From cf1a4cf8754afb248e498815c7957aeb4faca79f Mon Sep 17 00:00:00 2001 From: Gavin Shan Date: Sun, 3 Jun 2012 22:15:25 +0000 Subject: powerpc/pci: Save P2P bridge resource if possible When PCI probe flag PCI_REASSIGN_ALL_RSRC has been passed into PCI core, it's hoped that all resources to be reassigned by PCI core. As to particular P2P (PCI-to-PCI) bridge, the size of the corresponding BAR (I/O, MMIO, prefetchable MMIO) is calculated by the resources required by the PCI devices behind the P2P bridge. That means that the information like start/end address retrieved from the hardware registers of the P2P bridge is meainingless in the case. However, we still count that in and the BARs might have been configured by firmware with non-zero size. That leads to space waste. The patch explicitly sets the size of P2P bridge BARs to zero in case that resource reassignment is expected with PCI probe flag PCI_REASSIGN_ALL_RSRC. In the result, it will save overall resource required by the system without waste. Signed-off-by: Gavin Shan Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/pci-common.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'arch/powerpc/kernel/pci-common.c') diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c index 2aa04f29e1d..4cb714792be 100644 --- a/arch/powerpc/kernel/pci-common.c +++ b/arch/powerpc/kernel/pci-common.c @@ -960,13 +960,14 @@ static void __devinit pcibios_fixup_bridge(struct pci_bus *bus) if (i >= 3 && bus->self->transparent) continue; - /* If we are going to re-assign everything, mark the resource - * as unset and move it down to 0 + /* If we're going to reassign everything, we can + * shrink the P2P resource to have size as being + * of 0 in order to save space. */ if (pci_has_flag(PCI_REASSIGN_ALL_RSRC)) { res->flags |= IORESOURCE_UNSET; - res->end -= res->start; res->start = 0; + res->end = -1; continue; } @@ -1228,7 +1229,14 @@ void pcibios_allocate_bus_resources(struct pci_bus *bus) pr_warning("PCI: Cannot allocate resource region " "%d of PCI bridge %d, will remap\n", i, bus->number); clear_resource: - res->start = res->end = 0; + /* The resource might be figured out when doing + * reassignment based on the resources required + * by the downstream PCI devices. Here we set + * the size of the resource to be 0 in order to + * save more space. + */ + res->start = 0; + res->end = -1; res->flags = 0; } -- cgit v1.2.3