Re: [PATCH] PCI: fall back to original BIOS BAR addresses

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On Thu, 15 Jul 2010 09:41:42 -0600
Bjorn Helgaas <bjorn.helgaas@xxxxxx> wrote:

> 
> If we fail to assign resources to a PCI BAR, this patch makes us try
> the original address from BIOS rather than leaving it disabled.
> 
> Linux tries to make sure all PCI device BARs are inside the upstream
> PCI host bridge or P2P bridge apertures, reassigning BARs if
> necessary. Windows does similar reassignment.
> 
> Before this patch, if we could not move a BAR into an aperture, we
> left the resource unassigned, i.e., at address zero.  Windows leaves
> such BARs at the original BIOS addresses, and this patch makes Linux
> do the same.
> 
> This is a bit ugly because we disable the resource long before we try
> to reassign it, so we have to keep track of the BIOS BAR address
> somewhere. For lack of a better place, I put it in the struct pci_dev.
> 
> I think it would be cleaner to attempt the assignment immediately
> when the claim fails, so we could easily remember the original
> address.  But we currently claim motherboard resources in the middle,
> after attempting to claim PCI resources and before assigning new PCI
> resources, and changing that is a fairly big job.
> 
> Addresses https://bugzilla.kernel.org/show_bug.cgi?id=16263
> 
> Reported-by: Andrew <nitr0@xxxxxxxxxx>
> Tested-by: Andrew <nitr0@xxxxxxxxxx>
> Signed-off-by: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
> ---

Nice, I'll see if Linus will take this before 2.6.35 comes out.

Jesse
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