From: tcamuso@redhat.com <tcamuso@redhat.com>
Date: Mon, 7 Jan 2008 22:15:41 -0500
Subject: [x86] mmconfig: introduce pcibios_fix_bus_scan
Message-id: 20080108031541.15008.51365.sendpatchset@dhcp83-188.boston.redhat.com
O-Subject: [PATCH 5/6][Version-2]PCI: x86 MMCONFIG: introduce pcibios_fix_bus_scan()
Bugzilla: 408551

diff --git a/arch/i386/pci/common.c b/arch/i386/pci/common.c
index 56c9ba4..bf9dffb 100644
--- a/arch/i386/pci/common.c
+++ b/arch/i386/pci/common.c
@@ -29,7 +29,7 @@ struct pci_raw_ops *raw_pci_ops;
 
 #ifdef CONFIG_X86
 int pci_noseg = 0;
-#endif;
+#endif
 
 static int pci_read(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 *value)
 {
@@ -495,3 +495,72 @@ void pcibios_disable_device (struct pci_dev *dev)
 	if (pcibios_disable_irq)
 		pcibios_disable_irq(dev);
 }
+
+/**
+ * This routine traps devices not correctly responding to MMCONFIG access.
+ * For each device on the current bus, compare a mmconf read of the
+ * vendor/device dword with a legacy PCI config read. If they're not the same,
+ * the bus serving this device must use legacy PCI config accesses instead of
+ * mmconf, as must all buses descending from this bus.
+ */
+void __devinit pcibios_fix_bus_scan_quirk(struct pci_bus *bus)
+{
+	int devfn;
+	int fail;
+	int found_nommconf_dev = 0;
+	static int advised;
+	u32 mcfg_vendev;
+	u32 arch_vendev;
+	struct pci_ops *save_ops = bus->ops;
+
+	/*
+	 * Return here if mmconf is NOT the default platform-wide pci config
+	 * access mechanism, or if this bus is within the range checked by
+	 * unreachable_devices().
+	 */
+	if (((pci_probe & PCI_USING_MMCONF) == 0) ||
+	    (bus->number < MAX_CHECK_BUS))
+		return;
+	/*
+	 * If the parent bus has already been programmed for legacy pci config
+	 * access, then there is no need to scan this bus.
+	 */
+	if (bus->parent != NULL)
+		if (bus->parent->ops == &pci_legacy_ops)
+			return;
+
+	if (!advised) {
+		pr_info("PCI: If a device isn't working, "
+			"try \"pci=nommconf\".\n");
+		advised = 1;
+	}
+	pr_debug("PCI: Checking bus %04x:%02x for MMCONFIG compliance.\n",
+		 pci_domain_nr(bus), bus->number);
+
+	for (devfn = 0; devfn < 256; devfn++) {
+		bus->ops = &pci_legacy_ops;
+		fail = pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID,
+						 &arch_vendev);
+		if ((arch_vendev == 0xFFFFFFFF) || (arch_vendev == 0) || fail)
+			continue;
+
+		bus->ops = save_ops;	/* Restore to original value */
+		pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID,
+					  &mcfg_vendev);
+		if (mcfg_vendev != arch_vendev) {
+			found_nommconf_dev = 1;
+			break;
+		}
+	}
+
+	if (found_nommconf_dev) {
+		pr_info("PCI: Device at %04x:%02x.%02x.%x is not MMCONFIG "
+			"compliant.\n", pci_domain_nr(bus), bus->number,
+			PCI_SLOT(devfn), PCI_FUNC(devfn));
+		pr_info("PCI: Bus %04x:%02x and its descendents cannot use "
+			"MMCONFIG.\n", pci_domain_nr(bus), bus->number);
+		bus->ops = &pci_legacy_ops;	/* Use Legacy PCI Config */
+	} else
+		bus->ops = save_ops;		/* Use MMCONFIG  */
+	return;
+}