Individual drivers shouldn't need to bother with this, really.
> 
> As an aside, if you need to blacklist certain _systems_ rather than
> certain PCI devices, you should either modify drivers/pci/quirks.c or
> arch/i386/kernel/dmi_scan.c.
> 
> 	Jeff
> 
> 

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