PCI: work around Stratus ftServer broken PCIe hierarchy

A PCIe downstream port is a P2P bridge.  Its secondary interface is
a link that should lead only to device 0 (unless ARI is enabled)[1], so
we don't probe for non-zero device numbers.

Some Stratus ftServer systems have a PCIe downstream port (02:00.0) that
leads to both an upstream port (03:00.0) and a downstream port (03:01.0),
and 03:01.0 has important devices below it:

  [0000:02]-+-00.0-[03-3c]--+-00.0-[04-09]--...
                            \-01.0-[0a-0d]--+-[USB]
                                            +-[NIC]
                                            +-...

Previously, we didn't enumerate device 03:01.0, so USB and the network
didn't work.  This patch adds a DMI quirk to scan all device numbers,
not just 0, below a downstream port.

Based on a patch by Prarit Bhargava.

[1] PCIe spec r3.0, sec 7.3.1

CC: Myron Stowe <mstowe@redhat.com>
CC: Don Dutile <ddutile@redhat.com>
CC: James Paradis <james.paradis@stratus.com>
CC: Matthew Wilcox <matthew.r.wilcox@intel.com>
CC: Jesse Barnes <jbarnes@virtuousgeek.org>
CC: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

arch/x86/pci/common.c

@@ -11,6 +11,7 @@
 #include <linux/dmi.h>
 #include <linux/slab.h>
 
+#include <asm-generic/pci-bridge.h>
 #include <asm/acpi.h>
 #include <asm/segment.h>
 #include <asm/io.h>
@@ -229,6 +230,14 @@ static int __devinit assign_all_busses(const struct dmi_system_id *d)
 }
 #endif
 
+static int __devinit set_scan_all(const struct dmi_system_id *d)
+{
+	printk(KERN_INFO "PCI: %s detected, enabling pci=pcie_scan_all\n",
+	       d->ident);
+	pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
+	return 0;
+}
+
 static const struct dmi_system_id __devinitconst pciprobe_dmi_table[] = {
 #ifdef __i386__
 /*
@@ -420,6 +429,13 @@ static const struct dmi_system_id __devinitconst pciprobe_dmi_table[] = {
 			DMI_MATCH(DMI_PRODUCT_NAME, "ProLiant DL585 G2"),
 		},
 	},
+	{
+		.callback = set_scan_all,
+		.ident = "Stratus/NEC ftServer",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "ftServer"),
+		},
+	},
 	{}
 };