[PATCH] PCI: support PCIe ARI capability

[Yu Zhao]

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.

This patch is based on a cleanup patch (centralize the capabilities
code in probe.c) I sent before.

Signed-off-by: Yu Zhao <***@intel.com>

---
drivers/pci/pci.c | 32 ++++++++++++++++++++++++++++++++
drivers/pci/pci.h | 12 ++++++++++++
drivers/pci/probe.c | 3 +++
include/linux/pci.h | 1 +
include/linux/pci_regs.h | 14 ++++++++++++++
5 files changed, 62 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d2ea576..9165615 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1278,6 +1278,38 @@ 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)
{
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 05519d2..69b6365 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -150,4 +150,16 @@ 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 */
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ae0ce6d..dcd6bf1 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1019,6 +1019,9 @@ 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)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index cc78be6..26a1ee1 100644
--- a/include/linux/pci.h
+++ b/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;
diff --git a/include/linux/pci_regs.h b/include/linux/pci_regs.h
index 450684f..eb6686b 100644
--- a/include/linux/pci_regs.h
+++ b/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 */

[Jesse Barnes]

Post by Yu Zhao
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.
This patch is based on a cleanup patch (centralize the capabilities
code in probe.c) I sent before.

Applied, thanks.

Jesse