PCI: support PCIe ARI capability

This patch adds support for PCI Express Alternative Routing-ID
Interpretation (ARI) capability.

The ARI capability extends the Function Number field of the PCI Express
Endpoint by reusing the Device Number which is otherwise hardwired to 0.
With ARI, an Endpoint can have up to 256 functions.
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pci.c

@@ -1299,6 +1299,38 @@ void pci_pm_init(struct pci_dev *dev)
 	}
 }
 
+/**
+ * pci_enable_ari - enable ARI forwarding if hardware support it
+ * @dev: the PCI device
+ */
+void pci_enable_ari(struct pci_dev *dev)
+{
+	int pos;
+	u32 cap;
+	u16 ctrl;
+
+	if (!dev->is_pcie)
+		return;
+
+	if (dev->pcie_type != PCI_EXP_TYPE_ROOT_PORT &&
+	    dev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM)
+		return;
+
+	pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
+	if (!pos)
+		return;
+
+	pci_read_config_dword(dev, pos + PCI_EXP_DEVCAP2, &cap);
+	if (!(cap & PCI_EXP_DEVCAP2_ARI))
+		return;
+
+	pci_read_config_word(dev, pos + PCI_EXP_DEVCTL2, &ctrl);
+	ctrl |= PCI_EXP_DEVCTL2_ARI;
+	pci_write_config_word(dev, pos + PCI_EXP_DEVCTL2, ctrl);
+
+	dev->ari_enabled = 1;
+}
+
 int
 pci_get_interrupt_pin(struct pci_dev *dev, struct pci_dev **bridge)
 {

drivers/pci/pci.h

@@ -151,4 +151,16 @@ struct pci_slot_attribute {
 };
 #define to_pci_slot_attr(s) container_of(s, struct pci_slot_attribute, attr)
 
+extern void pci_enable_ari(struct pci_dev *dev);
+/**
+ * pci_ari_enabled - query ARI forwarding status
+ * @dev: the PCI device
+ *
+ * Returns 1 if ARI forwarding is enabled, or 0 if not enabled;
+ */
+static inline int pci_ari_enabled(struct pci_dev *dev)
+{
+	return dev->ari_enabled;
+}
+
 #endif /* DRIVERS_PCI_H */

drivers/pci/probe.c

@@ -1025,6 +1025,9 @@ static void pci_init_capabilities(struct pci_dev *dev)
 
 	/* Vital Product Data */
 	pci_vpd_pci22_init(dev);
+
+	/* Alternative Routing-ID Forwarding */
+	pci_enable_ari(dev);
 }
 
 void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)

include/linux/pci.h

@@ -214,6 +214,7 @@ struct pci_dev {
 	unsigned int	broken_parity_status:1;	/* Device generates false positive parity */
 	unsigned int 	msi_enabled:1;
 	unsigned int	msix_enabled:1;
+	unsigned int	ari_enabled:1;	/* ARI forwarding */
 	unsigned int	is_managed:1;
 	unsigned int	is_pcie:1;
 	pci_dev_flags_t dev_flags;

include/linux/pci_regs.h

@@ -419,6 +419,10 @@
 #define  PCI_EXP_RTCTL_CRSSVE	0x10	/* CRS Software Visibility Enable */
 #define PCI_EXP_RTCAP		30	/* Root Capabilities */
 #define PCI_EXP_RTSTA		32	/* Root Status */
+#define PCI_EXP_DEVCAP2		36	/* Device Capabilities 2 */
+#define  PCI_EXP_DEVCAP2_ARI	0x20	/* Alternative Routing-ID */
+#define PCI_EXP_DEVCTL2		40	/* Device Control 2 */
+#define  PCI_EXP_DEVCTL2_ARI	0x20	/* Alternative Routing-ID */
 
 /* Extended Capabilities (PCI-X 2.0 and Express) */
 #define PCI_EXT_CAP_ID(header)		(header & 0x0000ffff)
@@ -429,6 +433,7 @@
 #define PCI_EXT_CAP_ID_VC	2
 #define PCI_EXT_CAP_ID_DSN	3
 #define PCI_EXT_CAP_ID_PWR	4
+#define PCI_EXT_CAP_ID_ARI	14
 
 /* Advanced Error Reporting */
 #define PCI_ERR_UNCOR_STATUS	4	/* Uncorrectable Error Status */
@@ -536,5 +541,14 @@
 #define HT_CAPTYPE_GEN3		0xD0	/* Generation 3 hypertransport configuration */
 #define HT_CAPTYPE_PM		0xE0	/* Hypertransport powermanagement configuration */
 
+/* Alternative Routing-ID Interpretation */
+#define PCI_ARI_CAP		0x04	/* ARI Capability Register */
+#define  PCI_ARI_CAP_MFVC	0x0001	/* MFVC Function Groups Capability */
+#define  PCI_ARI_CAP_ACS	0x0002	/* ACS Function Groups Capability */
+#define  PCI_ARI_CAP_NFN(x)	(((x) >> 8) & 0xff) /* Next Function Number */
+#define PCI_ARI_CTRL		0x06	/* ARI Control Register */
+#define  PCI_ARI_CTRL_MFVC	0x0001	/* MFVC Function Groups Enable */
+#define  PCI_ARI_CTRL_ACS	0x0002	/* ACS Function Groups Enable */
+#define  PCI_ARI_CTRL_FG(x)	(((x) >> 4) & 7) /* Function Group */
 
 #endif /* LINUX_PCI_REGS_H */