PCI: Claim ACS support for AMD southbridge devices

AMD confirmed that peer-to-peer between these devices is
not possible.  We can therefore claim that they support a
subset of ACS.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Donald Dutile <ddutile@redhat.com>

drivers/pci/quirks.c

@@ -3295,11 +3295,61 @@ struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
 	return pci_dev_get(dev);
 }
 
+/*
+ * AMD has indicated that the devices below do not support peer-to-peer
+ * in any system where they are found in the southbridge with an AMD
+ * IOMMU in the system.  Multifunction devices that do not support
+ * peer-to-peer between functions can claim to support a subset of ACS.
+ * Such devices effectively enable request redirect (RR) and completion
+ * redirect (CR) since all transactions are redirected to the upstream
+ * root complex.
+ *
+ * http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/94086
+ * http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/94102
+ * http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/99402
+ *
+ * 1002:4385 SBx00 SMBus Controller
+ * 1002:439c SB7x0/SB8x0/SB9x0 IDE Controller
+ * 1002:4383 SBx00 Azalia (Intel HDA)
+ * 1002:439d SB7x0/SB8x0/SB9x0 LPC host controller
+ * 1002:4384 SBx00 PCI to PCI Bridge
+ * 1002:4399 SB7x0/SB8x0/SB9x0 USB OHCI2 Controller
+ */
+static int pci_quirk_amd_sb_acs(struct pci_dev *dev, u16 acs_flags)
+{
+#ifdef CONFIG_ACPI
+	struct acpi_table_header *header = NULL;
+	acpi_status status;
+
+	/* Targeting multifunction devices on the SB (appears on root bus) */
+	if (!dev->multifunction || !pci_is_root_bus(dev->bus))
+		return -ENODEV;
+
+	/* The IVRS table describes the AMD IOMMU */
+	status = acpi_get_table("IVRS", 0, &header);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	/* Filter out flags not applicable to multifunction */
+	acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
+
+	return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
+#else
+	return -ENODEV;
+#endif
+}
+
 static const struct pci_dev_acs_enabled {
 	u16 vendor;
 	u16 device;
 	int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
 } pci_dev_acs_enabled[] = {
+	{ PCI_VENDOR_ID_ATI, 0x4385, pci_quirk_amd_sb_acs },
+	{ PCI_VENDOR_ID_ATI, 0x439c, pci_quirk_amd_sb_acs },
+	{ PCI_VENDOR_ID_ATI, 0x4383, pci_quirk_amd_sb_acs },
+	{ PCI_VENDOR_ID_ATI, 0x439d, pci_quirk_amd_sb_acs },
+	{ PCI_VENDOR_ID_ATI, 0x4384, pci_quirk_amd_sb_acs },
+	{ PCI_VENDOR_ID_ATI, 0x4399, pci_quirk_amd_sb_acs },
 	{ 0 }
 };