[PATCH] PCI: handle subtractive decode pci-pci bridge better

With the number of PCI bus resources increased to 8, we can
handle the subtractive decode PCI-PCI bridge like a normal
bridge, taking into account standard PCI-PCI bridge windows
(resources 0-2). This helps to avoid problems with peer-to-peer DMA
behind such bridges, poor performance for MMIO ranges outside bridge
windows and prefetchable vs. non-prefetchable memory issues.

To reflect the fact that such bridges do forward all addresses to
the secondary bus (transparency), remaining bus resources 3-7 are
linked to resources 0-4 of the primary bus. These resources will be
used as fallback by resource management code if allocation from
standard bridge windows fails for some reason.

Signed-off-by: Ivan Kokshaysky <[e-mail]>
Acked-by: Dominik Brodowski <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/pci/probe.c

···
 
 	if (dev->transparent) {
 		printk(KERN_INFO "PCI: Transparent bridge - %s\n", pci_name(dev));
-		for(i = 0; i < PCI_BUS_NUM_RESOURCES; i++)
-			child->resource[i] = child->parent->resource[i];
-		return;
+		for(i = 3; i < PCI_BUS_NUM_RESOURCES; i++)
+			child->resource[i] = child->parent->resource[i - 3];
 	}
 
 	for(i=0; i<3; i++)