Re: [PATCH] 2.6 SGI Altix I/O code reorganization

From: Colin Ngam <>
Date: 2004-10-07 05:09:54
Grant Grundler wrote:

> On Wed, Oct 06, 2004 at 10:32:23AM -0500, Patrick Gefre wrote:
> > o added our own pci_ops (Grant/Matthew's request)
> Sorry - my bad.
> I confused the issue by claiming one should replace pci_root_ops.
> It was one possibility but it's not an easy path to take.

Hi Grant,

> Mathew explained replacing the raw_pci_ops pointer is the Right Thing
> and I suspect it's easier to properly implement.

I believe we did just that.  We did not touch pci_root_ops.

> Some comments on the implementation:
> o sn_pci_fixup_bus() is a confusing name. "pcibios_fixup_bus" is normally
>   called by generic PCI code after each bus is walked.
>   This code obviously doesn't support that.
>   Maybe, sn_init_pci_controller() or something like that would be clearer.

That is a good idea and can be done.

> o This bit of code belongs in the pcibios_fixup_bus() call path:
>         +       /*
>         +        * Generic Linux PCI Layer has created the pci_bus and pci_dev
>         +        * structures - time for us to add our SN PLatform specific
>         +        * information.
>         +        */
>         +
>         +       while ((pci_dev =
>         +               pci_find_device(PCI_ANY_ID, PCI_ANY_ID, pci_dev)) != NULL) {
>         +               sn_pci_fixup_slot(pci_dev);
>         +       }
>   I realize that's not easy to add/maintain in the arch/ia64 port though
>   since pcibios_fixup_bus() is common code for multiple platforms.

Yes, would anybody allow us to make a platform specific callout from within generic

> o sn_pci_fixup_bus() should be called for each PCI root bus controller
>   the firmware advertises. The loop in sn_pci_init() is hard coded
>   to loop from 0 to 256 busses.
>   Is ACPI the only way PCI host controllers are advertised?

That would be my assumption.  And ACPI is our next effort.

>   SN2 doesn't use a different method today?


>   It means we are telling PCI subsystem to walk root busses that don't
>   exist in all configurations. I hope there are no nasty side effects
>   from that.

Not at all.  If you look at the loop, sn_pci_fixup_bus(0 gets called for 0 -
PCI_BUSES_TO_SCAN but if the bus does not exist, we do not call pci_scan_bus(),
therefore the PCI subsystem is not called to walk buses that do not exist on SN.

> o the BUG() in:
>         +       controller = sn_alloc_pci_sysdata();
>         +       if (!controller) {
>         +               BUG();
>         +       }
>   is redundant with the BUG in sn_alloc_pci_sysdata().

Thanks.  We can fix this.

One favour.  Would you agree to letting this patch be included by Tony and we will come
up with another patch to fix the 2 obvious items listed above?  It will be great to
avoid spinning this big patch.



> sorry for the initial bad advice and I hope this helps,
> grant
> -
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Received on Wed Oct 6 15:27:39 2004

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